School-based physical activity and nutritional education interventions on body mass index: a meta-analysis of...

To evaluate the effect of school-based physical activity (PA) and nutritional education (NE) interventions on children's and adolescents' body mass index.

We conducted a systematic search in fourteen databases until September 2012 for randomised controlled trials on PA and NE, conducted in the school setting, and delivered to children and adolescents. Additionally, we performed a cross-reference check in related papers. The title and abstract review and the quality assessment were performed by two independent researchers. The software EPPI-Reviewer3 was used to store, manage and analyse all data. The meta-analysis was conducted using the random-effects model, and the outcomes were reported as standardised mean difference (SMD). As a secondary analysis, we pooled together the interventions that considered PA or NE alone.

Thirty-eight studies met the eligibility criteria. The main analysis showed a SMD between intervention and control groups of -0.03 (95% CI: -0.09, 0.04; n=28,870; I(2)=83%). When we considered all 57 trials, there was no difference between the results of the primary analysis.

The synthesis of school-based PA and NE interventions showed no statistically significant mean reduction on children's and adolescents' body mass index. The high heterogeneity among studies requires caution in the generalisation of the results.