Influence of age and endurance training on metabolic rate and hormones in healthy men

The associations among age, maximal aerobic capacity (VO2max), and body composition with resting metabolic rate (RMR), and fasting plasma hormones were examined in endurance-trained and untrained older and younger men. A higher RMR (approximately 6%; P less than 0.05), normalized per kilogram of fat-free weight (FFW), was found in endurance-trained younger and older men relative to untrained men. VO2max, independent of FFW, accounted for a significant portion of the variation in RMR. Fasting insulin and the fasting insulin-to-glucose ratio were higher in older men relative to younger men. This difference was diminished when differences in percent body fat were taken into account. Plasma thyroid hormones and glucagon were not associated with age, VO2max, or percent body fat. We conclude that endurance-trained and older men have a higher RMR than untrained younger and older men that is independent of differences in FFW. Plasma levels of thyroid hormones and glucagon are not influenced by age, VO2max, or adiposity in healthy nonobese men.