Basal hyperinsulinemia in Wistar-rats rendered obese by a high-fat diet

Basal plasma insulin levels were measured in Wistar-rats rendered obese by feeding a high-fat diet (50% fat, w/w). During the period of rapid weight-gaining ("dynamic phase" of the development of obesity) fat-fed rats show elevated basal insulin levels in the peripheral blood plasma. No further enhancement occurred in the so-called "static phase" of obesity. Changing the feeding schedule at 20 weeks of age, e.g. feeding control diets (3% fat, w/v) for 4 weeks to fatty rats, results in a depression of insulin levels to control values together with a reduction of the body weight. The findings are discussed in relation to the dietary induced alterations of carbohydrate and lipid metabolism of obese rats.