Predictors of Weight Loss in Young Adults

Background: Increased understanding of weight loss among healthy young people in naturalistic settings could inform the development of effective weight control programs. The aim of this study was to describe loss in BMI over 7 years in a population-based sample of healthy young adolescents (mean age 17 years at beginning of follow-up) and identify determinants of BMI loss. Design and Method: Data were available for 681 participants in the Nicotine Dependence in Teens Study (1999-2012), a longitudinal investigation of adolescents in Montreal (Canada). Loss in BMI was assessed between age 17 and 24 years. Potential predictors of BMI loss including age, sex, mother's education, worry about weight, physical activity, screen time, and cigarette smoking were studied in multivariable logistic regression. Results: Males and females gained 2.0 and 1.4 BMI units, respectively, on average, between age 17 and 24 years. However, 9% of males and 14% of females experienced a loss in BMI 1.0 unit. Female sex and a higher BMI at age 17 were associated with a higher probability of BMI loss, but none of age, mother's education, physical activity, screen time, or cigarette smoking were associated with BMI loss between ages 17 and 24. Conclusions: Whereas BMI increased on average between age 17 and 24 years in a population-based sample of healthy young people, 12% of participants experienced a loss in BMI 1 unit. Weight loss was highest among the heaviest persons and did not affect the prevalence of underweight. No single behavior at age 17 stands out as associated with predicting BMI loss.