Regulation of energy expenditure in aging humans.

A brief overview of the effects of aging on two components of energy expenditure, RMR and TEF, has been presented. Whereas the decline in RMR appears to be related primarily to the loss of muscle tissue, the reason for the lower TEF in older individuals is less clear. Evidence has been provided suggesting that physical activity influences RMR and TEF in younger and older individuals. The possibility is raised that regular physical activity will increase RMR and TEF in older individuals. The increase in resting energy expenditure (RMR and TEF), in addition to the direct energy cost of physical exercise, may help increase the total energy requirements in older individuals. The majority of studies support an increase in resting SNSA in older individuals. The level of physical activity and percentage of body fat may be two factors contributing to age-related alterations in resting sympathetic tone. Future studies should continue to examine the effects of physical activity and body composition on metabolic rate and SNSA in older individuals.