Social connections with family and friends in adolescence: Shaping body mass index trajectories into adulthood

Objectives: To investigate whether adolescent social connections influence body mass index (BMI) trajectories into adulthood and explore whether associations are moderated by gender, ethnicity or age. Methods: Data came from 17,719 American adolescents in grades 7-12 at baseline (1994-95) from the National Longitudinal Study of Adolescent to Adult Health. Growth curve models tested associations between baseline social connections and BMI trajectories from waves II-V including interactions for gender, ethnicity and age. Results: Stronger peer connections were associated with flatter BMI trajectories. For example, BMI for those with high peer contact was 0.79 kg/m2 lower [95% CI-1.20,-0.38] 22 years after baseline, compared to those with low contact. Stronger family connections were associated with steeper trajectories. For example, BMI for those with high family contact was 0.52 kg/m2 higher [95% CI 0.01, 1.02] 22 years after baseline, compared to those with low contact. Discussion: Among adolescents, stronger peer connections were associated with flatter BMI trajectories and stronger family connections with steeper trajectories. Promotion of peer-based interventions could be explored as a strategy to promote healthy weight trajectories.