Abstract
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. Relaxed selection against genes affecting energy balance and metabolism may contribute to the increase of fatness independent from commonly considered positive energy balance. Diagnoses of individual predispositions to obesity at an early age and individual counselling on diet and behaviour may be appropriate strategies to limit further increases in body mass.
Highlights
Obesity prevalence has been increasing though the last several decades worldwide while its causes are not precisely known [1]
Purifying selection plays a role in controlling the mutation load [24,25]. lt may be hypothesised that with the decline in the opportunity for selection there is an increasing quantity of heritable factors altering energy balance and metabolism. These may contribute to increasing numbers of obese individuals, as well as some increase in numbers of too lean individuals, even in situations when environmental factors do not promote increasing adiposity of all members of a population The aim of this paper is to investigate a possible coincidence of the relaxation of natural selection and prevalence of obesity
Regression of obesity prevalence by country on Ibs values per country is an exponential function with the correlation coefficient 0.61 (Fig 2, p
Summary
Obesity prevalence has been increasing though the last several decades worldwide while its causes are not precisely known [1]. This increase is most likely a result of complex interactions between genetic predispositions, environmental factors and human behaviour [2]. People with larger gastrointestinal tracts accumulate more subcutaneous fat [4,5]. Healthy young adult males whose alanine transaminase activity is elevated have greater BMI values [6,7], there is increase in diabetes among young people [8,9] and the increase in diabetes prevalence remains significant.
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