Studies of identical twins at the Universite Laval in Quebec, Canada, have produced evidence to confirm the role of genes in obesity. Twelve pairs of young adult male identical twins were overfed by 1,000kcal a day, six days a week for 100 days - making a total overfeed of 84,000kcal.
The similarity within each pair was significant in terms of body weight gain and percentage body fat, with three times more variance among pairs than within pairs. When it came to regional fat distribution, the differences were even more striking, with six times as much variance among pairs as within them.