Nudge-Based Exercise Intervention for Adolescents With Obesity

This study will evaluate whether a nudge-based exercise program can improve body mass index (BMI) and physical activity in adolescents with obesity. About 140 adolescents aged 10-19 years will participate. Participants will be placed into one of two groups according to the order in which they are admitted to the hospital. One group will receive a standard exercise intervention, while the other group will receive an 8-week nudge-based exercise program designed to make regular physical activity easier to start and maintain. The nudge-based program uses simple behavioral strategies to make exercise easier to start and maintain, including framed and visual information, default exercise options, reminders, peer comparison and support, goal commitment, progress feedback, and small incentives. The program combines face-to-face sessions during hospitalization with home-based support, exercise tools, activity recording, and online follow-up. The main outcomes are changes in BMI and physical activity. Other outcomes include body composition, blood metabolic markers, health-related quality of life, and exercise self-efficacy. Assessments will be conducted before and after the intervention, with follow-up assessments used to examine whether the effects are maintained over time.

Inclusion Criteria: * Aged 10-19 years. * Body mass index (BMI) at or above the 95th percentile for age and sex according to the Chinese BMI screening criteria for overweight and obesity in children and adolescents. * Able to communicate and understand study instructions. * Willing to participate in the study and provide written informed consent, with informed consent from a parent or legal guardian as required. Exclusion Criteria: * Known secondary causes of obesity, including hypothalamic, endocrine, genetic, or syndromic obesity. * Use of anti-obesity medications, including injectable glucagon-like peptide-1 (GLP-1) receptor agonists, within 3 months before enrollment. * Severe cardiovascular or cerebrovascular disease, severe hepatic or renal dysfunction, or other serious organic diseases that may affect participation or study outcomes. * Psychiatric disorders or cognitive impairment that may interfere with participation or completion of study assessments. * Current participation in another weight-loss, structured exercise, or other intervention program that may affect body weight or physical activity. * Any contraindication to exercise or medical or physical condition that substantially limits participation in the prescribed exercise program.