title: Enhanced flavor-nutrient conditioning in obese rats on a high-fat, high-carbohydrate choice diet.
abstract: Through flavor-nutrient conditioning rats learn to prefer and increase their intake of flavors paired with rewarding, postingestive nutritional consequences. Since obesity is linked to altered experience of food reward and to perturbations of nutrient sensing, we investigated flavor-nutrient learning in rats made obese using a high fat/high carbohydrate (HFHC) choice model of diet-induced obesity (ad libitum lard and maltodextrin solution plus standard rodent chow). Forty rats were maintained on HFHC to induce substantial weight gain, and 20 were maintained on chow only (CON). Among HFHC rats, individual differences in propensity to weight gain were studied by comparing those with the highest proportional weight gain (obesity prone, OP) to those with the lowest (obesity resistant, OR). Sensitivity to postingestive food reward was tested in a flavor-nutrient conditioning protocol. To measure initial, within-meal stimulation of flavor acceptance by post-oral nutrient sensing, first, in sessions 1-3, baseline licking was measured while rats consumed grape- or cherry-flavored saccharin accompanied by intragastric (IG) water infusion. Then, in the next three test sessions they received the opposite flavor paired with 5 ml of IG 12% glucose. Finally, after additional sessions alternating between the two flavor-infusion contingencies, preference was measured in a two-bottle choice between the flavors without IG infusions. HFHC-OP rats showed stronger initial enhancement of intake in the first glucose infusion sessions than CON or HFHC-OR rats. OP rats also most strongly preferred the glucose-paired flavor in the two-bottle choice. These differences between OP versus OR and CON rats suggest that obesity is linked to responsiveness to postoral nutrient reward, consistent with the view that flavor-nutrient learning perpetuates overeating in obesity.
authors.affiliation: Program in Neuroscience, Bucknell University, Lewisburg, PA, USA.
authors.forename: Hallie S
authors.initials: HS
authors.lastname: Wald
authors.affiliation: Department of Psychology, Bucknell University, Lewisburg, PA, USA; Program in Neuroscience, Bucknell University, Lewisburg, PA, USA; Program in Animal Behavior, Bucknell University, Lewisburg, PA, USA. Electronic address: kmyers@bucknell.edu.
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Myers
mesh_terms: D000821:Animal Feed / Q000009:adverse effects; D000818:Animals; D002755:Choice Behavior / Q000502:physiology; D003213:Conditioning, Psychological / Q000502:physiology; D059305:Diet, High-Fat / Q000009:adverse effects; D004041:Dietary Fats / Q000009:adverse effects; D004195:Disease Models, Animal; D060766:Drinking Water / Q000008:administration & dosage; D005260:Female; D005421:Flavoring Agents; D005518:Food Preferences / Q000502:physiology; D005947:Glucose / Q000008:administration & dosage; D009043:Motor Activity / Q000502:physiology; D009765:Obesity / Q000503:physiopathology / Q000523:psychology*; D011134:Polysaccharides / Q000009:adverse effects; D011897:Random Allocation; D017207:Rats, Sprague-Dawley; D012201:Reward; D012439:Saccharin
chemical_list: D004041:Dietary Fats; D060766:Drinking Water; D005421:Flavoring Agents; D011134:Polysaccharides; C008315:maltodextrin; D012439:Saccharin; D005947:Glucose; C029310:lard
keywords: Appetition; Flavor–nutrient conditioning; Food preferences; Food reward; Learning; Obesity