The prospective associations between internalized weight bias and physical activity among adolescents.

This study examined the associations between internalized weight bias and physical activity (resistance training, moderate-to-vigorous physical activity; MVPA) across weight perceptions over one year among Canadian adolescents. Participants in Years 10 (T1; 2021-2022) and 11 (T2; 2022-2023) of the COMPASS study completed a cross-sectional self-report survey each year (N = 23,574, Mage = 14.3 (SD = 1.2), 51.5 % cisgender girls). Linear mixed effects multilevel models stratified by weight perception (underweight, about the right weight, overweight) tested the association between T1 internalized weight bias and T2 physical activity after controlling for province, gender, ethnicity, perceived affluence, age, and T1 physical activity. Adolescents with overweight perceptions reported higher internalized weight bias (ηp2 = .05) and lower MVPA (ηp2 = .004) and resistance training (ηp2 = .01) than adolescents with lower-weight perceptions. For adolescents with underweight and about the right weight perceptions, internalized weight bias was associated with more MVPA [b(SE) = 6.8(3.0); 3.7(1.4)] and resistance training [b(SE) = .33 (.12); .11(.06)] one year later compared to adolescents reporting no internalized weight bias. Physical activity levels were not different across levels of internalized weight bias among adolescents with overweight perceptions. The differing associations between internalized weight bias and physical activity across weight perceptions may relate to broader anti-fat attitudes and experiences of stigma that uniquely impact adolescents with overweight perceptions. Future research should consider the physical activity motivations associated with internalized weight bias.