Predictors of adolescents' weight misclassification: A longitudinal study

Objective: To examine adolescents' and mothers' misclassification of the adolescents' body weight and associated early life predictors.

Methods: Data are from a sample of women and their children who were part of a longitudinal Australian birth cohort study. We analysed data of 3925 adolescents, 3721 mothers, and 2593 mother-offspring pairs. At the 14-year follow up, we derived adolescents' body weight category (underweight, normal or overweight) based on their measured height and weight and adolescents reported their similar subjective weight categories. Similarly, mothers reported perceived weight of their adolescents' offspring. We compared objectively measured weight with subjective weight perceptions to identify misclassifications. Possible predictors of weight misclassification were taken from pregnancy, childhood and the adolescent period.

Results: Almost a third of adolescents and a quarter of mothers misclassified the adolescents' body weight. Underestimation was observed more often in overweight adolescents. Overestimation was observed more often in underweight adolescents. More than a third of underweight adolescents and almost half of mothers of underweight children overestimated the adolescent's body weight. Normal weight females overestimated their body weight more than their males' counterparts. Predictor of misclassification included being female; dieting to lose weight; having over or underweight mothers; and having high level of poor mental health.

Conclusions: Findings of this study suggest that adolescent weight misclassification is common across all BMI categories. Being female, dieting to lose weight, poor mental health and maternal BMI status predict misclassification. Further studies are needed to evaluate the population health significance of weight misclassifications.