Kevin C Harris, Lisa K Kuramoto, Michael Schulzer, Jennifer E Retallack
Journal: CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne 2009;180(7):719-26
PMID: 19332753
This is an overview of the evidence for the effect of school-based physical activity on body mass index in children. This meta-analysis included 18 primary studies published to 2008. It involved 18 141 children of school age (5-18years). Studies were selected if children in the intervention group received a school-based physical-activity programme during school time for 6 months or more. The control group did not received the intervention and continued with their existing physical education curriculum. This meta-analysis found that the change in BMI was not significantly different between children who received the physical activity intervention and those in the control group. The school-based physical activity interventions did not improve BMI. However, important weaknesses were observed in the studies included in the meta-analysis. There was a lack of assessment of adherence to study protocols. There was also a lack of objective assessment of the ‘dose’ (type, duration, frequency) of physical activity in these studies. The authors conclude that physical activity should be included and promoted within schools, as an important component of a healthy lifestyle, but that further studies that address methodological weaknesses are needed. School-based physical activity can be widely promoted as a solution for childhood obesity.
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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