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Meta-Analysis
. 2009 Mar 31;180(7):719-26.
doi: 10.1503/cmaj.080966.

Effect of school-based physical activity interventions on body mass index in children: a meta-analysis

Kevin C Harris  1 , Lisa K Kuramoto, Michael Schulzer, Jennifer E Retallack
Affiliations
Meta-Analysis

Effect of school-based physical activity interventions on body mass index in children: a meta-analysis

Kevin C Harris et al. CMAJ. .

Abstract

Background: The prevalence of childhood obesity is increasing at an alarming rate. Many local governments have enacted policies to increase physical activity in schools as a way to combat childhood obesity. We conducted a systematic review and meta-analysis to determine the effect of school-based physical activity interventions on body mass index (BMI) in children.

Methods: We searched MEDLINE, EMBASE, CINAHL and the Cochrane Central Register of Controlled Trials up to September 2008. We also hand-searched relevant journals and article reference lists. We included randomized controlled trials and controlled clinical trials that had objective data for BMI from before and after the intervention, that involved school-based physical activity interventions and that lasted for a minimum of 6 months.

Results: Of 398 potentially relevant articles that we identified, 18 studies involving 18 141 children met the inclusion criteria. The participants were primarily elementary school children. The study duration ranged from 6 months to 3 years. In 15 of these 18 studies, there was some type of co-intervention. Meta-analysis showed that BMI did not improve with physical activity interventions (weighted mean difference -0.05 kg/m(2), 95% confidence interval -0.19 to 0.10). We found no consistent changes in other measures of body composition.

Interpretation: School-based physical activity interventions did not improve BMI, although they had other beneficial health effects. Current population-based policies that mandate increased physical activity in schools are unlikely to have a significant effect on the increasing prevalence of childhood obesity.

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Figures

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Figure 1: Weighted mean difference in change in body mass index (BMI) between the intervention group (school-based physical activity) and the control group. The size of each data marker indicates the weight assigned to the individual study. These weights are proportional to the inverse of the variance for each study. Larger studies tend to have less variance (because of sample size) and therefore receive more weight. Note: CI = confidence interval.
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Figure 2: Sensitivity analysis for weighted mean difference in change in body mass index (BMI) between the intervention group (school-based physical activity) and the control group. Note: CI = confidence interval.
See this image and copyright information in PMC

Comment in

  • Tackling the epidemic of childhood obesity.
    Baur LA. Baur LA. CMAJ. 2009 Mar 31;180(7):701-2. doi: 10.1503/cmaj.090196. CMAJ. 2009. PMID: 19332745 Free PMC article. No abstract available.
  • Interpret results with caution.
    Lyn R, McCarty F. Lyn R, et al. CMAJ. 2009 Jun 23;180(13):1330; author reply 1330. doi: 10.1503/cmaj.1090031. CMAJ. 2009. PMID: 19546463 Free PMC article. No abstract available.

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