Energy density and macronutrient composition determine flavor preference conditioned by intragastric infusions of mixed diets.
ABSTRACT In prior studies rats preferred a flavor (CS+HF) paired with intragastric (IG) infusions of a high-fat diet to a flavor (CS+HC) paired with a high-carbohydrate diet, yet just the opposite preference was observed with pure-nutrient infusions. The present study tested the hypothesis that variations in nutrient density as well as composition influence flavor learning. Animals were trained (22 h/day) with IG infusion of milk-based high-fat and high-carbohydrate liquid diets paired with intakes of flavored, noncaloric CS+ solutions. A third flavor, the CS-, was paired with water infusion. Standard chow was available ad libitum. The rats preferred both CS+ flavors to the CS-, whether the infused diets were dense (HF and HC, 2.1 kcal/ml) or dilute (hf and hc, 0.5 kcal/ml), indicating that all diet infusions were reinforcing. They consumed the CS+hc and CS+hf equally in training, and preferred the CS+hc, showing that at low-energy density carbohydrate was more reinforcing than fat. In contrast, CS+HF intake exceeded that of CS+HC in training, and the rats preferred the CS+HF to the CS+HC. In further tests the rats preferred the CS+HF to the CS+hc, the CS+HF to the CS+hf, and the CS+HC to the CS+hc; i.e., when the diets differed in energy density the flavors associated with the more concentrated infusions were preferred. In the absence of influence by flavor cues from the nutrients themselves, rats' preferences for flavors associated with diets high in fat or carbohydrate are dependent on energy density. The differential satiating effects of fat and carbohydrate may contribute to these density-dependent preferences.
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ABSTRACT: A growing body of laboratory-based, clinical, and epidemiological data suggests that low-energy-dense diets are associated with better diet quality, lower energy intakes, and body weight. Dietary energy density can be lowered by adding water-rich fruits, vegetables, cooked grains, and soups to the diet, and by reducing the diet's fat content. Low-energy-dense diets can be successfully incorporated into clinical dietetics since they help lower energy intake without reducing food volume and thus help individuals avoid feeling hungry and deprived. There are multiple steps that could be taken by nutrition professionals and food manufacturers to encourage the consumption of low-energy-dense diets. The goal is to develop reduced-calorie eating plans that meet personal food preferences and also provide satisfying food portions. Since using energy density to guide food choices leads to food patterns consistent with dietary guidelines, policy level initiatives should be devised to help ensure that low-energy-dense diets are affordable and accessible to all.Journal of the American Dietetic Association 06/2005; 105(5 Suppl 1):S98-103. · 3.80 Impact Factor
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ABSTRACT: A series of studies in rat using isoenergetic (kcal/ml) liquid diets differing in fat content has previously found dietary fat to dose-dependently increase daily caloric intake. In single-meal tests in which meal initiation was externally evoked in feeding-associated environments, the behavioral expression of this overeating was found to be larger meal intake. The present studies confirmed the ecological validity of this larger meal size of high-fat diet (HF) relative to high-carbohydrate diet (HC): meal size of HF>HC in home-cage testing (Experiment 1), and during undisturbed, spontaneous feeding in which ingestive behavior was continuously monitored (Experiments 2 and 3). These findings demonstrate that single-meal paradigms yield results consistent with spontaneous feeding of high-fat and high-carbohydrate liquid diets, thus supporting the use of single-meal studies to better understand the physiological bases of elevated caloric intake associated with chronic consumption of a high-fat diet.Appetite 10/2005; 45(2):191-4. · 2.54 Impact Factor
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ABSTRACT: Nutrient-conditioned flavor preferences have been obtained with a variety of procedures, but one study indicates that rats do not readily learn to prefer the flavor of real-fed food to the flavor of sham-fed food. This issue was reexamined in food-deprived rats trained to real feed (gastric fistula closed) and sham feed (gastric fistula open) different flavored Polycose solutions (cherry or grape). Sham-feeding intakes in the one-bottle training sessions (30 min) were limited to the amount consumed in real-feeding sessions; intakes were not limited during two-bottle preference tests (10 min). In Experiment 1, when tested with 32% Polycose solutions, the animals tended to prefer the sham-fed Polycose to the real-fed Polycose. When subsequently trained and tested with 8% Polycose solutions, the same animals displayed a strong preference (approximately 90%) for the real-fed Polycose. These findings were confirmed in Experiment 2 using separate groups. Rats trained with 8% Polycose readily learned to prefer the real-fed solution, and rats trained with 32% Polycose initially preferred the sham-fed Polycose solution. With additional training the 32% Polycose group developed a preference for the real-fed solution. In experiment 3, rats trained to real feed flavored 8% and 32% Polycose solutions developed strong preferences for the 32% solution. This finding suggests that the tendency to prefer sham-fed to real-fed 32% Polycose is not due to aversive postingestive effects of the real-fed solution. Taken together, the results indicate that Polycose has a postingestive positive reinforcing effect that can be revealed using the sham-feeding preparation.(ABSTRACT TRUNCATED AT 250 WORDS)Physiology & Behavior 09/1994; 56(2):331-7. · 3.16 Impact Factor