Medical progress, relaxed natural selection, and adolescent obesity: implications for global health.

Objective: To examine the role of relaxed natural selection, measured using the Henneberg Index (I_bs), in influencing adolescent obesity prevalence across 191 countries.

Methods: Population-level variables, including adolescent obesity prevalence, I_bs (Henneberg Index), GDP PPP, urbanization, and calorie intake, were obtained from United Nations sources. The relationship between the Henneberg Index and adolescent obesity was analyzed using curvilinear and linear regression models with raw and log-transformed data to address non-homoscedasticity. Regional correlations were explored by grouping countries.

Results: A significant correlation (r∼0.5) between the Henneberg Index and adolescent obesity was found and remained consistent through third-order polynomial regression and partial correlations after adjusting for GDP PPP, urbanization, and calorie intake. The correlation was stronger in developing countries compared to developed ones. Stepwise multiple regression analysis identified the Henneberg Index as the second most significant predictor of adolescent obesity, following GDP PPP. Calorie intake did not significantly predict adolescent obesity in the models.

Conclusions: Reduced natural selection, facilitated by medical practices allowing individuals with obesity-linked traits to reproduce, may contribute to the population-level accumulation of these traits, increasing adolescent obesity. These findings underscore the need to consider evolutionary and genetic factors alongside environmental and socioeconomic determinants in developing obesity prevention strategies.