Behavioral components of high-fat diet hyperphagia: meal size and postprandial satiety

Previously, rats fed a high-fat liquid diet (HF) ad libitum consumed more k ilocalories and had greater weight gain than rats fed a liquid high-carbohy drate diet (HC) of equivalent energy density (Warwick, Z. S., and H. P. Wei ngarten. Am. J. Physiol. Regulatory Integrative Comp. Physiol. 269: R30-R37 , 1995). The present series of experiments sought to clarify the behavioral expression of KF hyperphagia by comparing HF and HC with regard to meal si ze and magnitude of postingestive satiety effect. Meal size of HF was great er than HC at 2.3 kcal/ml and also when diets were formulated at 1.15 kcal/ ml. In a preload-test meal paradigm, an orally consumed HF preload was less satiating than a calorically equivalent HC preload across a range of prelo ad volumes and intermeal intervals. Sensory-specific satiety was ruled out as an explanation of the relatively greater intake of test meal after an HF preload meal; an intragastrically delivered KF preload was less satiating than intragastric HC. Furthermore, a fat (corn oil emulsion) preload was le ss satiating than a carbohydrate (sucrose) preload when an evaporated milk test meal was used. These findings indicate that hyperphagia an an HF diet is expressed in increased meal size and decreased intermeal interval.