Adolescent BMI: The Importance of Intrinsic and Extrinsic Factors

Abstract

Objectives: Research shows that weight trends in adolescence persist into adulthood, but do the same factors contribute to weight in adolescence as in adulthood? Are extrinsic factors presumably more important than intrinsic characteristics? This study identifies the correlation between BMI and various intrinsic and extrinsic factors and evaluates their relative importance in BMI development. It compares the primary determinants for adolescents (12-20 years old) and adults (21+ years old). Methods: Using 15 years of panel data, generalized linear models, we assessed the impact of extrinsic-environmental, biological, geographic and household-and intrinsic-sexual activity, substance use, desire to lose weight, etc.-characteristics on adolescent and adult BMI. Multinomial logit models tested the contribution of these characteristics to weight categories. Results: Race and age were the most significant BMI correlates at all ages. This remains true for weight classification as well. For young adolescents, intrinsic factors are highly deterministic, while extrinsic factors play no role. As adolescents age into adults, intrinsic factors continue to be deterministic, while extrinsic covariates also emerge as deterministic. Intrinsic determinates of significance include age of first sexual encounter, tobacco experimentation, perspective on general health, and desire to lose weight (or stay the same weight). Conclusion: While biological/genetic attributes are the largest determinants of BMI at every age, intrinsic factors play a larger role in adolescent BMI development than adults. As individuals age, intrinsic determinants remain important, but extrinsic characteristics contribute significantly to weight classification. Thus, the weight determinants differ between adolescents and adults suggesting different methods of policy intervention be used for adolescents and adults.