Effects of training on weight, food intake, and body composition in aging rats.

This study investigated the effect of endurance training on body weight, food intake, and body composition in female rats age 6, 15, and 27 mo. Animals underwent 12 wk of treadmill running. There was a significant increase in percent body fat associated with age. Training induced significant reductions in body fat which were of the same relative magnitude in all age groups. The 6-mo and 15-mo exercising rats significantly increased their food intake in response to the training stimulus; the 27-mo trained animals were unable to increase their food consumption relative to controls. It was concluded that 27-mo old animals are capable of changes in body composition similar to those of their younger counterparts, however, physiological mechanisms responsible for these shifts are age dependent. Older animals do not compensate their dietary intake for the increased energy expenditure of exercise as do the younger animals.