Insulin counteracts the satiating effect of a fat meal in rats

The effects of insulin administration of the reduction on food intake which follows a meal of corn oil was examined in normal and streptozotocin-diabetic rats. In the first experiment, a single injection of long-acting, protamine zinc insulin (3 IU) curtailed the decrease in 24-hr food intake that occurred in normal and diabetic rats after ingestion of 2.0 ml of oil. In a second experiment, injection of short-acting, regular insulin (0.5 IU) prevented the depression of food intake which occurred 6-24 hr after ingestion of 1.5 ml of corn oil, but not at earlier time intervals. In a third experiment, the short-term suppression of food intake in diabetic rats that occurred within 6 hr after a 1.5 ml meal of oil was reduced by chronic administration of insulin (3 IU/day) via a subcutaneously implanted osmotic pump. The results indicate that a relatively long-lasting effect of insulin counteracts the satiation from ingested fat and suggest that insulin's role in the control of food intake may depend on the composition of the diet.