The Impact of Adolescent Body Weight Misclassification on Dieting Behaviour From Adolescence to Adulthood: A Longitudinal Study

INTRODUCTION: Weight misclassifications and consequent uptake of weight loss activities may influence future eating habits and weight trajectories. This study examines the longitudinal association between body weight misclassifications in adolescence and its impact on dieting patterns from adolescence to adulthood. METHODS: Data were retrieved from an Australian longitudinal birth-cohort study. The analytical sample (n = 1132) comprises participants whose measured and perceived body weight at 14 years of age were recorded and prospectively provided dieting information at 14, 21 and 30 years of age. Weight misclassification was determined by comparing measured body mass index with perceived body weight. RESULTS: The proportion of participants who reported dieting increased from 19% at 14-year follow-up to 48% at 30-year follow-up. Among adolescents who reported dieting, 72% reported dieting again at 21-year follow-up and among those who reported dieting at the 21-year follow-up, 81% reported dieting at 30-year follow-up. Adolescents who overestimated their body weight had threefold higher odds of dieting compared to their counterparts at that age and were more likely to follow persistent dieting patterns into adulthood. After stratifying by BMI categories, normal weight adolescents who overestimated their weight had higher odds of dieting compared with normal weight adolescents who correctly estimated their weight; however, there was no significant association between weight underestimation and dieting behaviour. CONCLUSIONS: The prevalence of dieting behaviour increased from adolescence to adulthood. Adolescent weight overestimation was the most significant factor associated with dieting over the study period. SO WHAT?: Interventions targeting weight misclassification during adolescence may help prevent the adoption of unhealthy dieting behaviours.