Long-Term Dietary and Physical Activity Interventions in the School Setting and Their Effects on BMI in Children Aged 6–12 Years: Meta-Analysis of Randomized Controlled Clinical Trials

Preventive actions and potential obesity interventions for children are mainly researched throughout the school period, either as part of the school curricula or after regular school hours, via interventions mostly lasting less than 12 months. We aimed to perform a meta-analysis on randomized controlled clinical trials to evaluate the evidence of the efficacy of long-term school-based interventions in the management of childhood obesity in terms of BMI from a dietary and physical activity-based approach. Eleven randomized controlled clinical trials were examined using the random effects model, and the results showed that there were no significant effects associated with physical activity + nutrition intervention in school children aged 6–12 years, with a pooled standardized mean difference (SMD) (95% CI) of −0.00 (−0.05, 0.04). No effects were observed after subgroup analysis based on the intervention length. The findings from our study indicate that long-term school-based interventions on physical activity and dietary habits received by children aged 6–12 years seem to have no effect on BMI. However, the promotion of such interventions should not be discouraged, as they promote additional positive health outcomes for other domains of children’s health.