School-based physical activity interventions increase adolescent activity short-term but not long-term

BACKGROUND: Physical inactivity among adolescents is a significant challenge contributing to rising cases of obesity, noncommunicable diseases (NCD), and mental health challenges. A viable strategy is the promotion of physical activity (PA) in the school setting. We conducted a systematic review and meta-analysis to assess the efficacy of school-based physical activity interventions, compared to control conditions, in improving activity outcomes in adolescents. METHODS: We followed PRISMA guidelines and searched Scopus, Embase, CINAHL, PubMed, and Cochrane from 2000 onwards for relevant studies in English. We included randomised controlled trials (RCTs) involving adolescents aged 10-19 years with interventions in school-based settings and outcomes including activity, fitness, sedentary behaviours, and body mass index (BMI). We conducted a meta-analysis of included studies, assessed them using the Risk of Bias (ROB) 2 tool from the Cochrane handbook, and evaluated evidence quality through the GRADE framework. RESULTS: The search yielded 30 629 records, of which 90 studies including approximately 17 000 adolescents met the inclusion criteria. Interventions included multicomponent programmes, activity lessons, educational awareness sessions, and after-school activities. In the short term (0-6 months), school-based interventions significantly increased physical activity levels (standardised mean difference (SMD) = 0.41, 95% confidence interval (CI) = 0.23-0.59; low-certainty evidence). However, these improvements were not sustained beyond six months of follow-up, with pooled analyses showing no significant long-term effects on overall activity, sedentary behaviour, or BMI. CONCLUSIONS: School-based interventions can modestly increase adolescents' physical activity in the short term, but their effects diminish over time. Sustaining behavioural change may require long-term, system-level strategies that involve schools, families, and communities. Overall, the certainty of evidence was low to moderate, and findings should be interpreted with caution due to high heterogeneity across studies.