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A Systematic Review of Home-Based Childhood Obesity Prevention Studies

Nakiya n. showell.

a Division of General Pediatrics, Department of Pediatrics;

Oluwakemi Fawole

b Johns Hopkins University Evidence-based Practice Center, Baltimore, Maryland;

d Division of General Internal Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland;

c Department of Health Policy and Management;

Renee F. Wilson

Lawrence j. cheskin.

e Department of Health, Behavior and Society, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; and

Sara N. Bleich

f Johns Hopkins Global Center on Childhood Obesity, Department of International Health, Center for Human Nutrition, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland

Brandyn Lau

Background and objectives:.

Childhood obesity is a global epidemic. Despite emerging research about the role of the family and home on obesity risk behaviors, the evidence base for the effectiveness of home-based interventions on obesity prevention remains uncertain. The objective was to systematically review the effectiveness of home-based interventions on weight, intermediate (eg, diet and physical activity [PA]), and clinical outcomes.

We searched Medline, Embase, PsychInfo, CINAHL, clinicaltrials.gov, and the Cochrane Library from inception through August 11, 2012. We included experimental and natural experimental studies with ≥1-year follow-up reporting weight-related outcomes and targeting children at home. Two independent reviewers screened studies and extracted data. We graded the strength of the evidence supporting interventions targeting diet, PA, or both for obesity prevention.

We identified 6 studies; 3 tested combined interventions (diet and PA), 1 used diet intervention, 1 combined intervention with primary care and consumer health informatics components, and 1 combined intervention with school and community components. Select combined interventions had beneficial effects on fruit/vegetable intake and sedentary behaviors. However, none of the 6 studies reported a significant effect on weight outcomes. Overall, the strength of evidence is low that combined home-based interventions effectively prevent obesity. The evidence is insufficient for conclusions about home-based diet interventions or interventions implemented at home in association with other settings.

CONCLUSIONS:

The strength of evidence is low to support the effectiveness of home-based child obesity prevention programs. Additional research is needed to test interventions in the home setting, particularly those incorporating parenting strategies and addressing environmental influences.

Childhood obesity has become a major public health epidemic. 1 – 3 At present, more than one-third of American children and adolescents are overweight or obese, reflecting a nearly threefold increase in obesity prevalence since 1980. 3 , 4 The consequences of obesity are numerous. Overweight children are more likely to become obese adults. 5 Additionally, overweight children are disproportionately affected by adverse physical and psychosocial health outcomes, including hypertension, diabetes, low self-esteem, and increased engagement in high-risk behaviors. 6 , 7

It is widely recognized that the family and home environment significantly influence child diet and physical activity (PA) behaviors. 8 , 9 Three recent systematic reviews have highlighted the importance of these influences on child obesity prevention and treatment, mainly for young children. 10 – 12 A 2011 review identified studies that supported a small to moderate effect of parenting interventions on weight-related outcomes. 10 Another 2011 review identified studies that reported a favorable effect of key parental variables (eg, parental feeding practices, parental style, etc) on risk behaviors for child obesity in preschool-aged children. 11 The third review reported that the majority of studies reported a favorable effect of family and home-based interventions on the treatment of overweight and obesity among young children aged 2 to 7 years. 12

To additionally examine the evidence base for the effectiveness of home-based prevention programs on child obesity, our team completed an Agency for Healthcare Research and Quality–funded systematic review on childhood obesity prevention studies conducted in high-income countries. The present report represents a component of our larger systematic review of childhood obesity prevention studies. 13 The larger systematic review addresses 6 key questions (KQs 1-6) evaluating the effectiveness of obesity prevention programs conducted in various settings for the prevention of obesity or overweight in children. This article describes the results of home-based obesity prevention studies (KQ2). Findings addressing other KQs are available in our full evidence report.

We developed and followed a standard protocol for this review following the recommended methods as described in the Methods Reference Guide for Effectiveness and Comparative Effectiveness Reviews . 14 Additional details of the protocol are available in our full evidence report. 13

Literature Search Strategy

We searched Medline, Embase, PsychInfo, CINAHL, clinicaltrials.gov, and the Cochrane Library through August 11, 2012, and identified additional studies from reference lists of eligible articles and relevant systematic reviews. Our electronic search strategy included medical subject headings (MeSH) and keywords related to childhood obesity and overweight prevention. We also conducted a gray literature search in clinicaltrials.gov to identify unpublished research that was relevant to our review on July 23, 2012.

Study Selection

We identified studies conducted in high-income countries that reported the effects of interventions to prevent obesity in children and adolescents aged 2 to 18 years old. We included randomized controlled trials, quasi-experimental studies, and natural experimental studies with at least 1-year follow-up that targeted children in their homes or included significant family involvement. Interventions of interest involved a modification of diet, PA, sedentary behaviors, or a combination of these. Additionally, the study was required to report the effect(s) of the intervention on weight-related outcomes. We excluded studies that targeted only overweight or obese children or children with preexisting medical conditions such as diabetes or heart disease.

Data Extraction and Quality (Risk of Bias) Assessment

Two reviewers independently screened first the abstract and then the full article for eligibility ( Fig 1 ). One reviewer abstracted data from included articles and a second reviewer checked the abstracted data for accuracy. We abstracted information on study characteristics, study participants, eligibility criteria, interventions, outcome measures, the method of ascertainment, and the outcomes. We assessed the quality of included studies by using the Downs & Black instrument. 15 We categorized the studies as having low, moderate, or high risk of bias. We rated a study as having a low risk of bias only when it had met all of the following requirements:

Additionally, the study had to have at least partially described the distributions of (potential) principal confounders in each treatment group.

An external file that holds a picture, illustration, etc.
Object name is peds.2013-0786fig01.jpg

Results of the literature search on home-based childhood obesity prevention studies in high-income countries. a Sum of excluded abstracts exceeds 5600 because reviewers were not required to agree on reasons for exclusion. b Sum of excluded articles exceeds 470 because reviewers were not required to agree on reasons for exclusion. KQ, key question.

Outcome Variables

We compared the effects of interventions on weight- or body composition–related outcomes (eg, BMI, BMI z score, weight), obesity-related clinical outcomes (eg, blood pressure, lipids), intermediate outcomes (dietary intake, PA), and adverse effects of interventions. Body composition–related outcomes were our primary focus. Outcomes were either compared between 2 groups, both of which received an intervention, or 2 groups, 1 of which received the intervention and the other usual care or no intervention.

Data Synthesis and Analysis

We created a set of detailed evidence tables containing all information abstracted from eligible studies. Results were first organized by setting or combination of settings where the intervention took place (eg, home, school settings or home, community settings, etc) and then by intervention. We described the interventions on the basis of their focus (eg, change in dietary intake or PA) and the modality of intervention delivery (eg, education, environment modification, or self-management technique). We reviewed studies for outcomes of relevant subgroups (eg, age, gender, race), and reported them separately by subgroup.

We present qualitative summaries of included studies in this review. Due to intervention and outcome heterogeneity, meta-analyses could not be conducted.

Strength of the Evidence

We graded the quantity, quality, and consistency of the best available results or evidence by adapting an evidence-grading scheme recommended in the Methods Reference Guide for Effectiveness and Comparative Effectiveness Reviews . 14 We classified evidence into 4 categories:

Search Results

We identified 34 545 unique citations. During the title screening, we excluded 28 344 citations, and excluded an additional 5600 during abstract screening. During article screening, we excluded an additional 470 articles. Six studies reporting on home-based interventions (KQ2) were included in this review: 3 home-based combined (diet and PA) intervention studies, 16 – 18 1 home-based diet intervention study, 19 1 combined home-based study with primary care and consumer health informatics components, 20 and 1 combined home-based study with school and community components ( Fig 1 ). 21 The results of the gray literature search did not yield studies eligible for inclusion in this review.

Description of Included Studies

Study characteristics are summarized in Table 1 . All studies were randomized controlled trials conducted in the United States. 16 – 21 The majority of included studies were conducted exclusively in the home setting ( n = 4). 16 – 19 The sample size of included studies ranged from 26 to 1323 participants. Intervention length varied between 14 and 104 weeks, and participant follow-up ranged from 52 to 104 weeks. One study specifically targeted girls, 19 and 2 other studies targeted preschool- 18 and adolescent-aged participants ( Table 1 ). 20

Summary of the Results of Home-Based Childhood Obesity Prevention Studies Conducted in High-Income Countries on Weight-Related Outcomes

CI, confidence interval; D, diet; NR, not reported; NS, not significant; RCT, randomized controlled trial. —, results not reported.

Overall Findings on the Effectiveness of Home-Based Interventions

The results of home-based obesity interventions on weight-related and intermediate outcomes are summarized in Tables 1 and ​ and2, 2 , respectively. None of the 6 studies reported a significant intervention effect on weight-related outcomes, whereas 3 reported statistically significant effects of a combined intervention on fruit/vegetable intake 17 , 21 or sedentary behaviors. 20 No studies reported on clinical outcomes or adverse effects of the interventions.

Summary of the Results of Home-Based Childhood Obesity Prevention Studies Conducted in High-Income Countries on Intermediate Outcomes

CI, confidence interval; D, diet; MVPA, moderate-to-vigorous PA; NR, not reported; NS, not significant; RCT, randomized controlled trial; —, results not reported.

Effectiveness of Home-Based Interventions by Setting(s) and Intervention Type

Home-based diet and pa interventions.

Three randomized controlled trials tested such interventions over a 52-week study period. 16 – 18 These studies enrolled a total of 262 participants aged 4 to 17 years. One reported on the effect of 2 educational diet and PA interventions, each targeting a different dietary behavior (increased fruit and vegetable intake versus decreased intake of high-fat/high-sugar foods). 16 The second study evaluated the effect of the intervention on television viewing, snack/sweet intake, eating out, and PA among entire households. 17 The third study assessed the effect of the intervention on dietary fat, fruit and vegetable intake, television viewing, and PA among preschool-aged children. 18

None of these studies reported significant beneficial intervention effects on BMI, BMI z score, weight, or prevalence of obesity/overweight. 16 – 18

With regard to intermediate outcomes, in 2 studies there were no differences between the intervention and control groups in minutes per day of PA, television viewing, or general screen time. 17 , 18 All 3 studies 16 – 18 reported a favorable intervention effect on fruit and vegetable intake, but only 1 study reported a statistically significant intervention effect on fruit and vegetable intake ( P = .05). 17 In 1 study there was no difference in sugar-sweetened beverage intake between the intervention and control groups. 17 Similarly, another study reported no difference between the intervention and control groups in energy intake. 18

The strength of evidence is low to conclude that combined diet and PA interventions in a home setting prevent child obesity. We graded the strength of evidence as low because it included 3 moderate to high risk of bias studies that were inconsistent (1 reported a favorable but not statistically significant effect, 2 reported a negative effect) and imprecise ( Table 3 ).

Summary of the Strength of Evidence for Weight-Related Outcomes in Studies Taking Place in the Home

C, combination of diet and PA interventions; D, diet; CHI, consumer health informatics; NA, not applicable; PC, primary care.

Home-Based Diet Intervention

One randomized controlled trial reported on an educational diet intervention that randomly assigned 59 girls to intervention and control groups. 19 This study included only 9-year-old girls with a BMI <85th percentile. The study evaluated the effect of a calcium-rich diet on weight gain over a 104-week study period.

There was no reported difference in BMI at 104 weeks between the intervention and control arms. 19 Similarly, there was no reported difference in fat mass or weight at 104 weeks between the intervention and control arms and no difference in reported hours of PA. At 104 weeks, the intervention group had a higher total energy intake compared with the control group. However, this between-group difference was not significant. 19

Home-, Primary Care–, and Consumer Health Informatics–Based Diet and PA Intervention

A single study enrolled 878 participants aged 11 to 15 years. The intervention targeted diet and PA behaviors by using several modalities: computer-supported assessment, provider counseling, monthly mail and telephone counseling, and family participation.

The study did not find a significant difference in BMI z score at 52 weeks between the intervention and control arms among all participants or among participants with a BMI ≥95th percentile. 20 It also did not find significant differences in minutes per week of moderate plus vigorous PA, percentage of calories from fat, or fruit and vegetable intake between the intervention and control groups. However, the intervention resulted in a significant decrease in hours per day of sedentary behaviors among boys and girls ( P = .001).

Home-, School-, and Community-Based Diet and PA Intervention

One randomized controlled trial evaluated such an intervention on weight and intermediate outcomes at 34 and 61 weeks. 21 This study was conducted in the United States and enrolled 1323 participants with a mean age of 9.6 years. The intervention targeted 3 behaviors at the family, school, and community levels: increase in fruit and vegetable intake, increase in PA, and decrease in screen time.

There was no overall difference in BMI between the control and intervention groups at the 34- or 61-week follow-up. However, when analyzed by gender, boys had significantly lowered BMI due to the intervention ( P < .05). 21

There was no statistically significant difference in PA or screen time between the intervention and control groups at either follow-up time period. 21 However, children in the intervention group reported significantly more fruit and vegetable consumption compared with the control group at 61 weeks ( P < .05). 21

We identified 6 childhood home-based obesity prevention studies conducted in high-income countries. The majority of them ( n = 4) were conducted exclusively in the home setting. The remaining studies included intervention components implemented in other settings such as the school and local community.

Overall, none of the home-based interventions revealed a statistically significant desirable effect on weight-related outcomes such as BMI and prevalence of overweight/obesity. However, 3 studies assessed and reported significant desirable intervention effects on diet or PA outcomes. 17 , 20 , 21 There were several characteristics of these 3 studies that may have contributed to their beneficial effect on intermediate outcomes. Two of these studies included significantly larger sample sizes ( N = 878, N = 1323) of participants in comparison with the other home-based interventions. 20 , 21 These same studies also tested the effect of intervention components implemented in other settings (eg, school, community, primary care settings), which may enhance their effectiveness on behavior change by virtue of their greater reach to targeted participants. Finally, one of the studies targeted entire families in households. 17 Hence, the intervention’s effect on child dietary intake may have been facilitated through direct modification of the physical home environment and emphasis on family involvement.

Despite demonstration of favorable effects on intermediate outcomes, none of the 6 studies included in our review reported a significant overall effect on weight-related outcomes. This finding suggests that longer intervention duration and/or greater intensity of intervention dose may be necessary to fully realize the impact of the interventions on weight-related outcomes. Second, many of the included studies targeted individual behavior change without concurrent modifications to the child’s food environment (eg, increased availability of healthful foods) or PA environment (eg, increased access to neighborhood recreational space, neighborhood walkability). It is widely recognized that environmental factors such as these may influence child obesity risk. 22 – 24 Therefore, without systematically addressing physical environmental factors and their potential influence on individual-level behaviors, the impact of interventions on obesity-risk behaviors and resultant obesity may be attenuated. Finally, the inclusion of studies with small sample sizes and studies that did not primarily aim to prevent obesity may have also contributed to the lack of treatment effect observed.

This review has several key strengths. We used a systematic and rigorous review process to identify the relevant literature, as standardized by the Agency for Healthcare Research and Quality. Additionally, we evaluated the effects of the interventions on multiple outcomes including weight-related outcomes and behavioral outcomes and used a widely accepted grading scheme to grade study quality and strength of evidence.

Several factors also limited our review. We identified only 6 studies, and due to the considerable heterogeneity in populations, approaches, outcomes, and measurement tools among studies, we were unable to conduct a quantitative synthesis of the literature. Additionally, we limited our review to diet and PA intervention studies with at least 1 year of follow-up and only included those from high-income countries. Hence, we excluded some studies with potentially useful interventions (eg, parenting interventions). However, many of these studies have been included in other, more general, systematic reviews. 10 , 11 , 25 Finally, we excluded interventions that were primarily conducted in other settings but included components conducted in the home setting (eg, school- and home-based interventions), because these interventions may differ from those included in this review and hence limit the ability to collectively examine their effectiveness on child obesity prevention. Details of the findings from these other studies are available in our full evidence report.

Our study contributes valuable information to the existing literature on home-based obesity interventions. In comparison with other recent systematic reviews that examined the effect of parenting or treatment interventions mainly among young children, 10 – 12 this review systematically assessed the impact of diet or diet and PA interventions on prevention of obesity among children and adolescents. On the basis of the paucity of the evidence, however, it is clear that more research is needed to evaluate the impact of home- and family-based interventions on child obesity. Specifically, additional research is needed to test home-based interventions with larger sample sizes, greater intervention duration and intensity, and adequate participant follow-up to improve statistical power of studies. Given the important role parenting plays on child behaviors and the demonstrated effectiveness of parenting intervention components on weight-related outcomes and obesity risk, 11 , 26 widespread integration of parenting strategies in home-based interventions should also be considered and additionally evaluated. Finally, implementing and testing the effectiveness of home-based interventions that address important physical environmental influences on obesity-risk behaviors should be a priority of the child obesity research agenda.

Conclusions

Only a small number of studies examined childhood obesity prevention programs in the home setting. The strength of evidence is low, at best, to support the effectiveness of home-based programs on childhood obesity prevention. Additional research is needed to test interventions in the home setting, particularly those integrating parenting and addressing important environmental sources of influence.

Acknowledgments

We thank Mr Allen Zhang for his technical assistance with this report. We also thank all of the members of the Johns Hopkins University Evidence-based Practice Center who assisted with data abstraction and analysis for this project.

Dr Showell participated in data acquisition and data analysis, wrote the first draft of the manuscript, revised subsequent drafts of the manuscript, and approved the final manuscript as submitted; Drs Fawole and Bleich, Ms Wu, and Mr Lau participated in data acquisition and data analysis, reviewed drafts of the manuscript, and approved the final manuscript as submitted; and Drs Segal, Cheskin, and Wang and Ms Wilson conceptualized and designed the study, reviewed drafts of the manuscript, and approved the final manuscript as submitted.

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.

FUNDING: This project was funded under contract 290-2007-10061-I from the Agency for Healthcare Research and Quality, US Department of Health and Human Services. Drs Wang, Cheskin, and Wu’s efforts in the study were also supported by a childhood obesity–related center grant from the Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD; U54HD070725), which is cofunded by the NICHD and the Office of Behavioral and Social Sciences Research at the National Institutes of Health. Dr Showell was supported by an Agency for Healthcare Research and Quality, Comparative Effectiveness Development Training grant T32 HS19488-01. The content is solely the responsibility of the authors and does not necessarily represent the official views of the funders. Funded by the National Institues of Health (NIH).

COMPANION PAPER: A companion to this article can be found on page e201, online at www.pediatrics.org/cgi/doi/10.1542/peds.2013-0886 .

A systematic review and meta-analysis of the overall effects of school-based obesity prevention interventions and effect differences by intervention components

International Journal of Behavioral Nutrition and Physical Activity volume  16 , Article number:  95 ( 2019 ) Cite this article

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Childhood obesity is a serious public health concern . School-based interventions hold great promise to combat the rising trend of childhood obesity. This systematic review aimed to assess the overall effects of school-based obesity prevention interventions, and to investigate characteristics of intervention components that are potentially effective for preventing childhood obesity.

We systematically searched MEDLINE, CENTRAL and Embase databases to identify randomized- or cluster randomized- controlled trials of school-based obesity interventions published between 1990 and 2019. We conducted meta-analyses and subgroup analyses to determine the overall effects of obesity prevention programs and effect differences by various characteristics of intervention components on body mass index (BMI) or BMI Z-score of children.

This systematic review included a total of 50 trials (reported by 56 publications). Significant differences were found between groups on BMI (− 0.14 kg/m 2 (95% confidence interval: − 0.21, − 0.06)) and BMI Z-score (− 0.05 (− 0.10, − 0.01)) for single-component interventions; significant differences were also found between groups on BMI (− 0.32 (− 0.54, − 0.09) kg/m 2 ) and BMI Z-score (− 0.07 (− 0.14, − 0.001)) for multi-component interventions. Subgroup analyses consistently demonstrated that effects of single-component (physical activity) interventions including curricular sessions (− 0.30 (− 0.51, − 0.10) kg/m 2 in BMI) were stronger than those without curricular sessions (− 0.04 (− 0.17, 0.09) kg/m 2 in BMI); effects of single-component (physical activity) interventions were also strengthened if physical activity sessions emphasized participants’ enjoyment (− 0.19 (− 0.33, − 0.05) kg/m 2 in BMI for those emphasizing participants’ enjoyment; − 0.004 (− 0.10, 0.09) kg/m 2 in BMI for those not emphasizing participants’ enjoyment). The current body of evidence did not find specific characteristics of intervention components that were consistently associated with improved efficacy for multi-component interventions ( P  > 0.05).

Conclusions

School-based interventions are generally effective in reducing excessive weight gain of children. Our findings contribute to increased understandings of potentially effective intervention characteristics for single-component (physical activity) interventions. The impact of combined components on effectiveness of multi-component interventions should be the topic of further research. More high-quality studies are also needed to confirm findings of this review.

Introduction

Childhood overweight and obesity are global public health issues. The prevalence has increased from 16.9 to 23.8% in boys and from 16.2 to 22.6% in girls from 1980 to 2013 in developed countries, while in developing countries, the prevalence has also increased from 8.1 to 12.9% in boys and 8.4 to 13.4% in girls [ 1 ]. Childhood obesity is associated with a variety of adverse consequences [ 2 , 3 ], which often persist into adulthood [ 4 ]. Therefore, prevention of childhood obesity has become one of the important public health priorities.

The main cause of childhood overweight and obesity is an energy imbalance between calories consumed and calories expended. Children spend half of their waking hours and consume at least one-third of their daily calories at school, and thus schools are being recognized as ideal vehicles for delivering obesity interventions to most children [ 5 ].

Based on the Environmental Research framework for weight Gain prevention as well as an energy balance approach [ 6 ], the goal of obesity prevention might be achieved by improvement of energy balance-related behaviors (physical activity (PA)), dietary improvement (DI)), which can be influenced by environmental influence (school policy (SP)) directly or indirectly. The direct influence reflects the “automatic, unconscious” influence of the SP on behavior. The indirect mechanism reflects the mediating role of knowledge, cognitions related to behavior (health education (HE)) in the influence of the environment on behavior. As such, a range of intervention components (PA, DI, SP, HE) have been widely used in childhood obesity prevention interventions.

Notably, a great deal of variability existed in the frequency, duration and content of intervention components [ 5 , 7 , 8 ]. For instance, some school-based interventions focused on increasing students’ daily physical activity [ 9 , 10 ], while others only increased the frequency of physical activity by 2–3 times/week [ 11 , 12 ]. Topics of health education interventions also varied. Some focused primarily on nutrition education with few physical activity or sedentary behaviors education [ 13 , 14 ], some mainly on physical activity or sedentary behaviors education with few nutrition education [ 15 , 16 ], while others covered both physical activity and nutrition education [ 9 , 17 ]. The variety of characteristics of intervention components raises the question of what is specifically associated with intervention efficacy.

Previous reviews attempted to address question of this kind and revealed some general findings. That is, interventions covering multiple components and involving families tended to be effective [ 5 , 6 ]. Three issues remained yet. First, some reviews only summarized intervention components that were commonly used in previous trials [ 5 , 18 ], but they did not compare various components used in effective or non-effective trials. In other words, the identified components could be used in both effective and non-effective trials, so that the exact components uniquely related to intervention effectiveness were still unknown. Second, a previous review, focusing on the specific role of behavior change techniques, summarized “effectiveness ratio” which was determined by the ratio of intervention components used in effective trials relative to those used in both effective and non-effective trials [ 19 ]. However, the trials included in the review were weighted equally by this approach regardless of the sample size and standard error of the outcomes. Third, another review compared sub-group differences in effect sizes between trials with and without the intervention characteristics by using meta-analytic technique [ 20 ]. However, to our knowledge, this approach has not been used in specifying the effective intervention components in school-based obesity prevention interventions.

To fill the research gaps in this field, we conducted a systematic review and meta-analysis of the best available evidence from randomized controlled trials (RCT). This review aimed to firstly summarize the overall effect size of school-based obesity prevention interventions, and secondly to explore characteristics of intervention components that were associated with the improved intervention efficacy.

Literature search

We systematically searched three databases including MEDLINE, CENTRAL and Embase to identify RCTs of school-based obesity interventions. We included publications between January 1990 and July 2019. Our searching strategy primarily contained terms in relation to participants, interventions, body weight and study design. The full search strategy was attached in the online supporting document. The reference lists of all retrieved full text reviews were further searched for additional relevant publications. The date for our final search was July 8th, 2019.

Inclusion criteria for this review were: (1) individual- or cluster-RCT, (2) interventions implemented among students of elementary or secondary schools (aged 5~18 years), (3) studies assessing students’ body mass index (BMI) or BMI Z-score, (4) anthropometric data being collected by physical examination, (5) interventions lasting for at least 3 months, (6) intervention groups aiming for promoting healthy weight or prevention of overweight or obesity rather than treatment of overweight or obesity, (7) comparison groups being active controls, usual practice controls (maintaining “normal” school activities) or wait-list controls, (8) the English version of full-text publications available (for pragmatic reasons), as well as (9) studies providing data for meta-analyses (means, standard deviations (SDs) or 95% confidence intervals (CIs)).

Exclusion criteria included (1) studies only using questionnaires to collect the adiposity outcomes, and (2) studies specifically designed for the treatment of obesity-related diseases (e.g., type 2 diabetes or hypertension).

Screening and data extraction

First, two reviewers (HMX; YZP) independently screened the titles and abstracts of publications obtained by the searches. Second, full texts were further identified for their eligibility. Reference lists of reviews were additionally checked for their eligibility. Discrepancies between the two reviewers (HMX; YZP) were discussed by themselves or with a third reviewer (ZL) and resolved with consensus.

The first reviewer (ZL) developed a detailed coding scheme, and the extraction items included authors, year of publication, study design, sample size, age of participants, percentages of female participants, components and characteristics of interventions, outcome measures and assessment of risk of bias. The components and characteristics of interventions were extracted from both the main papers and the intervention protocols [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Authors were further contacted for details that were not reported in the publications (in three cases). A second reviewer (HMX) independently extracted data from all the included studies, and 20% of the extracted data were double checked by the first reviewer (ZL). Disagreements in relation to data extraction were resolved by a brief discussion (kappa statistics: 0.62; in five cases).

Assessment of risk of bias

Risk of bias of individual studies was assessed following the Cochrane guidance [ 31 ]. The assessment contains the following domains including (1) random sequence generation ( whether or not the study used a randomized sequence of assignments ), (2) concealment of the allocation sequence ( whether or not the allocation sequences were protected by adequate concealment ), (3) blinding of participants and personnel ( whether or not participants or healthcare providers were aware of intervention assignments ), (4) blinding of outcome assessment ( whether or not people who determined outcome measurements were aware of intervention assignments ), (5) incomplete outcome data ( the possibility of bias due to missing outcome data ), (6) selective outcome reporting ( whether or not the results reported were consistent with the original variables in the protocol ) and (7) other bias ( the possibility of bias not reported in the previous domains ). The leading author (ZL) was responsible for training the other author (HMX) to ensure a consistent understanding of the evaluation criteria of risk of bias between the two authors (ZL; HMX). Each domain was rated as having a high, low or unclear risk of bias. We also paid particular attention to the use of statistical methods specific to cluster-randomized trials (whether or not considering the cluster effect), and rated them in the domain of other bias.

Data synthesis

We calculated differences in means of BMI and BMI Z-score between intervention and control groups that were reported change from baseline or follow-up BMI indices controlled for baseline measures. If the trials reported data at both immediately post-intervention and subsequent follow-ups, only the data at immediately post-intervention was included in the meta-analyses (as most of the included studies did not report the sustained effect of interventions).

As we expected considerable heterogeneity across studies, the random-effects model was used to pool the weighted results by inverse variance methods. We used the I 2 statistic to provide a measure of heterogeneity. Results with P  < 0.05 are reported as significant. The level of heterogeneity across studies were rated as low (I 2  = 25%), moderate (I 2  = 50%) or high (I 2  = 75%). We used Stata/SE 15.0 (StataCorp) for all analyses.

Subgroup analyses

To identify the characteristics of interventions potentially contributing to the improved effects, we first categorized interventions into those having the specified intervention components (i.e., SP, HE, PA and DI) and those without these. Then, we classified interventions into those using single or multiple components, as their effect sizes were detected as significantly different in previous reviews [ 6 , 32 ]. Further, we used subgroup analyses to examine differences in effect sizes by inclusion of SP related to obesity prevention (for multi-component interventions; yes vs. no), whether or not topics in HE covering both energy input and expenditure (for both single- and multi-component interventions; yes vs. no), duration and frequency of PA (for both single- and multi-component interventions; ≥3 times/week and ≥ 10 min/time vs. < 3 times/week or < 10 min/time), whether or not including curricular PA (for both single- and multi-component interventions; yes vs. no), whether or not focusing on students’ enjoyment of PA (for both single- and multi-component interventions; yes vs. no), and whether or not including the DI component (for multi-component interventions; yes vs. no).

Sensitivity analyses

We conducted sensitivity analyses for the following considerations:

1. If heterogeneity in the meta-analyses was moderate or high, we additionally obtained the pooled results by excluding individual studies for which the 95% CI of the intervention effect does not overlap with others.

2. We compared the pooled results obtained by all studies with those excluding individual studies at high risk of bias.

3. We grouped all comparisons according to characteristics of the study population ( sex : exclusively boys, exclusively girls; weight status at baseline : not overweight or obesity, overweight or obese; country : middle-income countries, high-income countries). If a minimum of 2 studies (data available) was included in each group, we would further conduct sub-group analyses to investigate whether intervention effectiveness differed within sub-groups.

Assessment of publication bias

We assessed the possibility of publication bias by drawing funnel plots. We recognized that asymmetry of funnel plots can be due to publication bias or a genuine relationship between effect size and trial size. There were a minimum of 10 studies required for the meaningful interpretation of funnel plots. We also conducted Egger’s regression test to more definitely ascertain whether publication bias was present.

Literature screening

We identified 12,614 relevant records, and 2866 were excluded due to duplicates. The titles or abstracts of 9748 records were then screened and 456 full-text articles were further checked for their eligibility. Finally, 50 trials (involving 63,734 children) reported by 56 articles [ 9 , 12 , 13 , 14 , 15 , 16 , 17 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 ] that met the eligibility criteria were included in this review. The flowchart of screening process is presented in Fig.  1 . The list of excluded studies is shown in Additional file  1 : Table S8.

figure 1

Study flow of the review

Characteristics of included trials

Characteristics of the included trials are demonstrated in Table  1 and Additional file 1 : Tables S1-S3. Most of them ( n  = 47, 94%) were cluster RCTs using the school or class as the unit of randomization. All studies had one arm as the intervention group with exception of three studies [ 35 , 57 , 64 ]. All studies used usual practice controls except one using an active control, in order to mitigate the potential of the Hawthorne effect [ 13 ]. A large proportion of the studies were implemented in high-income countries ( n  = 40, 80%). Most of them ( n  = 43, 86.0%) were implemented exclusively in elementary schools (mean age: 8.1 years). The follow-up period of trials ranged from 3 months to 6 years, and more than half ( n  = 32, 64%) of them maintained shorter than 12 months.

Thirty-five (70%) interventions were multi-component while others adopted single component. HE ( n  = 7) or PA ( n  = 7) was mostly used among single-component interventions. The combinations of components mostly used in multi-component interventions were PA + HE+/−SP ( n  = 10; “+/−”: with or without), and PA + HE+DI+/−SP ( n  = 8), followed by HE+DI+/−SP ( n  = 7), HE+SP ( n  = 5), PA + DI+/−SP ( n  = 3), and PA + SP ( n  = 2).

Assessment of risk of bias was summarized in Fig.  2 . Most of the trials ( n  = 47, 98%) were assessed as having a low risk of bias in allocation concealment. And most of the trials ( n  = 49, 98%) were judged as having a high risk of bias in blinding of participants and (or) personnel because it was usually not possible for interventions of this nature. Approximately half of the studies were assessed as having an unclear risk of bias due to insufficient descriptions in terms of random sequence generation ( n  = 30, 60%), blinding of outcome assessment ( n  = 25, 50.0%), incomplete outcome data ( n  = 27, 54%) or the possibility of selective reporting ( n  = 32, 64%).

figure 2

Risk of bias graph

Overall effect size

Overall effect size was summarized in Figs.  3 and 4 . The quantitative synthesis of the single-component interventions showed a significant, but small reduction of 0.14 (95% CI: 0.06, 0.21) kg/m 2 in BMI, and a small reduction of BMI Z-score (0.05, 95% CI: 0.01, 0.10) compared with the control group. For the multi-component interventions, the pooled results showed a significant, but mild reduction of 0.32 (0.09, 0.54) kg/m 2 in BMI, and 0.07 (0.001, 0.14) in BMI Z-score compared with the control group. Although the pooled effect sizes in BMI indices of multi-component interventions were slightly larger than that of single-component interventions, the differences were not statistically significant ( P  = 0.41 for BMI, P  = 0.71 for BMI Z-score).

figure 3

Pooled intervention effect (BMI)

figure 4

Pooled intervention effect (BMI Z-score)

Findings of overall effect size were robust to the exclusion of heterogeneous studies or studies of high risk of bias (Additional file 1 : Figures S1-S3). Results were also not significantly different across sex, weight status and country of the study population (Additional file 1 : Table S4).

Subgroup analyses showed that means of BMI differed significantly by whether or not studies including curricular PA sessions or emphasizing enjoyment in PA among single-component interventions (Table 2 ). The pooled BMI from single-component interventions including curricular PA ( n  = 3) was − 0.30 (95% CI: − 0.51, − 0.10) kg/m 2 , while the effect size from single-component interventions not including curricular PA ( n  = 4) was − 0.04 (95% CI: − 0.17, 0.09) kg/m 2 . The pooled BMI from interventions focusing on enjoyment of participants during PA ( n  = 5) was − 0.19 (95% CI: − 0.33, − 0.05) kg/m 2 , while the effect size for interventions not emphasizing enjoyment of participants ( n  = 2) was − 0.004 (95% CI: − 0.10, 0.09) kg/m 2 . The effect sizes did not differ significantly on other intervention characteristics among single-component interventions ( P  > 0.05). Findings of subgroup analyses for single-component interventions were consistent with results from sensitivity analyses (Additional file 1 : Table S6).

Concerning multi-component interventions, subgroup analyses demonstrated that the mean BMI or BMI Z-score differed significantly by interventions emphasizing enjoyment in PA (Table  3 ); however, this difference was disappeared when excluding one heterogeneous study (Additional file 1 : Table S5). No significant differences in effect sizes ( P  > 0.05) were detected between multi-component interventions with and without other intervention characteristics, which was consistent with results from sensitivity analyses (Additional file 1 : Table S5, S7).

As shown in Fig.  5 , the funnel plot of the observed effect showed a slightly asymmetric scatter consistent with publication bias, but P value for Egger’s regression test was larger than 0.05.

figure 5

Assessment of publication bias: funnel plot

This review is one of the first to use meta-analyses and subgroup analyses to systematically review a number of more recent studies, and analyze the potentially effective characteristics of school-based interventions for preventing obesity.

Interpretation of the study findings

This review found that emphasizing enjoyment in PA sessions was critical for single-component (PA) interventions. This finding was echoed by previous reviews suggesting that lack of motivation and pleasure of physical activity was a barrier to physical activity for children [ 82 , 83 ]. Including curricular PA sessions was also found to be associated with improved efficacy of single-component (PA) interventions. This is, at least partly, explained by the fact that curricular PA sessions were usually led by physical education teachers, and thus intensity of exercise was superior to those including only extracurricular activities, after-school sessions or short activity breaks. Further, the curricular PA sessions were usually structured and compulsory for all children in a class and thus adherence could be relatively guaranteed. Significant associations between intervention components and efficacy were not consistently found in multi-component interventions. It is likely that multi-component interventions demonstrated to be effective were influenced by a combination of intervention components. The impact of combining components on intervention effectiveness should be the topic of further research.

For the current body of evidence, we did not find significant associations between dietary improvement components with improved intervention efficacy. This finding was consistent with another recent systematic review of school-based childhood obesity interventions [ 84 ]. The non-significant finding in relation to diet might be interpreted by poor adherence to diet intervention or the complex interplay of intervention components. We acknowledge that interaction analyses of intervention components (“intervention × component”) within individual studies would have provided a powerful method of understanding the complex interplay of intervention components. However, of the studies screened for this review, none reported such “intervention × component” analyses. Therefore, future obesity prevention interventions should address the specific interplay of intervention components, providing the possibility for further systematic reviews.

Findings of the study should also be interpreted in the context. The reporting of intervention characteristics (dose, frequency, and content) varied so much between trials that we were obliged to dichotomise it simply as “including the specific characteristics of component: yes/no” for the purpose of analysis, being nevertheless aware that resolution of the measure might be compromised in the process.

Comparison with other studies

Some previous reviews of obesity interventions have attempted to address the question of “what” (characteristics or components of interventions) really works for the targeted population [ 5 , 17 , 18 ], but only general findings were revealed. Further, research gaps remained in relation to the weakness of methods that were used (i.e., no comparisons between effective and non-effective trials; equal weighting of the included trials). The present review not only provided an update on a recent review [ 5 ] by including several new studies, but also identified the characteristics of effective interventions through meta-analyses and subgroup analyses. Thus, this review provides important and helpful evidence of the potentially effective intervention components with different characteristics.

Limitations and strengths of the study

Our results should be weighted cautiously considering the following limitations. First, the studies included in this review were restricted to English full-text publications found in three electronic databases. Second, the considerable level of heterogeneity was detected across studies in this review, which is relatively common among complex obesity interventions. Heterogeneity might be originated from the fidelity of the intervention and the population targeted among other factors. We have conducted sensitivity analyses to address this concern. Third, precisely evaluating the contents of some interventions is difficult and problematic due to inconsistent reporting. Future trials should be required to report interventions in accordance with TIDieR (template for intervention description and replication) [ 85 ] or other tools. Fourth, solely using BMI indices as outcome measures in this review is relatively narrow and insensitive, especially when studying PA interventions, as PA interventions might have an impact on BMI by affecting intermediate outcomes (increasing PA). We are planning to consider using behavioral outcomes in a future systematic review. Fifth, we only included RCTs in this review, which cannot address complex interplay of behaviors and real-world settings. However, RCTs are the best available approach to answer “can it work?”, as non-randomized trials might result in incomparable baseline data between the two groups, and uncontrolled trials can hardly eliminate the risk of self-selection bias. Sixth, due to the limited number of included studies as well as the limited sub-group data available for meta-analyses, we cannot investigate whether our findings of potentially effective intervention components were influenced by sex, weight status or socio-economic status of the study population. This is thus should be a potential focus for future trials, which provides a basis for the coming meta-analyses.

Despite these limitations, our study, based on a systematical review of the best available evidence from RCTs, took a first step towards distinguishing characteristics of effective school-based obesity prevention interventions. The findings of this review enable a better understanding of the effectiveness of complex school-based obesity prevention interventions. Specifically, the findings of this review suggest that school-based interventions could have significant effects on reducing students’ BMI. The effects of single-component (PA) interventions can be improved when emphasizing students’ enjoyment in physical activity, or including curricular PA sessions.

Overall, school-based interventions are effective in reducing excessive weight gain of children. Findings of this review increase our understandings of potentially effective characteristics of interventions. Future high-quality studies should focus more on the interplay of intervention components, which could deepen our understandings of the complexity of obesity prevention interventions delivered in school settings.

Availability of data and materials

The datasets analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

Body mass index

Confidence interval

Dietary improvement

Health education

Physical activity

Randomized controlled trial

Standard deviation

School policy

Template for intervention description and replication

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Acknowledgments

We thank all the members in our research team.

This work was supported by National Key R&D Program of China (2016YFC1300204), National Natural Science Fund (81703240; 81903343) and Postdoctoral Research Foundation of China (2019 M650391).

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Zheng Liu and Han-Meng Xu contributed equally to this work.

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Department of Maternal and Child Health, School of Public Health, Peking University, Beijing, China

Zheng Liu, Han-Meng Xu, Yuan-Zhou Peng, Li-Zi Lin, Shuang Zhou, Wen-Hao Li & Hai-Jun Wang

School of Public Health, Sydney Medical School, University of Sydney, Sydney, Australia

Li-Ming Wen

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ZL and HMX contributed equally and are considered co-first authors. Study design: HJW and ZL; Study selection: ZL, HMX, YZP and LZL; Data extraction: HMX, ZL; Quality assessment: HMX, ZL; Data analysis: ZL, HMX, LMW, YZP, LZL, SZ, WHL, HJW; Drafting of the manuscript: ZL, HMX, LMW, YZP, LZL, SZ, WHL, HJW; Critical revision of the manuscript for important intellectual content: HJW, LMW. All authors read and approved the final manuscript.

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Additional file 1:.

Table S1. Description of the included trials. Table S2. Description of the characteristics of the PA component for the included studies. Table S3. Description of the characteristics of the DI component for the included studies. Table S4. Differences of overall effect size by sex, weight status and country of the study population. Table S5. Subgroup analyses by characteristics of multi-component interventions (excluding heterogeneous studies). Table S6. Subgroup analyses by characteristics of single-component interventions (excluding trials assessed as high risk of bias). Table S7. Subgroup analyses by characteristics of multi-component interventions (excluding trials assessed as high risk of bias). Table S8. The list of excluded studies. Figure S1. Pooled intervention effect after excluding heterogeneous studies (BMI). Figure S2. Pooled intervention effect after excluding studies at high risk of bias (BMI). Figure S3. Pooled intervention effect after excluding studies at high risk of bias (BMI Z-score).

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Liu, Z., Xu, HM., Wen, LM. et al. A systematic review and meta-analysis of the overall effects of school-based obesity prevention interventions and effect differences by intervention components. Int J Behav Nutr Phys Act 16 , 95 (2019). https://doi.org/10.1186/s12966-019-0848-8

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DOI : https://doi.org/10.1186/s12966-019-0848-8

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The prevention and treatment of childhood obesity 

Through randomised controlled trials, this paper focuses on the effectiveness of interventions in the prevention and treatment of childhood obesity. 

Treatment of Childhood Obesity: A Systematic Review

The purpose of this quantitative systematic review is to provide an update of the evidence, illustrating the efficacy of childhood obesity treatment, considering whether treatment fidelity has been measured and/or reported and whether this related to the treatment effect size. 

Diet, physical activity and behavioural interventions for the treatment of overweight or obese children from the age of 6 to 11 years

The objective of this systematic review was to assess the effects of diet, physical activity and behavioural interventions for the treatment of overweight or obese children aged 6 to 11 years. 

Treatment Interventions for Early Childhood Obesity: A Systematic Review

This systematic review attempted to address the following question: "in childen ag 0-6 years of age who are overweight or obese, what behavioural or clinical interventions have been shown to be effective in reducing adiposity using a clinical trial design?" 

Surgery for the treatment of obesity in children and adolescents

The objective of this systematic review was to assess the effects of surgery for treating obesity in children and adolescents. 

Multicomponent Lifestyle Interventions for Treating Overweight and Obesity in Children and Adolescents: A Systematic Review and Meta-Analyses

The aim of this systematic review was "to assess the effect of multicomponent lifestyle interventions including two or more lifestyle components on change in BMI and BMI z-scores in children and adolescents compared to control conditions of standard, minimal or no treatment."

Interventions for treating obesity in children (Review)

The objective of this review is "to assess the efficacy of a range of interventions designed to treat obesity in children and adolescents, specifically the evaluation of any combination of lifestyle, drug or surgical interventions, compared with any other combination of these interventions or no treatment." 

Diet, physical activity, and behavioural interventions for the treatment of overweight or obesity in preschool children up to the age of 6 years (Review)

The objective of this review was "to assess the effects of diet, physical activity and behavioural interventions for the treatment of overweight or obesity in preschool children up to the age of 6 years." 

Adherence to nutritional therapy in obese adolescents; a review

Given the limited evidence and the existing controversies on the topic, the aim of this review was "to discuss adherence to diet in obese adolescents."

Systematic review of the effectiveness and cost-effectiveness of weight management schemes for the under fives: a short report

The objective of this systematic review was "to search for, review and synthesise studies of the effectiveness and cost-effectiveness of weight management schemes for the under fives."

Weight Loss in Adolescents After Bariatric Surgery: A Systematic Review

The purpose of this article was "to examine existing literature and primarily report weight loss after bariatric surgery, while also describing the effect of bariatric surgery on comorbid conditions and post-operative complications." 

Treatment of Pediatric Obesity: A Systematic Review and Meta-Analysis of Randomized Trials

The aim of this report was "to briefly summarise the findings of a systematic review and meta-analysis of randomised trials published in the literature up to February 2006 and reports on the effects of evaluated treatments on obesity outcomes." 

Lifestyle Interventions in the Treatment of Childhood Overweight: A Meta-Analytic Review of Randomized Controlled Trials

The primary aim of this study was "to use meta-analytic techniques to quantitatively evaluate the efficacy of lifestyle interventions in the treatment of pediatric overweight by comparing lifestyle interventions to waitlist/no treatment control groups or information/education-only control groups." 

Treatment of overweight and obesity in children and youth: a systematic review and meta-analysis

The aim of this review was "to provide an updated synthesis of the evidence on benefits and harms of overweight and obesity treatment interventions for children and adolescents feasible for use in or referral from primary care, and examined the features of efficacious interventions." 

School-based interventions versus family-based interventions in the treatment of childhood obesity - a systematic review

The aim of this review was "to provide up-to-date evidence from research studies, which have employed a study design seeking to compare the outcomes of school-based intervention with family-based intervention in the treatment of childhood obesity."

Diet, physical activity and behavioural interventions for the treatment of overweight or obese adolescents aged 12 to 17 years

The objective of this systematic review was "to assess the effects of diet, physical activity and behavioural interventions for the treatment of overweight or obese adolescents aged 12 to 17 years." 

Parent-only interventions in the treatment of childhood obesity: a systematic review of randomized controlled trials

This systematic review aimed "to add to the current knowledge in this area by including comparisons of parent-only groups with parent-child or child-only intervention groups for children aged 5-12 years." 

The dose of behavioural interventions to prevent and treat childhood obesity: a systematic review and meta-regression

The purpose of this systematic review was "to review the existing literature on behavioural interventions to prevent and treat childhood obesity and to use quantitative methods to better understand how dose was related to outcome."   

The effects of metformin on insulin resistance in overweight or obese children and adolescents: A PRISMA-compliant systematic review and meta-analysis of randomized controlled trials

The present meta-analysis "investigated the efficacy and safety of metformin in improving insulin resistance in overweight or obese children and adolescents, to provide a scientific basis for the application of future clinical evidence." 

Drug interventions for the treatment of obesity in children and adolescents

The objective of this systematic review was to assess the effects of drug interventions for the treatment of obesity in children and adolescents. 

Adolescent bariatric surgery: a systematic review of recommendation documents

This systematic review was conducted "to generate a complete record of all US recommendation documents and describe variability across documents." 

A systematic review of community-based interventions for the treatment of adolescents with overweight and obesity

The aim of this systematic review was "to evaluate the characteristics and effectiveness of scalable community-based secondary prevention and weight-management programs for adolescents (aged 13-17 years) with overweight or obesity."

Treatment of obesity, with a dietary component, and eating disorder risk in children and adolescents: A systematic review with meta-analysis

The aim of this systematic review with meta-analysis was "to assess the impact of obesity treatment, with a dietary component, on the prevalence of eating disorder, eating disorder risk and related symptoms in children and adolescents with overweight or obesity." 

Treating Obesity in Pre-schoolers: A Review and Recommendations for Addressing Critical Gaps

The aim of this review is to identify issues within the treatment of obesity in American pre-schoolers and suggest solutions. 

Impact of mobile apps to combat obesity in children and adolescents: A systematic literature review

The aim of this review is to evaluate “the impact of mobile app technology on obesity‐related anthropometric, psychosocial, and behavioural outcomes in children and adolescents.” 

Exercise and BMI z-score in Overweight and Obese Children and Adolescents: A Systematic Review and Network Meta-Analysis of Randomized Trials  

The purpose of this systematic review was to “Examine the effects of selected types of exercise (aerobic, strength training, [or] both) on BMI z-score in overweight and obese children and adolescents” by using network meta-analysis.

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BioMed Research International

Systematic review of setting-based interventions for preventing childhood obesity.

Introduction . Child obesity is recognized as one of the major public health problems globally, which demands multicomponent and comprehensive interventions. The objective of this systematic review is to evaluate, synthesize, and combine the existing evidence of various setting-based interventions across developed and developing countries that aim to prevent childhood obesity. Methods . An electronic and systematic search was conducted on setting-based interventions related to childhood obesity both in developed and developing countries. A study was considered eligible if it was a randomized controlled trial that focused on home-based, school-based, or community-based intervention for childhood obesity and published in English from 2010 to 2020. A wide range of electronic bibliographic databases, such as PubMed, Medline, Embase, and ERIC were searched. The various studies were carried out among children aged 4-18 years old. A total of 32 studies were identified; out of which 24 were school-based interventions, and the remaining were nonschool-based. Results . The studies in this review highlighted important school and nonschool-based interventions to avoid obesity among children and adolescents. School-based interventions that had considered both physical activity (PA) and diet along with home elements showed great effectiveness. These findings reveal that the specific intervention components such as nutrition education curriculum, prolonged time for PA, and upgrading self-efficacy of study participants should be considered to prevent obesity across developed and developing countries. However, the findings from nonschool-based interventions were restricted by the scarcity of the studies. Conclusion . Multisetting and multipronged strategies are required to avoid or reduce childhood obesity across the globe. However, additional studies are needed with a large sample size. Further study designs based on theory should be conducted in nonschool settings for the creation of meaningful and detailed guidelines that can support the prevention of obesity in children.

1. Introduction

Child obesity is the main public health problem worldwide and has affected more than 155 million children; hence, the World Health Organization (WHO) has recognized childhood obesity to be a significant challenge of the twenty-first century [ 1 ]. The incidence of childhood obesity is quite high among low- and middle-income countries undergoing nutrition and economic transition, where 20-30% of children suffer from this issue [ 2 ]. Globally, around 10% of school-going children carry additional body fat, and 25% of them are categorized as obese children [ 3 ]. Further, according to recent reports, the burden of childhood obesity has risen ten times in the last 40 years owing to changing diets and lack of exercise, which can be considered as major contributors to childhood obesity.

Childhood obesity is multifactorial [ 4 ], encompassing additive and multiplicative interactions between genes and environment that could be reflected in one’s learned behaviour, food consumption, sedentary lifestyle, and sociocultural provocations [ 4 , 5 ]. Such interactions that result in childhood obesity can lead to numerous outcomes such as cancer, cardiovascular diseases, hypertension, and diabetes mellitus later in life [ 6 ]. Considering the financial implications of obesity and its associated comorbidities, prevention approaches are vital, especially in developing nations that ought to manage the double jeopardy of obesity and undernutrition [ 2 ]. Therefore, governments and policymakers need to prioritize this problem by designing cost-effective and sustainable interventions [ 2 ]. However, addressing childhood obesity can be difficult due to its complex nature and multicausality, but different interventions have been tested to address childhood obesity in various studies through randomized controlled trials [ 2 ]. Besides, the existing premise also suggests that there needs to be a focus on early life stages of a child’s development to break the cycle of obesity [ 7 ].

Generally, the evidence demonstrates that childhood obesity can be managed both by pharmacological (medical or surgical) and nonpharmacological interventions [ 8 ]. Nonpharmacological interventions might need to include individual, parent, family, and school-based interventions, thus making them more comprehensive and holistic [ 8 ]. In other words, the latter approach comprises alteration of behavioural factors such as improved physical activity (PA), intake of a healthy and nutritious diet, and altering environmental factors [ 8 ]. However, interventions have mostly focused on the individual level, thus ignoring the “obesogenic environment,” which is the sum of the effects that surrounding circumstances have on fostering obesity among children [ 9 ]. Altering the “obesogenic” environment could generate a more long-lasting impact on the behaviour of a child [ 10 ]. For instance, children intermingle with microenvironments including schools, homes, and neighbourhoods [ 9 , 10 ]. These microlevel environments are affected by the wider macroenvironments including government policies, education and health systems, and the food industry, which are less modifiable.

Furthermore, parents play a vital role as a mediator to shape the behaviour of their children, since children spend most of the time at homes [ 11 ]. Likewise, learning settings, such as schools offer a platform to adopt a healthy lifestyle via health education and health promotion strategies throughout critical stages of child growth and development [ 9 ]. Thus, this setting-based (home, school, and community-based) interventions seem to play a crucial role to prevent or eliminate childhood obesity [ 9 ]. Despite the previous interventions that have been evaluated by many randomized controlled trials, findings of such studies are not reviewed and synthesized collectively. Therefore, it is essential to collectively assess and evaluate the effectiveness and outcomes of these interventions to give robust evidence for preventing and managing childhood obesity.

2. Material and Methods

The objective of this systematic review was to evaluate, synthesize, and combine the existing evidence on setting-based interventions related to childhood obesity. Guidelines specified by Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) were used to carry out this systematic review [ 12 ].

2.1. Inclusion and Exclusion Criteria

We carried out an electronic and systematic search in the literature review on setting-based interventions related to childhood obesity both in developed and developing countries across the world. To answer the study question, the eligibility of a study was contingent for inclusion if it was a randomized controlled trial (RCT) that was focused on nonpharmacological interventions for childhood obesity including home-based, school-based, or community-based intervention, an original research study published in English from 2010 to 2020. More specifically, we included those studies that were aimed at avoiding or controlling weight gain among children and adolescents (aged 2–19 years) in the settings such as school, preschool, community, and home by either focusing on a nutritional plan or PA or both. On the contrary, any study that had included pharmacological intervention and was published before 2007 was excluded from the review. In addition, we also excluded secondary data, letters to the editor, case reports, and grey literature from this systematic review. We grouped the eligibility criteria into four major categories using the PICOS (population, intervention, outcome, and settings) framework as given in Table 1 .

2.2. Information Sources and Search Strategy

We started and completed a systematic search of published articles in 2020. A wide range of electronic bibliographic databases such as PubMed, Medline, Embase, and ERIC was searched. We also explored references of pertinent reviews along with the database search. The primary outcome of the analysis was a reduction in childhood obesity that was mainly assessed by the prevalence of obesity at the end line. This was evaluated by the change in factors including body mass index (BMI), waist circumference, body fat percentage, and skinfold thickness from starting to the end of the study. We also grouped into four major categories of the same PICOS (population, intervention, outcome, and settings) framework. We prepiloted the search strategies without any restrictions by year of publication, geographic area or country, or other sociodemographic characteristics.

We labeled a study with favorable or positive findings if all outcomes of particular interest in the intervention arm demonstrated a statistically significant decline in adiposity. On the other hand, we classified a study with mixed results if more than one of the outcomes such as BMI, waist circumference, and skinfold thickness in the intervention group revealed a positive effect. The study was labeled to have negative findings when all the outcomes in the intervention group upsurged significantly, and lastly, we considered a study with no effect on the outcome when there were no significant differences found between the intervention and controlled group for the particular outcome.

We identified a combination of Medical Subject Heading (MeSH) keywords and text words. These were also clustered into four major groups based on the categories of population, intervention, outcome, and settings. The most prevalent search key terms found in abstracts and titles comprised of “setting based interventions for childhood obesity,” “childhood obesity AND school-based intervention,” “childhood obesity AND home-based intervention,” “childhood obesity AND community-based intervention,” “intervention for childhood obesity,” and “sustainable interventions for childhood obesity.” Further, we consulted with a librarian to generate a search in four different parts. The first part was restricted to search terms specific to the primary outcome such as “overweight/obese”; the second part was for the terms limited to the population of the study including “children” and “pediatric”; the third part was related to the terminology relevant for the intervention such as “prevention” and “control”; and the last term was related to the setting including “Preschool” or “home-based.”

Besides, we also considered using diverse wordings of main concepts such as childhood obesity vs. obesity among children to obtain pertinent research papers. This was followed by combining these major concepts using combinations (AND, OR) relevant to the research question. Moreover, to detect more research articles, we also used truncation ( ) with the same root word. While executing the search strategy, a filter was applied to retrieve articles in English language only. Additionally, restrictions were applied on publication period, age group, and type of studies to include eligible studies in our systematic review.

2.3. Data Abstraction

We imported all appropriate research studies into the reference manager software (Endnote™) file. Titles were screened for duplicates in this software. We did not consider the abstracts for further review, which did not explicitly explore the study objective. Finally, we obtained and examined the full-text articles of the remaining relevant articles. This was followed by abstracting and summarizing the articles that met the eligibility criteria using a standardized proforma. Thus, after the process of removing duplicates, title, and abstract screening, we removed papers that were beyond the scope of this review as guided by inclusion criteria. Besides, the bibliography of the remaining studies was also checked and scrutinized to evade missing any useful studies. This process of searching the articles was carried out independently by the reviewers, and their judgments and extracted summaries were matched to identify the differences and resolve these accordingly.

Independent reviewers filled a standardized data extraction sheet for eligible research articles. The reviewers compared the data extraction tables to ensure including the imperative findings of the eligible studies and pilot tested the data extraction sheet before starting the process of data extraction. Besides, prevailing research articles on the chosen topic were reviewed to describe objects of the data extraction proforma. Any discrepancies between the two reviewers were resolved by discussion and agreement. The abstracted data comprised the author, reference, publication year, and title; total sample size; sample size by gender if applicable; medical field, a method to measure outcome; factors of satisfaction and factors of dissatisfaction; and ranking of the included medical faculty members.

3.1. Findings of the Search Strategy

We screened the identified articles initially by titles and then by abstracts, and finally, we carried out full-text article assessment. Articles that did not meet the eligibility criteria were not included. As a result, our initial search identified 5,250 citations in different databases; however, 2,505 articles were duplicates that were removed. Of the remaining 2,745 unique studies, we reviewed titles and abstracts and found 1,525 relevant abstracts. Upon reviewing abstracts, 1,190 articles did not meet the eligibility criteria while reviewing the abstracts, and 303 did not meet eligibility after reviewing full texts. Hence, we were able to retrieve full texts for 32 articles, which were included in the review as shown in Figure 1 .

systematic review child obesity

3.2. Characteristics of the Eligible Studies

With respect to the setting, of these thirty-two studies, twenty-four were undertaken in the school settings, and eight were done in nonschool setting, of which five were done in the preschool setting, 1 was conducted in the community, and only two were carried out in the home. Regarding the effect of the intervention on the outcome, seven studies revealed a favourable effect on the outcome with positive findings, twelve studies had combined results with mixed effects on the outcomes, and thirteen studies did not find any difference between the intervention and controlled arm. Positive results mean the given intervention resulted in the reduction of all obesity-related outcomes such as BMI, skinfold thickness or waist circumference, percentage of body fat, and prevalence of obesity in the intervention group. On the other hand, negative effects mean that the reduction in these outcomes was noticed in the control group rather than the intervention group. Lastly, mixed-effects mean that not all obesity-related outcomes were improved in the intervention group; rather, it implies that at least one of these outcomes improved. Details of the type of intervention, length of intervention, length of follow-up, age groups of children involved in the intervention, outcome of the intervention, and effect of the intervention on the outcome are presented as shown in Table 2 .

3.3. Findings of the School-Based Interventions

Overall, 24 RCTs were evaluated interventions to control weight gain in school settings [ 13 – 36 ]. Generally, the results of the school-based RCTs were diverse with most studies revealing positive or combined findings [ 14 , 15 , 17 – 23 , 25 – 30 , 33 ], and several studies demonstrated no difference between intervention and control group. Almost all RCTs that reported statistically significant findings used both PA and dietary interventions [ 18 , 19 , 21 , 32 ]. More specifically, the intervention components included an education curriculum for nutrition, a prolonged time for PA [ 18 , 19 , 21 ], and upgrading self-efficacy of study participants [ 18 , 20 ]. On the contrary, almost 50% of RCTs conducted in school-based settings with no significant findings utilized mixed interventions of PA and diet [ 16 , 32 , 35 , 36 ] and the rest of the studies focused entirely on diet, PA, or chasing body measurement [ 13 , 31 , 34 ]. These studies showing insignificant findings also emphasized supplementary approaches implemented in the respective RCTs such as changes at the policy level social marketing, and communication about the health status of study participants [ 16 , 34 – 36 ]. Most RCTs with combined findings used a combination of PA and interventions [ 13 – 15 , 17 , 22 , 25 , 27 , 30 ] such as education curriculum [ 14 , 15 , 17 , 22 – 25 , 27 – 30 ] or prolonged PA time [ 15 , 22 , 24 – 29 , 33 ], and environmental changes [ 14 , 22 ].

In numerous RCTs with insignificant findings, the interventions were offered for short period and the follow-up time ranged from 5 weeks to 7 years [ 16 , 32 – 35 ]. With respect to the outcome, the studies with statistically significant findings reported only BMI or its - score as a unique primary outcome. In contrast, the studies with insignificant results reported a range of outcomes such as waist circumference [ 13 , 17 , 25 , 26 , 28 , 30 ], skinfold thickness [ 33 ], body fat percentage [ 13 , 23 , 24 , 26 ], and incidence of overweight or obesity in addition to the BMI [ 14 , 22 , 23 , 26 , 28 , 30 , 32 , 34 , 35 ]. Most of the RCTs with insignificant findings considered children as well as adolescents and were conducted in countries such as China, Argentina, Australia, Spain, and Denmark [ 13 , 16 , 31 , 34 , 35 ]. Around 50% of the RCTs showed combined findings, and intervention effect was based on factors such as duration of follow-up [ 17 , 24 , 33 ], type of intervention [ 14 , 15 ], and the outcome of interest [ 17 , 22 , 24 – 30 ] or inclusion of extraneous factors in the final model [ 23 ].

3.4. Findings for the Nonschool-Based Interventions

3.4.1. childcare and preschool-based interventions.

Overall, five RCTs tested the proposed interventions to manage weight gain in preschool settings [ 37 – 41 ], and findings of the RCTs had a wide range of positive [ 37 – 39 ] and insignificant findings [ 40 , 41 ]. The duration of follow-up varied between 9 months [ 37 , 38 ] to 2 years [ 39 ]. The majority of RCTs in childcare settings documented favourable findings that emphasized PA [ 37 , 38 ] entirely except for one study that advocated a multipronged approach by including environmental interventions at the policy level at childcare settings [ 39 ]. The intervention focused on both healthy diet and PA policies. These policies promoted a healthy drink intake among school staff and children, focusing on water as the main beverage and limiting juice intake to once per week. The intervention also focused on a daily intake of fresh fruits and/or vegetables, encouraged PA for >60 min/d, and reduced screen time limited to <30 min/week [ 39 ]. This study noted a significant increase in the nutritional consumption of fruit and vegetable of obese children in the intervention group compared to the control group [ 39 ]. These second RCTs that had favourable findings were carried out in USA, considered BMI as the main outcome, and included children from low-income families. The interventions included cognitive-behaviourally based PA that was conducted among 4-5-year-old children. Age-appropriate cognitive-behavioural techniques related to PA were tested in these RCTs and were carried out in the USA. The interventions were associated with a significantly greater percentage of moderate-to-vigorous and vigorous PA in a preschool day. The intervention was also associated with a significant reduction in BMI, with effect sizes greatest in overweight and obese children [ 37 ]. In contrast, the RCTs with no difference between intervention and control group ( ) delivered a two-week education program focusing on a nutritious diet and PA [ 40 , 41 ]. However, one study also added family-centred intervention by arranging classes for parents on a nutritious diet and PA [ 40 ].

3.4.2. Community and Home-Based Interventions

Several community and home-based RCTs were carried out in the USA by trained staff and involved families with children through partnering with different community settings. One RCT was conducted in the community setting in the USA where public recreation centres were randomly allocated to a health-promoting intervention that focused on exercise-centre policies, PA programs, and services while incorporating family-centred approaches including visits at home and group workshops [ 42 ]. The BMI, diet, and PA for each child were monitored from baselines to 2-year postbaseline. After following the participants, there were no significant difference found in the outcome between the two groups ( ) among children aged 5 to 8 years.

Two home-based RCTs conducted in the USA [ 43 , 44 ] evaluated interventions to manage weight gain, both of which did not find any difference between the intervention and treatment groups, although both RCTs were executed in community centres and was directed towards families. For instance, one RCT involved 160 families with children aged 8-12 years that were randomly allocated to an intervention that focused on their nutritional education and meal planning and encouraged to reduce screen time while having meals [ 43 ]. The researchers did not find any significant difference in the outcome between intervention and control group after 12 months ( ) or at the end of 21 months ( ).

4. Discussion

We reviewed 32 RCTs with diverse interventions that were tested around the world in this systematic review. The initiatives were intended to reduce or control weight gain in children and teenagers, with the most of the RCTs ( ) predominantly carried out in the school setting. The majority of the studies ( ) found statistically significant and favourable results of the respective interventions for at least one obesity-related outcome among school-based studies. These results reveal that schools should be considered as focal points for interventions to prevent childhood obesity [ 45 , 46 ]. Students devote 50% of their time and eat at least one-third of their everyday calories at school, and current facilities can be used by educational institutions to prevent obesity without major alterations to the timetable or lifestyle of the child [ 46 ].

A blended diet and PA approach were implemented by most of the school-based RCTs, which showed a positive or mixed result. This is analogous to previous evidence that indicates that a mixed approach to diet and PA may be more effective compared to a single strategy [ 47 ]. With an emphasis on the strength of action, the benefit of integrated approaches over single methods should be further discussed. An additional home setting was also included in most school-based RCTs in which the results of the intervention were found to be beneficial; this finding is in concordance with existing evidence that acknowledges the role of the family members and home setting in affecting the children and adolescents’ health behaviour [ 48 , 49 ].

One possible reason that several studies did not seem to be able to identify alterations in the outcomes related to obesity may partly explain studies with combined findings. In this systematic review, over half of the studies did not have a well-defined primary outcome. Among the RCTs with combined findings for which a primary outcome was established, 9 RCTs found that the intervention had a statistically significant positive effect. Results from RCTs conducted in nonschool environments have been less coherent. This is because there have been somewhat fewer programs, completed in nonschool settings, with six studies in preschool settings. In general, in both PA-only and mixed diet and PA approaches, the best preschool trials showed modest proof of efficacy. All the preschool-based studies were carried out in low-income nations that focused on minority groups. While there were only two RCTs performed solely in the home, most school-based studies with favourable outcomes reported for intervention in a secondary home environment. The value of the home setting should not be overlooked based on the minimal data available. Future studies are needed to test the interventions addressing different contexts (e.g., school and home) to help control childhood obesity.

Regarding the duration of treatments, it should be noted that some studies included intervention components that have altered the policy, environment, or personnel education, which may have had repercussions that have continued beyond completion of assessments. Such interventions might continue beyond the study period, and it is worth assessing the sustainability of such programs. This is because, apart from the short-term or medium-term efficacy of the RCTs, the viability of initiatives must be addressed. In addition, helping children sustain healthy habits after the study is over to avoid gain in weight is important. Furthermore, policy and environmental changes that eliminate barriers to modifying individual behaviours will help change the obesogenic circumstances that lead to increased weight [ 50 ].

4.1. Strengths and Limitations

Our review has unique strengths. First, we included RCTs to have meaningful and valid estimates for the outcomes. Second, we carried out a comprehensive review of obesity-related intervention by incorporating both school and nonschool settings. Third, we included studies from both developing and developed countries to assess the efficacy of interventions that have been implemented across diverse settings. However, the study results need to be interpreted considering few limitations. First, the included RCTs had variation in the study parameters such as length of follow-up, type of outcome, and several study participants that rendered difficult for a researcher to compare the findings across various studies. Second, we limited our review to studies that were published in the English language, and studies published in a non-English language might have different findings than we noticed, thereby introducing publication bias.

5. Conclusion

The findings of the review indicate reasonable evidence to endorse school-based approaches that incorporate components of both diet and PA and as well as a home environment to minimize childhood obesity. However, further research is required with strong study designs that are based on theory and carried out in nonschool settings for the creation of meaningful and detailed guidelines that can support the prevention of obesity in children. Multisetting and multipronged strategies are required for the most positive outcomes to avoid or reduce childhood obesity across the globe. Since most of the evidence with favourable findings was coming from developed countries, therefore, specific attention to implementing future studies in developing countries is warranted. This systematic review has important policy implications to reduce obesity among children both in developed and developing countries. The environment in all settings such as schools, preschools, and communities need to be conducive in a way that should not encourage children to adapt obesogenic environment. This means that schools in developed countries should have meal plans with nutritious diets and a physical environment for doing physical activity. Activities such as sports should be encouraged in schools with enough time scheduled for different types of physical activities. A school curriculum should be adapted which students are taught about the importance of being active and consuming a healthy diet. These cost-effective interventions are also applicable in the developing countries; however, such countries might need more cost-effective interventions such as physical activity in the form of walking for 30 minutes each day. Additionally, developing countries also need to integrate some modules of improving physical activity and avoiding unhealthy diets in their existing curriculum. More macrolevel actions are required at the policy level to avoid selling unhealthy foods to children and adolescents. Moreover, governments should focus on building local parks and playgrounds in neighbourhoods to keep children physically active and engaged.

Data Availability

The data supporting this systematic review are from previously reported studies and datasets, which have been cited within the manuscript. The processed data are freely available online.

Ethical Approval

Ethical approval is not necessary.

Consent is not necessary.

Conflicts of Interest

The authors declare that they have no conflicts of interest..

Authors’ Contributions

Both authors contributed to the writing of the manuscript.

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Added value of this study, implications of all the available evidence, introduction.

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Research Article

Interventions for obesity among schoolchildren: A systematic review and meta-analyses

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Validation, Writing – review & editing

Affiliation Unit of Sports Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, Wilayah Persekutuan, Malaysia

Roles Data curation, Formal analysis, Investigation, Methodology, Project administration, Software, Validation, Writing – original draft

* E-mail: [email protected]

Affiliation Department of Family Medicine, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Selangor, Malaysia

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Fig 1

Childhood overweight and obesity has emerged as a major public health threat worldwide with challenges in its management. This review assessed the effectiveness of interventions for childhood overweight and obesity.

A systematic literature search was conducted using CINAHL, EMBASE, Ovid MEDLINE, PsycINFO and SPORTDiscus databases to retrieve articles published from 1st January 2000 to 31 st December 2017. Randomised controlled trials (RCTs) and quasi-experimental studies comparing different strategies in managing overweight and obesity among schoolchildren (6 to 12 years of age) were included. The main outcomes of interest were reductions in weight related variables included anthropometry and body composition measurements. All variables were analysed using random effects meta-analyses.

Fourteen studies were reviewed, 13 were RCTs and one was a quasi-experimental study. The risk of bias for randomisation was low risk for all of RCTs except for one, which was unclear. The risk of bias for randomisation was high for the quasi-experimental study. Most interventions incorporated lifestyle changes and behavioural strategies such as coping and problem solving skills with family involvement. The meta-analyses did not show significant effects of the intervention in reducing weight related outcomes when compared with controls.

Meta-analyses of the selected studies did not show significant effects of the interventions on weight related outcomes among overweight and obese schoolchildren when compared with controls. The role of interdisciplinary team approaches with family involvement using behaviour and lifestyle strategies to curb obesity among schoolchildren is important.

Citation: A. Hamid MS, Sazlina SG (2019) Interventions for obesity among schoolchildren: A systematic review and meta-analyses. PLoS ONE 14(1): e0209746. https://doi.org/10.1371/journal.pone.0209746

Editor: Shahrad Taheri, Weill Cornell Medical College in Qatar, QATAR

Received: April 24, 2018; Accepted: December 11, 2018; Published: January 9, 2019

Copyright: © 2019 A. Hamid, Sazlina. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper.

Funding: We would like to thank Universiti Putra Malaysia for their support in conducting this review.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Childhood overweight and obesity is a serious public health problem worldwide in the 21 st century. The prevalence of overweight and obesity has increased in almost all countries worldwide especially in economically developed countries [ 1 – 3 ].

The traditional perception that a heavy child is a healthy child has changed based on evidence that overweight and obesity in childhood is associated with a wide range of serious health complications [ 4 ]. Overweight and obese children are more likely to have cardiovascular (e.g. hypertension, heart disease, high cholesterol), metabolic (e.g. type 2 diabetes), and psychosocial illnesses (e.g. eating disorders, depression and low self-esteem) than their normal-weight counterparts [ 1 ]. Also, children who were overweight and obese are at greater risk of premature illness and death in later life [ 5 ].

The United Nations International Children’s Emergency Fund (UNICEF) defined overweight and obesity as excessive and unbalanced nutrition to a point at which health is adversely affected [ 6 ]. The aetiology and pathogenesis of overweight and obesity often involve complex interaction between genetic makeup and environmental factors. Adoption of sedentary behaviour (physical inactivity, watching television and sitting in front of computer) combined with excess caloric consumption are examples of the environmental factors that are potentially modifiable in the battle against overweight and obesity [ 7 , 8 ].

While the fundamental principles of weight management in children might seems straightforward through reduction in energy intake and increase energy expenditure, the results of current intervention studies on childhood overweight and obesity prevention are variable. A systematic review and meta-analyses on the management of obesity among children less than 18 years of age concluded that lifestyle interventions may lead to improvements in weight and cardio-metabolic outcomes [ 9 ]. However, the evidence is limited on the optimal duration of the intervention and its long-term effectiveness. A more recent review conducted in 2015 that focused only on pre-school childhood obesity (<6 years of age) found multidisciplinary and intensive interventions have some evidence of efficacy in reducing body fat and fat mass [ 10 ]. Therefore, the objective of this review was to examine the effectiveness of interventions (including dietary, physical activity and behavioural interventions) in reducing weight related outcomes among overweight and obese children 6 to 12 years of age. It is hoped that the results from this review would provide information and guide medical practitioners and health policymakers on the management of childhood overweight and obesity.

Materials and methods

A systematic review was conducted to explore the current approaches on managing overweight and obesity among schoolchildren. The review question was: How effective are current intervention(s) in reducing weight related outcomes including anthropometry and body composition among overweight or obese schoolchildren?” This review was registered with the International prospective register of systematic reviews (PROSPERO) CRD42016037918 [ https://www.crd.york.ac.uk/prospero ].

Study selection

The study design considered in this review included randomised controlled trials (RCTs) and quasi-experimental studies. We included studies that compared strategies on the management of overweight and obesity among schoolchildren aged between 6 and 12 years of age to usual care or minimal advice. Overweight or obese were defined based on several criteria, including BMI z-scores (or standard deviation (SD) scores) [ 11 ], BMI percentile [ 12 ], BMI cut-offs based on age and gender [ 13 ] and percentage of weight for height [ 14 ]. However, studies that classified overweight or obese using other definitions were also considered. The primary outcome of this review was a change in weight related outcomes, which included anthropometry (including weight, standard body mass index (BMI) in kg/m 2 , BMI percentile, BMI z-scores and standard deviation scores, percent of overweight, weight for height percentage, waist circumference) and body composition (including lean body mass, body fat and fat mass).

The secondary outcomes measured were changes in physical activity and dietary behaviour. Physical activity assessed using physical activity questionnaires, and/or activity monitors (such as accelerometer and pedometer) as well as assessment of sedentary activities were considered in this review. Studies reporting changes in dietary intake including carbohydrate and fat intake as well as caloric estimates were included. We excluded studies that focused on interventions for preschool age groups or adolescent, interventions on prevention of obesity, on drug treatment of obesity or on normal weight children.

Studies that included school-based or non-school based (home, clinic or community) interventions were reviewed. Interventions could include one or a combination of: (1) one-to-one or group counselling or advice, (2) self-directed or prescribed physical activity programmes (with or without supervisions), (3) dietary intervention or 4) behavioural strategies. Interventions delivered by one or more providers (healthcare providers, exercise professionals, or dietitians) were considered. There was no restriction on the type and content of the control group. Interventions could be compared with usual care (no active intervention), participants listed on waiting list or those who received minimal advice.

Data sources & search strategy

Studies were electronically searched using EBSCOhost interface for Medline, CINAHL, Psychology and Behavioural Sciences Collection and SPORTDiscus, and EMBASE databases. We adhered to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines [ 15 ]. The search strategy performed using the Medical Subject Heading (MeSH) terms and keywords. For children, search was done using the MeSH term child and the keywords child$ OR children. For overweight we used a combination of MeSH terms as follows: overweight OR obesity OR pediatric obesity. Diet [MeSH] OR diet, food and nutrition [MeSH] were used for diet and exercise [MeSH] OR physical activity for exercise and behavior therapy [MeSH]. For anthropometry we used body mass index [MeSH] OR body composition [MeSH] OR anthropometry [MeSH].

Peer-reviewed published articles between 1st January 2000 and 31 st December 2017 were used. Published systematic reviews on the management of obesity among schoolchildren were used as the source of randomised controlled trials (RCTs). Potential eligible studies were hand searched from the reference lists of review articles and included studies. We limited the search to include studies that involved children between 6 and 12 years of age. All the titles, abstracts, and full-text of each study retrieved from the search were screened by both reviewers using a standardized form for study eligibility. In cases where there was any doubt on the paper eligibility, the issue was resolved through discussion until a consensus was reached. In view of limited resources for translation, articles that were published in the English language were considered in this review.

Data extraction

The titles and abstracts of all studies retrieved were reviewed following the criteria for study selection to decide if the full-text manuscripts were required for further evaluation. Each full-text article retrieved was evaluated systematically according to the study’s: (1) objective (on the effectiveness of interventions), (2) characteristics of the study (study design, participants’ age, behavioural theoretical model, and sample size), (3) contents of the intervention (intervention strategies, intervention provider, length of intervention and follow-up contacts), (4) targeted outcome/s and (5) major findings.

Methodological quality assessment of individual studies

Each selected study was evaluated for its methodological quality using the Cochrane Collaboration tool for assessing the risk of bias (the Cochrane Handbook for Systematic Review of Interventions) [ 16 ]. It covers: a) sequence generation b) allocation concealment c) blinding d) incomplete outcome data (e.g. dropouts and withdrawals) e) selective outcome reporting and f) other areas of bias. For each domain in the tool, the procedures undertaken for each study were described. Each study was rated as ‘high’, ‘low’ or ‘unclear’ risk of bias based on a judgement of the gathered information. These judgements were made independently by two review authors based on the predetermined criteria and later discussed in a meeting until a consensus achieved.

Data synthesis and analyses

We conducted a narrative synthesis based on the primary and secondary outcomes of this review. The primary outcome measures were pooled and calculated using the statistical software RevMan 5.3, according to the Cochrane Handbook for Systematic Reviews of Interventions [ 16 ]. Attempts to contact the authors to obtain the raw data for data analysis was made but to no avail. The results of the BMI z-score, waist circumference and body fat percentage were analysed using weighted or standardized mean differences as a measure of effect size, with 95% confidence intervals. Since the participant demographics and clinical settings differed among studies, we assumed the presence of heterogeneity a priori. Therefore, we used a random-effects model to pool the results. We assessed heterogeneity using the Cochran’s Q statistic of heterogeneity with reported p-value and the degree of inconsistency across studies was quantified using I 2 . In studies with three arm RCTs, each of the intervention group was analysed independently and compared with the control group. A funnel plot was performed to determine the presence of potential publication bias using the statistical software RevMan 5.3.

Literature search

Three hundreds and two articles were identified through the five databases and cross referencing. Twenty were removed due to duplication. After screening the titles and abstracts, 69 full-text articles were retrieved and assessed for eligibility. Fifty-five articles were excluded because they did not fulfil the selection criteria. The reasons for exclusion included participants age were not between 6 and 12 years of age (n = 35), studies identified were neither RCT nor quasi (n = 13), the comparison group was with normal weight children (n = 1), intervention focused on diabetes prevention (n = 1), not an original research article (n = 2), not in English language (n = 1), and data presented was on cost-analysis (n = 1). A total of 14 articles were included in the narrative synthesis and eight were included in the meta-analyses. The flow diagram for the study selection is described in Fig 1 .

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https://doi.org/10.1371/journal.pone.0209746.g001

Characteristics of selected studies

Table 1 summarises the characteristics of the selected studies. Thirteen RCTs [ 17 – 29 ] and one three-arm quasi-experimental study were reviewed [ 30 ]. Three RCTs were conducted in North America [ 17 , 22 , 25 ], three in Israel [ 27 , 28 , 30 ], the remaining studies were conducted in Netherlands [ 18 ], Norway [ 25 ], Finland [ 21 ], New Zealand [ 23 ], United Kingdom [ 29 ], Australia [ 20 ] and Malaysia [ 24 ]. As for the study setting, three studies were conducted in the community [ 27 – 29 ], five in the hospitals [ 18 – 20 , 26 , 30 ], and three in the clinics [ 17 , 24 , 25 ], of which two were in academic research clinics [ 17 , 24 ]. Two studies were home-based [ 22 , 23 ], and another was conducted in school [ 21 ].

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https://doi.org/10.1371/journal.pone.0209746.t001

Five studies recruited children who were overweight or obese [ 17 , 18 , 22 , 23 , 25 ], while nine recruited only obese children [ 19 – 21 , 24 , 26 – 30 ]. All studies except one excluded participants with comorbidities [ 25 ]. Most studies used BMI percentile to classify overweight or obese [ 17 , 19 , 22 , 24 , 25 , 27 – 30 ]. Three studies used BMI z-scores [ 18 , 20 , 26 ], one used weight for height percentage [ 21 ] and one used the International Obesity Task Force cut points [ 23 ] to classify overweight or obese. Interestingly, the definition used to classify overweight and obese differs in the included studies despite using the same measures. For example, some studies defined obese as BMI percentile >94 th centile [ 22 , 28 , 30 ] while others as BMI percentile >98 th centile [ 27 , 29 ].

All studies had interventions that integrated interdisciplinary approaches involving parent or family. Selected studies incorporated either a combination of behavioural strategies, physical activity, and dietary component [ 17 – 19 , 21 , 24 , 25 , 29 ], behavioural strategies and physical activity [ 22 , 23 ] or physical activity and dietary component without behavioural strategies [ 20 , 26 – 28 , 30 ]. All interventions were delivered by a group of healthcare providers (psychologist, dietitian/nutritionist, physical/sport therapist) except in one study where the intervention was delivered by a clinical psychology graduate student [ 17 ]. One study used short message services [ 18 ], while another used an automated interactive voice response system [ 25 ] to maintain behavioural change. Only five studies incorporated health behavioural theories in their interventions, namely social learning and cognitive theory [ 29 ] alone or combined with behavioural theories or models [ 18 , 23 ], social ecological theory [ 25 ] or the trans-theoretical model [ 30 ]. The duration of intervention varied between 8 weeks and 12 months. In nine studies participants and their families were followed up for 12 to 24 months [ 17 – 21 , 25 , 26 , 29 , 30 ]. Six RCTs were compared with usual care or wait-listed groups [ 17 , 19 , 20 , 23 , 24 , 29 ] while the others were compared with groups that received minimal advice.

All studies assessed weight related measurements as their primary outcomes. Seven studies used BMI z-scores [ 17 , 18 , 20 , 23 – 26 ] and two studies included standard BMI (kg/m 2 ) [ 17 , 22 ] as their primary outcomes. Other studies also included body fat [ 26 ], percentage of overweight [ 17 , 19 ] and weight for height percentage [ 21 ] as their primary outcomes. Six studies measured body composition such as body fat, fat mass and lean body mass as their outcomes [ 19 , 23 , 26 – 29 ]. Five studies measured waist circumference as their outcome [ 19 , 20 , 23 , 29 , 30 ]. One study measured skinfold thickness as their outcome [ 27 ]. However, 11 studies presented more than one weight related outcomes as their outcome measures [ 17 , 19 – 21 , 23 , 24 , 26 – 30 ].

Eight studies measured changes in physical activity and sedentary behaviour including screen time [ 17 , 22 – 25 , 27 – 29 ]. In three studies, the level of physical activity was measured using the accelerometers [ 17 , 22 , 24 ]. Seven studies measured changes in dietary intake including consumptions of unhealthy snacks as outcomes [ 17 , 18 , 22 , 23 , 25 , 26 , 28 ].

Study quality

The risk of bias for randomisation was unclear and low for all 13 RCTs [ 17 – 29 ]. The risk of bias for randomisation among quasi-experimental studies was high as expected. The quasi-experimental study stated random assignment of participants in their interventions. However, details on the randomisation technique was not elaborated [ 30 ].The allocation concealment was described in six (43%) studies [ 18 , 20 – 24 ]. Blinding of participant and personnel was lacking in all studies as anticipated because of the nature of the interventions. In addressing detection bias, blinding of outcome assessment was unclear in most studies. In three studies the outcome measures were performed by assessors blinded to participants’ grouping [ 20 , 22 , 24 ]. The risk for incomplete outcome data was low for all studies except for one [ 29 ]. Sacher et. al (2010) declared loss to follow-up among their participants but did not apply intention to treat analysis [ 29 ]. The proportion of studies with low, unclear and high risk of bias is presented in Fig 2 .

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Effect of interventions compared with controls

Five studies that incorporated behavioural strategies with exercise and dietary interventions reported positive effects on the weight related outcomes [ 17 , 19 , 21 , 25 , 29 ]. Other studies that included behavioural skills and exercise alone [ 22 ] or combination of exercise and dietary interventions [ 27 , 28 , 30 ] also reported positive effects on the weight related outcomes. Of the seven RCTs that measured BMI z-score, four showed significant reductions among participants in the intervention compared to controls [ 17 , 21 , 25 , 29 ]. Three of these studies showed reductions at 6-months follow up [ 17 , 25 , 29 ], of which two studies delivered their interventions in groups sessions [ 25 , 29 ]. Two studies that incorporated family group sessions of behavioural strategies with exercise and dietary interventions showed no reductions in the BMI z-scores when compared to control groups [ 18 , 24 ]. One of these RCTs used SMS to encourage self-monitoring and provided personalised feedback [ 18 ]. Two RCTs that measured BMI percentile also showed reductions at post-intervention when compared to their controls [ 27 , 28 ]. Both studies incorporated group-based diet and physical activity programs with family engagement. The quasi experimental study found dietary intervention alone or combined with physical activities leads to significant reductions in BMI z-scores compared to exercise intervention alone [ 30 ].

Four out of eight RCTs showed increased physical activity in the intervention group compared to the control [ 22 , 27 – 29 ]. One study also showed reduction in sedentary activity among participants in the intervention group. The change was sustained at 6-months follow-up [ 29 ]. Seven RCTs measured dietary intake behaviour as their outcomes, which included carbohydrate and fat intake as well as estimation of caloric intake [ 13 – 16 , 18 , 19 ]. Only two studies showed significant reductions in dietary or caloric intake when compared to the control groups at post-intervention, however, they did not follow up the participants [ 22 , 23 ]. One study showed reductions in fat and caloric intake from snacks and reduction in snack intake during watching television [ 22 ].

All community-based intervention studies reported positive effects on changes of BMI z-score, BMI percentile, waist circumference and/or skinfolds, as well as improvement in sedentary behaviours [ 27 – 29 ]. However, only one study followed participants up to 12 months and showed sustained effects on these outcomes [ 29 ]. One of the three hospital-based studies [ 29 ], one of the two home-based [ 22 ], and each of the clinic-based [ 17 ] and school-based [ 21 ] interventions reported positive effects on the outcomes.

We performed meta-analyses to determine the effect of interventions on changes in BMI z-score, waist circumference and body fat percentage based on different intervention strategies. Some of the selected studies varied in their primary outcomes, therefore, data from studies with similar outcomes were pooled and analysed. Data from eight RCTs (n = 969 participants) were pooled to determine the effects of intervention strategies on the changes of BMI z-scores. However, two of the studies were 3-arm RCTs, which we analysed each intervention separately. No statistically significant difference was found between intervention and controls (standardised mean difference = - 0.14; 95% CI = - 0.87, 0.60; p = 0.72) (see Fig 3 ) [ 17 , 18 , 20 , 23 – 26 , 29 ]. A meta-analyses on three RCTs (n = 434 participants) did not show significant positive effects of any intervention strategies on the changes of waist circumference compared to controls (standardised mean difference = -0.25; 95% CI = -0.51, 0.01; p = 0.06) (see Fig 4 ) [ 20 , 23 , 29 ]. Five RCTs (n = 463 participants) pooled data showed no significant difference in the changes of body fat percentage between intervention and control (standardised mean difference = 0.30; 95% CI = - 0.17, 0.76; p = 0.21) (see Fig 5 ) [ 23 , 26 – 29 ].

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We only present a funnel plot for the BMI z-score outcome but not for the BMI percentile and body fat percentage. This is because a funnel plot with fewer than 10 studies in a meta-analysis would lead to low power of analysis to distinguish the chance from real asymmetry [ 31 ]. Fig 6 depicts the funnel plot for the meta-analysis on the effects of the intervention on the changes in BMI z-score of the selected studies in our review. There was an asymmetry of the plot to suggest presence of publication bias.

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We conducted this review to evaluate the effectiveness of interventions on weight related outcomes (BMI z-score, BMI percentile and body fat percentage) and lifestyle outcomes (physical and sedentary activities, and dietary behaviour) among overweight or obese schoolchildren.

Our narrative synthesis found studies that incorporated behavioural lifestyle interventions reported positive effects on weight related outcomes. Previous reviews and meta-analyses reported interventions that incorporate lifestyle modifications including dietary restriction, physical activities (exercise) alone or in combination leads to larger effects on BMI, BMI z-scores and body composition, as well as reduced unhealthy dietary intake when compared to controls [ 9 , 32 , 33 ]. Moreover, a previous systematic review found addition of pharmacological intervention to behavioural lifestyle intervention led to only small effects on BMI and BMI z-score. [ 33 ]. Hence, this emphasised that behavioural lifestyle modification is utmost important in the management of obesity in children.

Studies that integrated behavioural skills into the lifestyle modifications intervention showed positive effects on the reductions of BMI z-scores, BMI percentile, waist circumference and body fat, as well as improved physical, sedentary and dietary behaviours. The parents of children in the trials were taught coping and problem-solving skills, which could have facilitated the weight reduction, hence, improved outcomes. A previous case control study that examined family functioning, expressed emotion and coping skills found mothers’ negative expressed emotion and coping skills were related to the child being overweight [ 34 ]. Hence, such behavioural skills should be incorporated as strategies in the management of obesity in children.

In this review, all studies that engaged family members in their intervention showed positive effects on weight related outcomes. Such findings are consistent with previous reviews which reported family based interventions with parental involvement led to reductions in BMI, BMI z-scores and body composition [ 32 , 35 ]. The engagement of parents in these trials facilitated their children in choosing healthier behaviour in addition to acting as role models for their children.

In most studies with positive effects, the delivery of the intervention involved interdisciplinary approaches involving various healthcare practitioners including dietitians, psychologists and physical or sports therapists. Moreover, in some of these studies, intervention sessions were conducted in groups. A previous systematic review on childhood obesity showed that behavioural lifestyle interventions delivered by trained specialised interventionists were effective for obesity [ 36 ]. Continuous external support from other people, or professionals may be important in achieving and maintaining goals.

Our review found that the studies were set in various settings, including in the community, school, home and the hospital. All community-based interventions reported positive effects on the primary outcomes. Our findings are consistent with previous systematic reviews which reported positive outcomes from combined lifestyle interventions (diet and physical activity) delivered in the community [ 36 ]. It was anticipated that community-based interventions would be more cost-effective compared to clinic or hospital settings. An economic evaluation on 10 RCTs reported lifestyle interventions are potentially cost-effective for obese children between 10 and 11 years of age. Its impact on health benefits and cost-savings however, would only be evident in their 6 th or 7 th decade of life [ 37 ].

The outcome measured in majority of the studies varied. Various reference datasets for weight related outcomes were used, which led to different definitions of obesity in children. The BMI z-score was often used as an outcome measure in children, however, its role in childhood obesity has been challenged. In children aged less than 9 years, BMI z-score is a weak to moderate predictor of total fat mass and body fat percentage [ 38 ]. In addition, it is also a weak predictor of total body fat changes over time with poor specificity [ 39 , 40 ]. Hence, in clinical practice, changes in body composition among obese children should not solely be monitored using BMI z-score.

Our meta-analyses showed the effects of interventions on BMI z-score, waist circumference and body fat measurements were inconclusive for the management of childhood obesity. We are not able to make comparison with a previous review [ 9 ] as they pooled standard BMI data rather than BMI z-score, waist circumference or body fat. Further their review also included adolescents. The inconclusive findings from our meta-analyses could be due to differences in intervention strategies.

Our review provides insight into the impact of lifestyle interventions combined with behavioural strategies in reducing the weight related outcomes among overweight and obese schoolchildren. The involvement of family members in the treatment of overweight and obesity could not be overemphasised. The intervention one chooses would depend on the resources in the school and the community. Using dedicated personnel to deliver the intervention was effective, but the cost and human resources demand would be high. In addition, strategies attempting to reduce unhealthy behaviours such as reducing sedentary behaviours and adopting healthy dietary intake seem to be more effective. Parents could be trained and empowered to promote the lifestyle changes required for the management of obesity in children [ 41 ].

This review included both randomized and non-randomized controlled trials to provide more comprehensive views of various interventions aimed to reduce weight related outcomes. We also evaluated the effects of intervention on waist circumference and body fat percentage not just on BMI measures as these parameters are commonly monitored in clinical practice. Several limitations need to be mentioned in this review. Even though we have employed an extensive search strategy, we limited the publications to English language only, due to limited resources. Hence, the effectiveness of the interventions could be overrepresented. Our review only included RCTs and quasi-experimental studies, and not cohort studies. The latter study design would provide a better reflection of clinical practice. Our search strategy was specific for diet, nutrition and physical activity interventions. Hence, publications that used term such as weight management were not captured. Most studies included in this review had high or unclear risk of bias with regards to the allocation concealment and blinding of the assessors. Therefore, the findings reported should be interpreted with caution. Most studies also had high or unclear risk of bias for blinding of participants and personnel. However, these were unavoidable in view of the nature of the intervention. In addition, unpublished studies were not identified, thus, publication bias is possible. The funnel plot showed presence of possible publication bias which could be attributed to studies with small sample size and possibly with negative results were not published. Cost-effectiveness of interventions were not included in this review, which is an important aspect to consider when choosing an intervention. Hence, it should be considered in future reviews.

Our meta-analyses showed that current interventions for the management of obesity among schoolchildren on weight related outcomes were inconclusive. However, based on the narrative synthesis, the role for behavioural lifestyle interventions with interdisciplinary team approaches and family involvement is crucial to curb obesity among schoolchildren. But more robust studies are needed to determine its effectiveness.

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Elsevier

Journal of Pediatric Nursing

Articles systematic review of childhood obesity prevention.

This systematic review identified the current state of the evidence related to the prevention of obesity in young children. The results indicate five areas of emphasis in the literature: prevalence of the problem; prevention as the best option; preschool population as the target; crucial parental involvement; and numerous guidelines. Because the gap between clear articulation of the problem as well as population and the best strategies to impact the prevention of the problem is evident, health care practitioners must be involved in well-constructed implementation and evaluation studies that build on the limited base of current evidence.

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