Association Between Exercise Behavior Stages and Obesity Transition in Children and Adolescents: A Nationwide Follow-Up Study

<b>Backgrounds:</b> To examine the association between stages of exercise behavior change, as defined by the transtheoretical model (TTM), and obesity progression among Chinese children and adolescents, with attention to gender and urban-rural differences. <b>Methods:</b> A total of 5006 Chinese children and adolescents aged 9-18 years were assessed in 2019 and followed up in 2020. Participants were categorized into five TTM stages: precontemplation, contemplation, preparation, action, and maintenance. Logistic regression models evaluated the associations between the TTM stages and obesity outcomes, including incident obesity and transitions from normal or overweight to obesity. Analyses were stratified by gender and urban-rural residence, and interaction effects were tested. <b>Results:</b> Compared to the maintenance stage, precontemplation (OR = 2.08, 95% CI: 1.45-2.99) and contemplation (OR = 1.48, 95% CI: 1.05-2.08) stages had higher obesity risk, with similar trends in follow-up incident obesity (precontemplation: OR = 1.63, 95% CI: 1.17-2.28; contemplation: OR = 1.47, 95% CI: 1.10-1.98). These associations were more pronounced among boys and rural residents. Significant interactions were observed between TTM stages, sex (<i>p</i> = 0.029), and residence (<i>p</i> = 0.005) in obesity transition. <b>Conclusions:</b> Exercise behavior stages are associated with obesity progression, particularly among boys and rural children. These findings underscore the importance of stage-specific interventions tailored to individual readiness for behavior change and contextual factors.