DOI: 10.6084/m9.figshare.30901926.v1
title: Medical progress, relaxed natural selection, and adolescent obesity: implications for global health

description: To examine the role of relaxed natural selection, measured using the Henneberg Index (I<sub>bs</sub>), in influencing adolescent obesity prevalence across 191 countries. Population-level variables, including adolescent obesity prevalence, I<sub>bs</sub> (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. 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. 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. This study explores how improvements in healthcare and living conditions might contribute to rising obesity rates among adolescents worldwide. As modern medicine helps more people survive and have children, natural selection—the process through which harmful genes are gradually reduced in a population—has become weaker. We measured this reduction using the Henneberg Index, which shows how many people in a population live through their full reproductive years. By analyzing data from 191 countries, we found that nations with higher Henneberg Index values, meaning lower natural selection, also have higher rates of adolescent obesity. This relationship remained significant even after accounting for calorie intake, economic development, and urbanization. The findings suggest that genetic factors linked to obesity may be accumulating over generations as a result of medical progress. Recognizing this long-term effect could help improve future obesity prevention strategies that address both biological and environmental factors. The Henneberg Index (Biological State Index) quantifies the degree of reduced natural selection in human populations. This study examined the association between the Henneberg Index and adolescent obesity across 191 countries. Both curvilinear and linear analyses revealed significant positive correlations between the Index and obesity prevalence. The association remained significant after adjusting for calorie intake, GDP, and urbanization. The relationship was stronger in developing than developed countries, indicating greater variability in natural selection and obesity patterns. Findings suggest that reduced natural selection may contribute to obesity prevalence alongside socioeconomic and environmental drivers.