Perceived social support may mediate adiposity outcomes after nutrition and exercise intervention in adolescents with overweight

This study evaluated whether an 8-week nutrition and exercise intervention improved adiposity and estimated basal metabolic rate outcomes in adolescents with overweight and explored perceived social support and exercise self-efficacy as psychosocial mediators of outcomes at three-month follow-up. Ninety-four adolescents aged 10–14 years from Guangzhou, China, were randomized 1:1 to the intervention or usual-care control group; 78 participants (39 per group) provided complete data for the analyses reported here. The intervention included supervised aerobic or resistance exercise three times weekly for 30 min per session and a 15-min group nutrition education class once weekly for 8 weeks. Controls received usual-care health advice without scheduled exercise or nutrition sessions. BMI, fat mass, and estimated basal metabolic rate (BMR) were measured by bioelectrical impedance at baseline, 8 weeks, and three-month follow-up. Perceived social support and exercise self-efficacy were evaluated as candidate mediators. ANCOVA-framework linear models and exploratory parallel mediation analyses with 5,000 bootstrap resamples were used. At 8 weeks, the intervention group had lower BMI and fat mass and higher estimated BMR than the control group after adjustment for baseline values and covariates; the reported 95% confidence intervals excluded zero. In the three-month mediation models, perceived social support showed significant specific indirect effects for BMI, fat mass, and estimated BMR. In contrast, no specific indirect effect through exercise self-efficacy was detected because its 95% confidence interval included zero for each outcome. The intervention was associated with favorable adiposity and estimated BMR outcomes, and exploratory mediation analyses identified perceived social support as a potential pathway for maintained outcome differences at three months. Because physical activity and dietary behavior were not measured during follow-up, these findings should not be interpreted as evidence that adolescents sustained physical activity or dietary behavior after the program. Clinical Trial Registry: ChiCTR2500110816.