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School-Based Physical Activity Gains in Adolescents Fade After Six Months
A systematic review and meta-analysis of 90 randomised controlled trials found that school-based physical activity interventions produced a modest but statistically significant short-term increase in adolescent activity levels (SMD = 0.41, 95% CI = 0.23–0.59), but these gains did not persist beyond six months of follow-up. The positive short-term signal is encouraging, yet the absence of durable effects underscores a fundamental challenge in translating school-based programmes into lasting behavioural change.
What Was Studied
The review examined whether structured physical activity interventions delivered within school settings can meaningfully improve activity levels, fitness, sedentary behaviour, and body mass index (BMI) among adolescents aged 10–19 years. The question carries public health urgency given that physical inactivity in this age group is a recognised driver of rising obesity, noncommunicable disease burden, and deteriorating mental health outcomes globally.
How It Was Studied
This was a systematic review and meta-analysis conducted in accordance with PRISMA guidelines, drawing on searches across five major databases — Scopus, Embase, CINAHL, PubMed, and Cochrane — covering publications from 2000 onward. Eligible studies were randomised controlled trials involving adolescents aged 10–19 years in school-based settings, compared against control conditions receiving no structured intervention. Across the 90 qualifying studies, approximately 17,000 adolescents were included in the pooled analyses. Intervention types spanned multicomponent programmes, dedicated activity lessons, educational awareness sessions, and organised after-school activities. Risk of bias was assessed using the Cochrane ROB 2 tool, and evidence quality was graded using the GRADE framework.
What Was Observed
- Modest short-term benefit on physical activity: Over the 0–6 month window, school-based interventions produced a small-to-moderate increase in physical activity levels compared with controls — roughly equivalent to a standardised mean difference of 0.41 (95% CI = 0.23–0.59). This is a statistically significant and directionally consistent result, though classified as low-certainty evidence, meaning the true effect could be meaningfully smaller.
- No sustained long-term effects: When follow-up extended beyond six months, pooled analyses revealed no significant continuation of the activity gains. Effects on overall physical activity, sedentary behaviour, and BMI were all non-significant at longer time horizons, suggesting that the behaviour change achieved during programme delivery was not maintained once structured support was removed.
- Broad range of intervention formats with high variability: The included trials tested diverse programme designs across varied school environments and cultural contexts, contributing to substantial heterogeneity in the pooled estimates. This variability limits the precision of any single summary estimate and makes it difficult to identify which specific programme elements drive benefit.
Why This Matters
Schools represent one of the most scalable and equitable platforms for reaching adolescents, making this evidence base strategically important for public health planning. The finding that short-term gains exist but erode quickly shifts the research and policy question from whether school-based interventions work to how they can be designed for durability. The authors suggest that sustaining change may require coordinated, system-level strategies that extend beyond the school gates to involve families and communities rather than relying on time-limited, school-only programmes.
How to Read This Result
Given the medium overall quality signal, the low-to-moderate GRADE certainty ratings, and the high heterogeneity across included studies, the short-term positive effect (SMD = 0.41) should be interpreted as a directionally reliable but imprecise estimate — one that warrants cautious optimism rather than confident prescription of any specific programme model.
Limitations
High heterogeneity across the 90 included studies complicates interpretation of the pooled estimates and may reflect differences in programme intensity, cultural context, measurement tools, and population characteristics. The overall certainty of evidence ranged from low to moderate under GRADE criteria, meaning future research could plausibly alter the conclusions. Critically, the absence of significant effects beyond six months was a consistent pattern, highlighting the limitation of short intervention windows and the difficulty of detecting sustained behavioural change in this age group.