<![CDATA[The decline in physical activity among urban adolescents has become a significant public health concern due to its association with increased risks of obesity, metabolic disorders, cardiovascular diseases, and poor mental health. This study aimed to evaluate the effectiveness of social media-based health promotion interventions in increasing physical activity among urban adolescents and to identify factors contributing to intervention success. A quasi-experimental study with a non-equivalent control group design and pre-test and post-test measurements was conducted among 80 adolescents aged 15–18 years. The intervention was delivered over 4–8 weeks through social media platforms using educational content, physical activity demonstration videos, weekly challenges, self-monitoring activities, and peer interactions based on Social Cognitive Theory and the Theory of Planned Behaviour. The intervention group showed a significant increase in physical activity of +655 MET-minutes/week (p<0.001), while the control group showed no significant change. Multiple regression analysis (R²=0.58) revealed that social media intervention (β=0.62), participant engagement (β=0.41), and frequency of social media access (β=0.28) significantly predicted increased physical activity. Activities promoted included brisk walking, light jogging, cycling, aerobic exercise, bodyweight training, dancing, and recreational sports, supporting integration into school- and community-based health promotion programs. Overall, social media-based interventions effectively increased physical activity among urban adolescents regardless of gender or nutritional status. Structured and interactive digital content enhanced self-efficacy, motivation, and sustainable behavioural change beyond passive information exposure.]]>
