Somatic, endocrine, and serum lipid changes during detraining in adult hamsters.

Effects of abrupt discontinuation of chronic exercise on body composition and serum lipid, insulin, and glucagon concentrations were examined in adult female hamsters. Thirty-six hamsters (100 to 120 g) were randomly allotted to two groups of 18 each for an 84-day study. One group served as controls and were sedentary throughout the experimental period; another group had access to voluntary running on horizontal discs during the first 42 days of the experimental period. Six hamsters from each group were killed at the end of the exercise period and at 12 and 42 days after retirement. Results showed that hamsters engaged in high levels of voluntary activity increased food intake by about 10 to 20% and this effect persisted for about 10 days after retirement. Voluntary running resulted in a 60% reduction in body fat content and a 30% decrease in serum triglyceride levels. Exercise was also associated with an increase in body cholesterol level, a decrease in glucagon concentration, and a suggestive increase in serum insulin level. Increased food consumption and changes in serum insulin and glucagon may reflect compensatory adjustments to increased energy expenditure of exercise. Discontinuation of exercise resulted in a reversal of exercise effects on body fat, body cholesterol, and serum triglyceride levels.