Relationship of physical activity, glucose tolerance, and weight management.

Diabetes mellitus and hyperinsulinemia have been demonstrated by population studies to be risk factors for ischemic heart disease (IHD). But, the relationship of glucose intolerance to IHD is still unclear. Restricted physical activity and obesity both result experimentally in glucose intolerance and cell insulin insensitivity with hyperinsulinemia and may contribute to IHD. Prolonged moderate-intensity exercise lowers plasma insulin levels in obese hyperinsulinemic subjects as well as in nonobese subjects. Increased insulin binding to cell receptors (and number of insulin receptors) and a decrease in insulin secretion from the pancreas are believed to be contributing mechanisms. The independent effect of exercise on glucose tolerance is less clear, although there are strong indications favoring the positive effects of physical activity. There is also suggestive evidence that exercise may be beneficial in improving metabolic control in type II diabetes. Regular exercise together with appropriate diet and correction of obesity seems to be a more promising approach to improving glucose tolerance and controlling diabetes than does exercise alone.