Adolescent BMI: The Importance of Intrinsic and Extrinsic Factors

Objectives: Research shows that overweight adolescents become overweight adults, but do the same factors contribute to weight in adolescence as adulthood? Are extrinsic factors more important than intrinsic characteristics? This study identifies the correlation between BMI and various intrinsic and extrinsic covariates and evaluates their relative importance in BMI determination. Furthermore, it separates the sample into adolescents (12-20) and adults (21+) and compares the primary determinants of BMI between the two groups.

Methods: Using 15 years of panel data, multi-level change models including both fixed and random effects assess the impact of extrinsic—environmental, biological, geographic and household—and intrinsic—sexual activity, substance use, desire to lose weight, etc.—characteristics on BMI. Separate adolescent and adult samples test for differences in relative BMI determinants.

Results: Results suggest that race and age are the most significant determinants of BMI at all ages. However, other determinants differ between adolescents are adults. In the early years of adolescents, intrinsic factors are highly deterministic, while extrinsic factors are insignificant. Intrinsic determinates of significance include age of first sexual encounter, tobacco experimentation, perspective on general health and desire to lose/stay the same weight play a significant role for adolescents. As youth age into adults, intrinsic factors decrease in importance, while extrinsic covariates become more deterministic.

Conclusion: While biological/genetic attributes, are the largest determinants of BMI at every age, intrinsic factors appear to be more significant than extrinsic characteristics during adolescents. As individuals age, intrinsic determinants decrease in importance as extrinsic characteristics increase in significance. Thus, the weight determinants differ between adolescents and adults suggesting different methods of policy intervention be used to improve the health of both groups.