Insulin binding to monocytes in obese patients treated with carbohydrate restriction and changes in physical activity

Mean [125I]insulin binding to circulating monocytes was low (P less than 0.05 compared to normal controls) in nine obese patients on a weight-maintaining diet in which 45% of the calories were carbohydrate. On a 10% carbohydrate diet, insulin binding was normal in six of seven obese patients. Plasma insulin concentrations were elevated in obese patients on both diets. No correlation was found between insulin binding and plasma insulin concentration. Glucose intolerance and hyperinsulinemia were worsened by keeping the patients at rest and were improved by having the patients walk 3-4 miles/day. The change in physical activity had no effect on [125I]insulin binding to monocytes. We conclude that 1) insulin binding to monocytes in obese patients is generally low in patients on a carbohydrate-rich diet, but is normal in patients on carbohydrate-restricted diets; 2) down-regulation of insulin receptors does not necessarily occur in the presence of hyperinsulinemia: and 3) a walking program results in an improvement in glucose tolerance and hyperinsulinemia that is not associated with a change in insulin binding.