Adolescent weight control behaviours and adult depressive symptom and body mass index trajectories

Importance: In adolescence, attempts to lose weight are common, but their long-term impacts on mental and physical health are not known. Objective: To investigate the association between adolescent dieting and exercising to lose weight and adult trajectories of depressive symptoms and body mass index (BMI). Design: A longitudinal cohort study of children born between April 5 and 11, 1970, and followed up to age 51 years. Setting: Adolescents in the 1970 British Cohort Study in England, Wales and Scotland. Participants: A total of 4,650 adolescents with available exposure data. Exposures: Self-reported lifetime dieting or exercising for weight loss measured at age 16 years. Main Outcomes and Measures: Depressive symptoms measured with the nine-item Malaise Inventory, and BMI derived from self-reported height and weight, at ages 26, 30, 34, 42, 46, and 51 years. Results: Among 4,650 adolescents (56.7% girls, 97.7% White), 1,938 (41.7%) had dieted and 343 (7.4%) had exercised for weight loss by age 16 years. In fully adjusted analyses controlling for a wide range of child- and family-based confounders including prior BMI and emotional difficulties, there was evidence that adolescents who had dieted had higher adult depressive symptom trajectories (adjusted mean difference [aMD] 0.13, 95% CI 0.03-0.24, p=0.015) and higher and increasing adult BMI trajectories than those who had not dieted. There was also evidence that adolescents who exercised for weight loss had higher adult depressive symptom (aMD 0.18, 95% CI 0.02-0.34, p=0.031), and BMI trajectories (aMD 0.37, 95% CI -0.03, 0.78, p=0.071), though evidence of the latter was weak. Conclusions and Relevance: Behaviours aimed at weight loss occurring in adolescence might be a shared risk factor for depressive symptoms and high BMI in adulthood. If causal, these findings could suggest that reducing pressures to lose weight in adolescence may help prevent poor mental and physical health across the lifecourse.