The present study examined reports of changing eating to manage weight/shape over one year among adolescents. It also tested how changing eating for weight/shape was associated with physical activity (resistance training, moderate-to-vigorous physical activity; MVPA) and mental health (depressive symptoms, flourishing), and whether weight perceptions moderated these associations.

Participants were Canadian adolescents (N = 20,614, Mage ± SD = 14.4 ± 1.3, 52.9% girls) who completed self-report surveys in the 2020–2021 and 2021–2022 waves of the COMPASS study. Separate multilevel models were tested for each outcome.

Approximately 30% of adolescents reported changing their eating to manage weight/shape at least once a week. More days of changing eating were associated with significantly higher depressive symptoms and lower flourishing cross-sectionally (b = 0.51, b = −0.27) and over time (b = 0.35, −0.20); the flourishing association over time was weaker for adolescents who perceived themselves as overweight relative to about right. More days of changing eating were also associated with more MVPA and resistance training cross-sectionally (b = 2.81, b = 0.19) and over time (b = 1.28, b = 10). The relationship between changing eating and MVPA over time was stronger for adolescents who perceived themselves as overweight relative to about right; whereas the cross-sectional relationship between changing eating and resistance training was weaker.

Reports of changing eating to manage weight/shape were associated with divergent health outcomes; research into how and to what extreme adolescents are changing eating to manage weight/shape, and identity factors that may contribute to these differences, is warranted.