European Lactase Persistence Allele is Associated With Increase in Body Mass Index
J. A. Kettunen et al.
The global prevalence of obesity, usually indexed by body mass index (BMI) cut-offs, has increased significantly in the recent decades, mainly due to positive energy balance. However, the impact of a selection for specific genes cannot be excluded. Here we have tested the association between BMI and one of the best known genetic variants showing strong selective pressure: the functional variant in the cis-regulatory element of the lactase gene. We tested this variant since it is presumed to provide nutritional advantage in specific physical and cultural environments. We found that the variant responsible for lactase persistence among Europeans was also associated with higher BMI in a Nordic population sample (p = 1.3*10-5) of 15 209 individuals, the size of the effect being close to that of FTO. We tested the effect of population stratification and concluded that the association was not due to population substructure.
The mutation which results in lactase persistence is one of the canonical examples of recent human evolution driven by natural selection. It looks as if over the past 10,000 years several populations have developed this trait independently due to selective pressures, in particular the nutritional benefit of adult digestion of the lactose sugars in milk. The fact that in northern European populations where ~95% of people are lactase persistent there is a difference in body mass which tracks this trait is intriguing, as it suggests the reasons why this new ability was driven to fixation so powerfully. In the pre-modern world extra caloric intake would probably have been a difference between life and death, and body fat has also been related to female fertility.