Longitudinal Associations between Weight Self-Stigma, Physical Exercise, and Social Anxiety among Adolescents: Between-and Within-Person Effects.

Adolescent mental health, particularly the complex relationship between weight self-stigma and social anxiety, has received limited research attention. Previous studies have often overlooked the need for longitudinal investigations to understand how these factors influence each other over time, as well as the potential mediating role of physical exercise, particularly regarding gender differences.This study employed a three-wave longitudinal design 93-month intervals) with 637 Chinese adolescents (aged 12-18, M = 15.29 years; 283 Males, 354 females). Using the Random Intercept Cross-Lagged Panel Model (RI-CLPM), we examined associations among weight self-stigma, physical exercise, and social anxiety, controlling for age and self-weight perception. Measures included the Weight Self-Stigma Scale, Adolescent Social Anxiety Scale, and Physical Activity Rating Scale.At the between-person level, weight self-stigma positively correlated with social anxiety (β = 0.59, p < .001), while physical exercise negatively correlated with weight self-stigma (β=-0.53, p < .001) and social anxiety (β= -0.68, p < .001). Within-person analyses revealed bidirectional predictions: weight self-stigma predicted subsequent social anxiety (T1-T2:β = 0.24,p < .001,T2-T3:β = 0.17,p < .01), and social anxiety predicted weight self-stigma (T2-T3:β = 0.29, p < .001). Physical exercise mediated both pathways with small but significant effects (β = 0.08, 95%CI[0.02,0.14], β = 0.06 ,95%CI[0.03,0.12]), with no gender differences(p = .11 > .05).Physical exercise disrupts the reciprocal reinforcement between weight self-stigma and social anxiety in Chinese adolescents, highlighting its potential as a gender-inclusive intervention target. Findings emphasize the need to integrate physical activity into mental health strategies to address body image-related distress.