Insulin infusion stimulates daily food intake and body weight gain in diabetic rats.

Current theories state that physiological levels of insulin inhibit daily food intake and reduce body weight. To test whether insulin induces satiety, systematically increasing doses of insulin from 2.0 to 5.0 U/day were infused intravenously into streptozotocin-induced diabetic rats. Food intake increased significantly from 70.0 +/- 1.4 kcal/day during the saline baseline up to 102.2 +/- 1.9 kcal/day in the 3.5 U/day insulin infusion and then stabilized at 95.9 +/- 0.5 kcal/day for the remaining doses (p less than 0.05). Retained energy values (kcal of food intake minus kcal of urinary glucose loss) also increased from 69.9 +/- 1.4 kcal/day to stabilize at 95 kcal/day (p less than 0.001). Food intake and retained energy of normal controls remained unchanged at 75.4 +/- 1.6 kcal/day for the duration of the study. With elevated food intake and retained energy values after the 3.5 U/day insulin dose, the diabetic rats gained more weight than the normal controls (p less than 0.01). Contrary to expectations, increasing the amount of insulin infused through the physiological range results in a 40% increase in daily food intake and a rapid gain in body weight.