Energy expenditure and requirements in aging humans.

Although physical activity is frequently recommended for the elderly individual, its influence on energy intake and energy expenditure is unclear. The use of indirect calorimetry techniques and stable isotopes make it possible to examine the effects of physical activity on total daily energy expenditure and its components. In this review, the influence of physical activity on adaptive changes in energy intake, daily energy expenditure, resting metabolic rate and the energy expenditure of physical activity during nonexercising time was examined. Recent findings show that moderate physical activity can increase resting metabolic rate and energy intake in the elderly. Vigorous exercise, however, did not increase total daily energy expenditure because of a compensatory decline in physical activity during nonexercising time. These findings should prompt investigators to re-examine the influence of different levels of endurance exercise on total daily energy expenditure in an attempt to maximize the energy expending properties of physical exercise in older persons. A second objective was to examine the current status of methodology to predict energy requirements in older persons. Current recommendations for energy lack specificity and have not considered the influence of physical activity and body composition. Energy needs of older persons need to be re-examined based on the measurement of total daily energy expenditure. It will then be important to identify biological markers of total daily energy expenditure that take into account the variation in physical activity and body composition.