Adolescents bullying and young adults body mass index and obesity: a longitudinal study

Objective: To examine whether adolescent males and females who were victims of bullying were at greater risk of a higher body mass index (BMI) and obesity by young adulthood. Design: Secondary analysis of data from a community-based cohort study. Subjects: A sub-sample of 1694 offspring (50% males) who were participants in the Mater-University of Queensland Study of Pregnancy (MUSP), Brisbane, and who provided bullying information at 14 years and physical assessment at 21 years. Main Outcome Measures: BMI and its categories as normal, overweight or obese at 21 years. Results: One in two adolescent males and one in three adolescent females reported that they had been bullied at school by others. We found that adolescent males and females who were bullied were at a significantly greater risk of a higher BMI and obesity by young adulthood. Fourteen-year-old males who were occasionally/often bullied at school had 0.64 (95% confidence interval (CI): 0.02, 1.27) kg m 2 greater mean BMI by 21 years compared with males who were never bullied by 14 years. This mean difference in BMI was 1.52, (95% CI: 0.75, 2.29) kg m 2 for females. Similarly, the odds of being obese were 2.54 (95% CI: 1.58, 4.09) times at 21 years for those males who were bullied occasionally/often compared with adolescent males who were never bullied. For females, this was 2.18 (95% CI: 1.40, 3.39). Overweight adolescents who experienced bullying had the greatest increase in BMI by young adulthood. Adjusting for potential confounding or mediating factors, the associations remain strong for males but are attenuated for females. Conclusions: The findings of this study suggest that both male and female adolescents who were bullied often/sometimes by their peer group at 14 years were at greater risk of higher BMI and obesity by young adulthood.