GENETIC INFLUENCES ON ENERGY-EXPENDITURE IN HUMANS

Variations in human energy expenditure are partly because of an influence of the genotype, even after control for the well-established concomitants of energy expenditure. Using the techniques of genetic epidemiology, we have found that about 40% of the variance in resting metabolic rate, thermic effect of food, and energy cost of low-to-moderate intensity exercise (less-than-or-equal-to 5 times the resting metabolic rate) is explained by inherited characteristics. A significant genetic effect has also been reported for the level of habitual physical activity. The existence of a genotype-environment interaction has also been investigated. Thus, in response to chronic overfeeding, as well as negative energy balance, changes in the components of energy expenditure exhibit significant identical twin pair resemblance. Nutrient partitioning is emerging as a major determinant of the individual differences in metabolic rate responses to overfeeding or negative energy balance conditions. Taken as a whole, these observations consistently support the hypothesis that heredity plays a significant role in the various components of energy expenditure in humans.