[Genetics and obesity in man].

This brief review constitutes a synthesis of some of the research conducted in our laboratory about the role of inheritance in human variation observed for subcutaneous fat, total fat mass and subcutaneous fat distribution. Our first studies were of the genetic epidemiology type and were conducted on a cohort of 1,698 subjects from 409 families of French descent living in the greater Québec city area. These studies have shown that heritability of the amount of subcutaneous fat was almost zero, while the additive genetic effect reached about 25% of human variation, after statistical control over the effects of age and gender, for total fat mass and regional subcutaneous fat distribution. On the other hand, there are considerable individual differences in the response to overfeeding and those that pertain to body weight and body composition, and the various components of daily energy expenditure in subjects kept inactive, are mainly determined by the genotype. These findings come from a study on the response to chronic overfeeding, sustained for 22 consecutive days, undertaken with 6 pairs of identical twins. In general, our research shows that there are individuals who are more at risk of becoming obese because of undetermined genetic characteristics but that are apparently associated somehow with the various components of habitual energy expenditure.