Genetic aspects of body composition

Body composition is reviewed as a composite of several traits each with the ir distinctive genetic basis, including major effects of genes at single lo ci. Studies involving twins, adopted offspring, and other family relatives have demonstrated the high heritability (0.4-0.7) of many of the traits inv olved. Genotype-environment interactions with diet and activity occur in do mesticated animals and humans and associations with voluntary choice of die t and level of activity are unfavorable. Body composition is the main refer ence for a normal homeostatic mechanism involving appetite and energy expen diture control. Identification of major genes controlling products, such as leptin, indicate mechanisms for this control and its manifestations in lea nness and obesity. The plasticity of certain aspects of body composition ca n be exploited by livestock breeders, although the side effects are unpredi ctable. They also promise the possibility of gene therapy in these hitherto intractable conditions. Novel major genes that are being rapidly uncovered in many species may enable future deployment of gene therapy. The control of body composition is likely to remain a challenge because of the unfavora ble genetic correlations and the failure of ordinary, fallible humans to th wart the complex genetically programmed destiny they have inherited. (C) El sevier Science Inc.