HIGH-FAT DIET PREFERENCE AND OVEREATING MEDIATED BY POSTINGESTIVE FACTORS IN RATS

The role of postingestive factors in the preference for and overconsum ption of high-fat (HF) foods, relative to high-carbohydrate (HC) foods , was investigated using a self-regulated intragastric feeding procedu re. On one-bottle training days, rats drank one flavored saccharin sol ution [conditioned stimulus (CS) + HF] paired with intragastric infusi ons of an HF liquid diet, a second flavored solution (CSI-HC) paired w ith an HC liquid diet, and a third flavored solution (CS-) paired with intragastric water. The diets had the same energy and protein content ; the CS solutions and infusions along with chow were available ad Lib itum. The rats drank more CS and self-infused more diet on HF than HC training days. In two-bottle choice tests, the rats preferred the CS+H F to the CS+HC and both CS+HF and CS+HC to the CS-. The rats consumed more CS+HF than CS+HC by taking more bouts per day; bout sizes did not reliably differ. In a subsequent experiment, rats preferred the CS+HF even though diet intakes in training were matched. In a final experim ent, the CS+HC and CS+HF intakes were equated in training by diluting the HC diet. Now the rats did not reliably prefer the CS+HF to the CSHC, yet caloric intakes were much higher on CS+HF than CS+HC training days. Thus, relative to an isocaloric HC diet, the postingestive effec ts of HF diets stimulate overeating and condition a stronger flavor pr eference. Reduced satiety rather than increased reinforcement may be t he direct promoter of overeating. However, postingestive reinforcement may enhance the selection of HF foods when a choice of HF and HC food s is available.