Genetic effects in human energy expenditure components.

It is increasingly recognized that variations in human energy expenditure are partly due to an influence of the genotype, even after control for the well established concomitants of energy expenditure. Using the technique of genetic epidemiology, we have found that about 40 percent 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, we have demonstrated that in response to chronic overfeeding, as well as negative energy balance, changes in the components of energy expenditure are partly determined by one's genotype. Taken as a whole, these observations consistently support the hypothesis that heredity plays a significant role on the variations in the various components of energy expenditure in humans. Further research should now be focused more on the identification of biochemical and molecular markers of these energy expenditure characteristics.