Loss of skeletal muscle mass with aging: effect on glucose tolerance.

It is generally believed that aging results in glucose intolerance. Since skeletal muscle is the major site of glucose uptake following an oral glucose tolerance test (OGTT), it is reasonable to hypothesize that loss of muscle mass with aging causes glucose intolerance. Evidence against this concept comes from extensive data demonstrating the usefulness of the recommended procedures for performing an OGTT. This involves giving 75 g of glucose to all subjects regardless of body weight, and the criteria for categorizing glucose intolerance are the same for all individuals. That this works well, with no evidence that larger people have better glucose tolerance than smaller people, suggests that muscle mass does not usually play a role. Recent studies on humans and rats indicate that aging per se does not result in glucose intolerance. In most of those older people with decreased glucose tolerance, this problem appears to be due to accumulation of abdominal fat with development of insulin resistance. We conclude that the loss of muscle mass with aging does not usually result in glucose intolerance.