The genetics of obesity: practical implications

Over the past years substantial progress has been made in the molecular elu cidation of monogenic forms of obesity both in rodents and in humans. In ad dition, several quantitive trait loci have been mapped in mice. in humans, non-parametric linkage studies have led to the identification of relevant c hromosomal regions, some of which have already been confirmed. in this revi ew we focus on an interpretation of the heritability estimates obtained in twin, family and adoption studies. These estimates include both direct and indirect genetic effects. Nan-additive genetic factors seemingly contribute even more than additive factors. The importance of the non-shared environm ent is stressed. Gene x gene interactions need to be considered when interp reting recent molecular genetic results pertaining to haplo-insufficiency m utations in the melanocortin-4 receptor gene. We conclude by discussing the implications of the recent molecular findings in humans for phenotypical a ssessment in ongoing family studies.