Food intake in diabetic rats: isolation of primary metabolic effects of fat feeding.

The effects of varying dietary fat content on food intake and metabolism in streptozotocin-diabetic rats were examined. The metabolic consequences of fat feeding were separated from the marked adjustments in voluntary food consumption that occur when diabetic rats are fed diets containing different amounts of fat by feeding rats a fixed ration of food in which either fats or carbohydrates were reduced by equicaloric amounts, or in which only the concentration of fat, but not other dietary nutrients, was varied systematically. Resulting changes in metabolism and subsequent ad libitum food intake on refeeding were then measured. Rats did not increase their food intake after a prior reduction in carbohydrate consumption but did so after an equicaloric reduction in fat consumption. Urinary glucose excretion during rationing was a function of carbohydrate consumption and was not predictive of changes in food intake during refeeding. The more fat that rats consumed during rationing, the higher their levels of plasma triglycerides and ketone bodies were at the time of refeeding and the less they ate when allowed to eat ad libitum. The orderly changes in food consumption and in plasma triglycerides and ketones observed with variations in fat intake suggest that the effects of fat feeding on food intake in diabetic rats are mediated through the oxidation of ingested fat.