Dietary Fat Dose Dependently Increases Spontaneous Caloric Intake in Rat

Abstract

To characterize the dose-response relationship between dietary fat to carbohydrate ratio and spontaneous caloric intake. Male Long-Evans rats consumed milk-based liquid diets that differed in fat content (17% to 60% of kilocalories) but had equivalent protein content and energy density. In Experiment 1, rats consumed one of the diets (n = 9/diet group) as the sole source of nutrition for 16 days. In Experiment 2, diets were offered as an option to nutritionally complete chow for 4 days followed by a 3-day chow-only washout in a randomized within-subjects design (n = 30). In Experiment 3, nine rats received isocaloric intragastric infusions of diet overnight, with chow available ad libitum. At least two no-infusion days separated the different diet infusions, which were given in random order. Food intake was measured daily Dietary fat dose dependently increased total daily kilocalories in each of the three paradigms. These data imply that the postingestive effects of carbohydrate and fat differentially engage the physiological substrates that regulate daily caloric intake. These findings reiterate the importance of investigating macronutrient-specific controls of feeding, rather than prematurely concluding that dietary attributes that covary with fat content (e.g., caloric density and palatability) drive the overeating associated with a high-fat diet.