Hedonic Hunger: a New Dimension of Appetite? ⁎ Michael R
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Physiology & Behavior 91 (2007) 432–439 Hedonic hunger: A new dimension of appetite? ⁎ Michael R. Lowe , Meghan L. Butryn Department of Psychology, Drexel University, Philadelphia, PA 19102, USA Abstract An increasing proportion of human food consumption appears to be driven by pleasure, not just by the need for calories. In addition to its effects on body mass and health, the food environment in affluent societies may be creating an appetitive counterpart to the psychological effects of other hedonically-driven activities such as drug use and compulsive gambling. This phenomenon is referred to here as “hedonic hunger.” Animal literature is reviewed indicating that brain-based homeostatic and hedonic eating motives overlap but are nonetheless dissociable. In humans there is evidence that obese individuals prefer and consume high palatability foods more than those of normal weight. Among normal weight individuals it has long been assumed that the appetitive anomalies associated with restrained eating are due to diet-induced challenges to the homeostatic system, but we review evidence suggesting that they more likely stem from hedonic hunger (i.e., eating less than wanted rather than less than needed). Finally, a recently-developed measure (the Power of Food Scale; PFS) of individual differences in appetitive responsiveness to rewarding properties of the food environment is described. Preliminary evidence indicates that the PFS is reliable and valid and is related to clinically-relevant variables such as food cravings and binge eating. This measure, combined with environmental manipulations of food availability and palatability, may constitute a useful approach to studying hedonic hunger. © 2007 Elsevier Inc. All rights reserved. Keywords: Hunger; Hedonic; Reward; Appetite; Food intake; Eating; Addiction I pursue pleasure, but stingily, suspiciously. Mason Cooley The purpose of this paper is to propose and justify a distinction between homeostatic and hedonic eating and to Do not bite at the bait of pleasure, till you know there is no discuss the potential consequences of what, from an historical hook beneath it. Thomas Jefferson perspective, represents an unprecedented societal phenomenon: the constant availability and frequent consumption of highly 1. Introduction palatable foods. We agree with other observers [1] that this phenomenon is contributing to escalating obesity and its These aphorisms suggest that the attainment of pleasure is physical comorbidities (diabetes, heart disease, etc.). However, both desirable and dangerous. For the vast majority of human we also propose that the food environment may be creating an history and prehistory, the primary objective of seeking food appetitive counterpart to the psychological effects of other was survival through the maintenance of energy homeostasis hedonically-driven activities such as drug use and compulsive and the avoidance of starvation. In modern times, among well- gambling. Just as compulsive gamblers or drug-dependent nourished populations, most food consumption occurs for individuals are preoccupied with their habit even when they are reasons other than acute energy deprivation [1]. As the growing not engaging in it, so may some individuals experience frequent prevalence of global obesity suggests, an increasing proportion thoughts, feelings and urges about food in the absence of any of human food consumption appears to be driven by pleasure, short- or long-term energy deficit. These experiences may or not just by the need for calories. may not be prompted by exposure to food-related cues but by definition they do not occur in response to prolonged food deprivation (i.e., homeostatic hunger). We refer to this tendency “ ” ⁎ Corresponding author. 245 N. 15th St., MS 626, Philadelphia, PA 19102- here as hedonic hunger . 1192, USA. Tel.: +1 215 762 4948; fax: +1 215 762 7441. It is important to emphasize that the term hedonic hunger, like E-mail address: [email protected] (M.R. Lowe). the traditional concept of hunger, is meant to refer to a subjective 0031-9384/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.physbeh.2007.04.006 M.R. Lowe, M.L. Butryn / Physiology & Behavior 91 (2007) 432–439 433 state (and to physiological mechanisms that may mediate it), not state presumably reflecting an actual or impending state of to actual food intake. Research suggests that traditional self- energy deprivation. However, although the use of a period (e.g., reports of hunger are only weakly related to the amount of food at least 8 h) of food deprivation creates an unambiguous state of that is subsequently consumed [2,3], and the same may be true homeostatic hunger, it is much less clear what self-report for the concept of hedonic hunger. It also is possible that measures of subjective hunger level used in hundreds of past subjective hunger ratings are more reflective of a simple studies are actually measuring. For instance commonly-asked propensity towards eating, rather than serving as an index of questions such as “How hungry do you feel right now?”, “How how much food will be consumed. These observations do not strong is your desire to eat right now?” and “How much food do mean that measures of hedonic hunger will not predict food you think you could eat right now?” [8] were designed to assess intake, only that the term should be defined independently of what we are referring to as homeostatic hunger but, depending actual food intake. In addition, the immediate food environment on the experimental context, could just as well be tapping what is presumed to play a much greater role in the generation of we refer to as hedonic hunger. For instance, if study participants hedonic than of homeostatic hunger. The development of consumed a normal dinner and were then provided with an array homeostatic hunger is based on the prolonged absence of energy of their favorite deserts to sample ab lib, their answers to these intake. The palatability of the food that an individual is exposed questions would presumably reflect a fair degree of “hunger”, to during and between eating bouts is assumed to be largely despite having recently finished dinner. Additional evidence irrelevant to the generation of homeostatic hunger. The opposite that self-reported hunger ratings often reflect some (unknown) appears to be true of hedonic hunger. That is, satiety has a mixture of homeostatic and hedonic eating motives comes from relatively small effect on the pleasantness of foods (the a study that examined pictorial measures of physical hunger pleasantness of a meal does not decline nearly as much as (based on how many body areas were identified as reflecting hunger as the meal is consumed). Rather, the availability and current hunger levels) and traditional verbal measures of hunger palatability of foods in the immediate environment has a major repeatedly during a 22-hour fast [8]. The researchers found that effect on whether they will be desired and consumed [4-6] and an the pictorial measure increased more rapidly than the verbal individual's level of current caloric repletion is assumed to be measure as the fast proceeded and also found that correlations relatively unimportant. between the verbal and pictorial measure were few in number A further implication of these distinctions is a difference in and modest in size. These results suggest that verbal measures the experimental methods one would use to study these two of hunger used in past studies are measuring something more eating motives. Studies of homeostatic hunger would obviously than physical sensations of food deprivation. From an historical involve the manipulation of hunger via differing lengths of food perspectivetherewasnoneedtorefertohungeras deprivation. Studying hedonic hunger appears to have two “homeostatic” because this function of hunger was inherent in requirements. One is assuring that participants are in a state of the term itself. However, since both food deprivation and the short-term energy repletion — i.e., they are not in a state of availability of palatable food (when energy replete) can produce impending or actual energy deficit (e.g., shortly before a meal). strong motivations to eat, a priority for future research will be to The other is that the experimental context examining hedonic differentiate between these two types of motivation to eat. hunger involves the introduction of some kind of highly For most of the history of research on human and animal palatable food stimulus. The reason for the second requirement eating regulation it has been assumed that food intake is tightly is that the state of hedonic hunger is presumably a latent regulated by homeostatic mechanisms and that deviations in potentiality that can only be “called forth” by the introduction of energy intake in either direction will be corrected by behavioral highly-pleasurable food stimuli. and metabolic regulatory responses [9,10]. The obesity A final introductory comment is needed based on the epidemic and research on topics such as the effects of portion distinction that Berridge and Robinson have made between size and food palatability on food intake have made it “wanting” and “liking” a substance. Although these two abundantly clear that upward deflections in energy intake are motivational drives normally go hand-in-hand, these researchers not well compensated for by reductions in subsequent intake have shown that they are subserved by neurophysiological [11]. There has also been a significant increase in research and mechanisms that can be experimentally differentiated. We commentary addressing the question of how and why the previously addressed the relation of this distinction to the homeostatic system for eating regulation is being overridden distinction we are drawing between homeostatic and hedonic [7,12,13]. eating motives (see reference [7], pp. 800–801). We simply One compelling question raised by this work is whether the point out here that when discussing hedonic eating motives, concept of hunger is still relevant when discussing intake that such motives could be driven by the incentive salience of supersedes energy needs.