Efficacy of a Digital Peer Support Program on Weight Management and Mental Health in University Students With Preobesity: Randomized Controlled Trial

Background: Approximately one-third of university students are overweight or obese, and a similar proportion experience anxiety or depression. Despite the interrelated nature of weight and mental health, interventions rarely address these issues simultaneously in young adults. Digital peer support interventions have the potential to promote healthy lifestyle and mental well-being. However, evidence is limited on whether a digital peer-driven approach can concurrently improve weight management and mental health in university populations with preobesity. Objective: This randomized controlled trial (RCT) evaluated the efficacy of a digital peer support program in concurrently improving weight management and mental health outcomes among university students with preobesity. Methods: In a single-blind parallel group RCT, 216 students with preobesity were allocated equally among three 6-month arms, which were a peer support intervention, an active wellness control, and a waitlist control. The peer support arm began with an interactive online workshop followed by moderated WeChat (Tencent) group discussions, daily micro tasks, biweekly group challenges, and digital badges to reinforce engagement. The active control group received the same schedule and formats but focused on general wellness topics. The waitlist group completed the same assessments without any intervention during the study period. The primary outcome measured the change in BMI from baseline to 6 months. Secondary outcomes included weekly physical activity measured in metabolic equivalent of task minutes, self-esteem, loneliness, anxiety, and depression assessed at 0, 2, 4, and 6 months. Analyses used linear mixed effects models. Results: Retention exceeded 90%. At 6 months, the peer-support group achieved a greater BMI reduction than the active control by 0.47 (95% CI -0.89 to -0.04) kg/m² and waitlist by 0.54 (95% CI -0.85 to -0.01) kg/m². Weekly metabolic equivalent of task-minutes was 129.5 higher than active control (95% CI 53.3-205.6) and 152.9 higher than waitlist (95% CI 68.4-237.4). Self-esteem increased by 1.81 points versus active control (95% CI 0.22-3.39) and 1.99 points versus waitlist (95% CI 0.21-3.76). Loneliness scores fell by 3.79 points relative to active control (95% CI -7.03 to -0.56) and by 5.02 points relative to waitlist (95% CI -8.38 to -1.66). No significant differences emerged for anxiety or depression. Conclusions: A comprehensive digital peer-support program delivered via WeChat produced modest but clinically meaningful improvements in weight management, physical activity, self-esteem, and social connectedness among undergraduates with preobesity compared with wellness control and no intervention. These findings suggest that integrating peer support into scalable digital platforms can simultaneously address physical and psychosocial health in at-risk university populations.