Impact of School-Based Physical Activity Intervention on Obesity and Physical Parameters in Children: A Systematic Review

<b>Background:</b> Childhood obesity continues to pose a major global health challenge, and schools offer a structured and scalable setting for implementing physical activity programs. However, the effectiveness of these interventions remains inconsistent. This systematic review synthesizes evidence from school-based physical activity interventions and evaluates their impact on obesity-related parameters, physical activity levels, physical fitness, and cardiorespiratory fitness among children. <b>Methods:</b> A comprehensive search of PubMed, Scopus, and the Cochrane Library identified randomized controlled trials published between January 2015 and March 2025. Eligible studies included children aged 5-18 years and assessed school-based physical activity interventions. Outcomes included BMI, body fat percentage, physical activity levels (including MVPA), physical fitness, and cardiorespiratory fitness. Due to methodological heterogeneity, a narrative synthesis was conducted. <b>Results:</b> A total of 28 studies met inclusion criteria. Among the 16 studies reporting obesity-related outcomes, 7 demonstrated statistically significant improvements in BMI or BMI z-scores, while 6 of 16 (37.5%) showed no measurable effect. Reductions in body fat percentage were more consistently observed (5 of 6 studies). Both short-term (<6 months) and long-term (>12 months) interventions showed comparable proportions of studies with statistically significant BMI improvements (~50%). For physical activity outcomes, 5 of 11 studies reported increased MVPA, whereas others showed no significant change. Sedentary behavior outcomes were mixed, with only 2 of 6 studies demonstrating significant reductions. Improvements in physical fitness were reported in two-thirds of studies, while cardiorespiratory fitness improvements were inconsistent, with significant gains observed primarily in higher-intensity or well-structured programs. Across outcomes, several findings were statistically significant but modest in clinical magnitude. <b>Conclusions:</b> School-based physical activity interventions have the potential to improve select obesity-related parameters, particularly body fat percentage and BMI in a subset of studies. However, effects on MVPA, sedentary time, overall activity levels, and cardiorespiratory fitness remain variable. The effectiveness of these programs appears influenced by intervention structure, intensity, and adherence rather than duration alone. Future interventions should incorporate tailored, multi-component approaches to enhance both clinical relevance and long-term sustainability. While several effects were statistically significant, most were modest in magnitude. However, even modest improvements in BMI z-score, body fat percentage, and fitness can be meaningful at a population level, particularly when delivered through universal, scalable school platforms that reach large numbers of children.