Learned suppression of intake based on anticipated calories: cross-nutrient comparisons.
Following training with distinctively flavored solutions which differ in calories and thus in their postingestive effects, rats demonstrate flavor-postingestive consequence learning by preferentially consuming one of the flavors in two-bottle tests (both flavors presented in nutrient-identical solutions). The direction of the preference--for the flavor previously paired with more calories (F-hi) or for the flavor previously paired with fewer calories (F-lo)--depends critically upon the magnitude of postingestive effects experienced during training. The most frequent and more thoroughly investigated observation has been preferential consumption of F-hi (conditioned flavor preference). However, when relatively concentrated solutions (e.g., 5% and 30% sucrose) are used as the training nutrients, F-lo is preferentially consumed in two-bottle tests. This lesser intake of F-hi presumably reflects its previous association with the more potent satiating effect of the highly concentrated nutrient: conditioned satiety. The present series of experiments explored conditioned satiety across nutrient types. In each experiment, rats consumed 30 mL of distinctively flavored nutritive solution per day, alternating between a distinctively flavored high-calorie (1.6 kcal/mL) solution and a lower calorie (0.2 kcal/mL) solution containing a different flavor. Two-bottle testing evaluated whether conditioned satiety was evident. Experiment 1 found that rats trained with sucrose, fructose, glucose, maltodextrin, or saccharin-sweetened medium-chain triglyceride oil emulsion preferentially consumed F-lo in two-bottle tests. In contrast, rats trained with corn oil emulsions tended to preferentially consume F-hi. In Experiment 2, increasing the number of corn oil calories associated with F-hi produced a tendency toward preferential intake of F-lo in two-bottle tests. In Experiment 3, rats consumed a high-fat maintenance diet; sucrose-trained rats again consumed more F-lo than F-hi, whereas rats trained with corn oil emulsions showed a tendency (nonsignificant) to consume more F-lo in two-bottle tests. In Experiment 4, however, adding saccharin to corn oil emulsions did produce conditioned satiety. These findings demonstrate conditioned satiety as a robust phenomenon across various nutrient types; however, corn oil calories entrain conditioned satiety only under certain conditions.
Warwick
Z S
ZS
Department of Psychology, University of Maryland Baltimore County, Baltimore 21250, USA.
Bowen
K J
KJ
Synowski
S J
SJ
D000818:Animals; D003216:Conditioning, Operant / Q000502:physiology*; D003314:Corn Oil; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004041:Dietary Fats / Q000494:pharmacology; D004435:Eating / Q000523:psychology*; D002149:Energy Intake / Q000502:physiology*; D005502:Food; D008297:Male; D051381:Rats; D012528:Satiety Response / Q000502:physiology*; D013649:Taste / Q000187:drug effects / Q000502:physiology
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D003314:Corn Oil