Effects of equicaloric loads of protein, fat, and carbohydrate on food intake in the rat and man

Two experiments were conducted, one in the rat and one in man, to ascertain the effects of equicaloric loads of protein, fat, carbohydrate, and a mixture of these, on subsequent food intake. Additionally, non-caloric loads were given. In the rat, loads were administered intragastrically, and ad lib food intake was measured after various intervals. Corn-oil loads suppressed food intake less than other equicaloric loads. This suggests that calorie-for-calorie, fat does not suppress intake as much as protein or carbohydrate. Sucrose loads suppressed food intake the most after 1 1 2 hr. Mixture loads had an effect equal to the average of its components after 24-72 hr. In man, loads were given orally after a 13-hr fast. Differences between loads were minimized by suppressing olfaction with noseclips, and taste with topical anesthesia of the mouth. Consumption of test-meal presented 70 min later was measured. Also, various ratings of appetite were made. No differences were found between intakes or ratings after individual loads. But collectively, caloric loads suppressed food intake more than non-caloric loads.