title: Independent effects of diet palatability and fat content on bout size and daily intake in rats.
abstract: Although considerable evidence attests to the hyperphagic effects of high-fat (HF) diets, the attribute(s) of these diets (e.g., palatability, caloric density, and postingestive effects) which promote overeating is still unclear. The present studies investigated the independent effects of diet palatability and macronutrient composition on intake using the self-regulated intragastric infusion paradigm. In Experiment 1, rats were infused with either HF or high-carbohydrate (HC) diet while drinking either saccharin (Sacc) or a more palatable saccharin-glucose (SaccGlu) test solution for 9 days. HF elicited greater daily intake than HC; lick pattern analysis revealed that HF produced larger but not more frequent bouts. Test solution was not related to intake, possibly due to the relatively modest palatability manipulation. Experiment 2 provided a more sensitive test: The palatability manipulation was strengthened and diet infusion made optional by provision of chow. HF again elicited larger bout size and total daily intake (diet+chow) than HC. Rats given the more palatable solution significantly increased intake (via larger bouts) and thus the amount of diet infused, but chow intake decreased such that total kilocalorie intake was not significantly related to solution palatability. The reliable observation that HF promoted larger bout size and greater total kilocalorie intake than HC provides additional evidence that fat sends weaker feedback signals relevant to controls of both satiation (suppression of ongoing eating, behaviorally manifest in meal size) and satiety (suppression of subsequent intake, reflected in total daily intake).
authors.affiliation: Department of Psychology, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA. warwick@umbc.edu
authors.forename: Zoe S
authors.initials: ZS
authors.lastname: Warwick
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Synowski
authors.forename: Karmeshia D
authors.initials: KD
authors.lastname: Rice
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Smart
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001069:Appetite Regulation; D001522:Behavior, Animal; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage* / Q000494:pharmacology; D004326:Drinking; D004327:Drinking Behavior / Q000187:drug effects* / Q000502:physiology; D004435:Eating / Q000187:drug effects* / Q000502:physiology; D002149:Energy Intake; D005247:Feeding Behavior / Q000187:drug effects* / Q000502:physiology; D005518:Food Preferences / Q000502:physiology*; D005947:Glucose; D008297:Male; D011897:Random Allocation; D051381:Rats; D020318:Rats, Long-Evans; D012439:Saccharin; D012646:Self Administration / Q000379:methods; D013997:Time Factors
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D012439:Saccharin; D005947:Glucose