Role of genetic factors in childhood obesity and in susceptibility to dietary variations.

The concern about the current epidemic of obesity is heightened by recent data showing an increase in the prevalence of overweight and obesity in children and adolescents. As obese children are at increased risk of becoming obese adults, early identification of individuals at risk of becoming obese is important for the implementation of preventive measures. In that context, it is important to assess the role of genetic and nongenetic factors in childhood obesity as well as in susceptibility to dietary variations. This paper reviews recent data regarding the prevalence of obesity in childhood as well as the role of genetic factors in phenotypes related to obesity, with emphasis on studies conducted on children, when available. The existence of severe cases of obesity, such as those encountered in Mendelian syndromes of obesity or those caused by mutations in single genes, provides strong evidence for a role of genetic factors in the aetiology of childhood obesity. Furthermore, results from family studies suggest that the maximal heritability of obesity phenotypes ranges from about 30% to 50% and that the major affectors of body fat content, energy intake and energy expenditure are also influenced by genetic factors. Finally, there is increasing evidence that responsiveness to dietary intervention is genetically determined.