Worldwide increase of obesity is related to the reduced opportunity for natural selection

Worldwide rise of obesity may be partly related to the relaxation of natural selection in the last few generations. Accumulation of mutations affecting metabolism towards excessive fat deposition is suggested to be a result of less purging selection. Using the WHO and UN data for 159 countries there is a significant correlation (r = 0.60, p<0.01) between an index of the relaxed opportunity for selection (Biological State Index) and prevalence of obesity (percentage of individuals with BMI >30kg/m2). This correlation remains significant (r = 0.32., p<0.01) when caloric intake and insufficient physical activity prevalence are kept statistically constant (partial correlation analysis, N = 82). The correlation is still significant when gross domestic product per capita is also kept constant (r = 0.24, p <0.05, N = 81). In the last decades, prevalence of both obesity and underweight has increased in some countries despite no change in caloric intake nor in physical inactivity prevalence.

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