BACKGROUND: This meta-analysis study aims to assess the efficacy of school-based and after-school intervention programs on the BMIs of child and adolescents, addressing the correlation between some moderating variables.
METHODS: We analyzed 52 studies (N = 28,236) published between 2000-2011.
RESULTS: The overall effect size was 0.068 (P < .001), school (r = .069) and after-school intervention (r = .065). Programs conducted with children aged between 15-19 years were the most effective (r = .133). Interventions programs with boys and girls show better effect sizes (r = .110) than programs that included just girls (r = .073). There were no significant differences between the programs implemented in school and after-school (P = .770). The effect size was higher in interventions lasting 1 year (r = .095), with physical activity and nutritional education (r = .148), and that included 3-5 sessions of physical activity per week (r = .080). The effect size also increased as the level of parental involvement increased.
CONCLUSIONS: Although of low magnitude (r = .068), the intervention programs had a positive effect in prevention and decreasing obesity in children. This effect seems to be higher in older children's, involving interventions with physical activity and nutritional education combined, with parent's participation and with 1-year duration. School or after-school interventions had a similar effect.