Differences Between Lean and Obese Zucker Rats: The Effect of Poorly Absorbed Dietary Lipid on Energy Intake and Body Weight Gain

Abstract

The effects of substitution of a poorly absorbable dietary lipid (hydrogenated soybean oil) for corn oil (CO) in the diets of lean and obese Zucker rats on food intake, weight gain, serum lipids, and pancreatic lipase activity were observed. During the 24-day study the rats were fed 20% fat diets. The lean female and male Zucker rats compensated for the poorly absorbed dietary hydrogenated soybean oil (HO) by increasing food consumption. By day 6 the lean male Zucker rats had compensated fully. The lean female Zucker rats fed the 20% HO diet also demonstrated compensatory hyperphagia, but adjusted less completely than the males. Both male and female obese Zucker rats fed the HO diet did not compensate for the poorly absorbed dietary lipid by hyperphagia during the first 18 days of the study, and thus consistently absorbed significantly less energy. Obese rats fed HO diets appeared to compensate from day 18 to 24, although this apparent compensation may reflect the decreased food intake of the CO fed rats during this time interval. The consumption of HO diet resulted in increased fecal fat excretion and significant reductions in body weight gain for both lean and obese Zucker rats. Serum lipid and glucose levels were significantly increased in obese rats compared to their lean littermates. Both obese and lean Zucker rats fed the HO diet exhibited decreases in serum triglycerides, cholesterol, phospholipids, and glucose compared to rats fed the CO diet. Pancreatic lipase [EC 3.1.1.3] activities were higher in obese rats compared to lean, and lower in rats fed the HO diet compared to the CO diet.