Eating represents a choice among many alternative behaviors. The purpose of this review is to provide an overview of how food reinforcement and behavioral choice theory are related to eating and to show how this theoretical approach may help organize research on eating from molecular genetics through treatment and prevention of obesity. Special emphasis is placed on how food reinforcement and behavioral choice theory are relevant to understanding excess energy intake and obesity and how they provide a framework for examining factors that may influence eating and are outside of those that may regulate energy homeostasis. Methods to measure food reinforcement are reviewed, along with factors that influence the reinforcing value of eating. Contributions of neuroscience and genetics to the study of food reinforcement are illustrated by using the example of dopamine. Implications of food reinforcement for obesity and positive energy balance are explored, with suggestions for novel approaches to obesity treatment based on the synthesis of behavioral and pharmacological approaches to food reinforcement. Keywords food reinforcement; food intake; choice; dopamine; behavioral genetics Choice is ubiquitous. There are many choices that people make that influence their eating and body weight, beginning with how early to get up, to exercise before breakfast or to sleep in, what to have for breakfast, and so on. These choices are made in the context of alternatives, many of which are pleasurable and exert considerable influence to do these behaviors rather than others. The morning is a good time for many people to choose to exercise, but a warm bed and a little extra sleep time represent a powerful alternative that even the most enthusiastic exerciser confronts and often succumbs to. Similarly, eating a good breakfast starts the day off right, but a pastry and coffee may be particularly inviting alternative foods that taste very good and may tempt many away from healthy cereal and fruit. This article provides a theoretical framework for understanding motivation to eat, how people make choices about eating versus engaging in other behaviors, and how these theoretical approaches can provide insights into obesity, mechanisms that regulate food choice, and implications of choice theory for interventions. One of the unique aspects of food reinforcement and behavioral theories of

The authors measured food reinforcement, polymorphisms of the dopamine D2 receptor (DRD2) and dopamine transporter (DAT1) genes, and laboratory energy intake in 29 obese and 45 nonobese humans 18-40 years old. Food reinforcement was greater in obese than in nonobese individuals, especially in obese individuals with the TaqI A1 allele. Energy intake was greater for individuals high in food reinforcement and greatest in those high in food reinforcement with the TaqI A1 allele. No effect of the DAT1 genotype was observed. These data show that individual differences in food reinforcement may be important for obesity and that the DRD2 genotype may interact with food reinforcement to influence energy intake.

Caffeine is a widely used psychoactive substance in both adults and children that is legal, easy to obtain, and socially acceptable to consume. Although once relatively restricted to use among adults, caffeine-containing drinks are now consumed regularly by children. In addition, some caffeinecontaining beverages are specifically marketed to children as young as four years of age. Unfortunately, our knowledge of the effects of caffeine use on behavior and physiology of children remains understudied and poorly understood. The purpose of this article is to review what is known about caffeine use in children and adolescents, to discuss why children and adolescents may be particularly vulnerable to the negative effects of caffeine, and to propose how caffeine consumption within this population may potentiate the rewarding properties of other substances. The following topics are reviewed: 1) tolerance and addiction to caffeine 2) sensitization and cross-sensitization to the effects of caffeine 3) caffeine self-administration and reinforcing value and 4) conditioning of preferences for caffeine-containing beverages in both adults and children.

Caffeine is the most widely consumed psychoactive drug in the world. Natural sources of caffeine include coffee, tea, and chocolate. Synthetic caffeine is also added to products to promote arousal, alertness, energy, and elevated mood. Over the past decade, the introduction of new caffeine-containing food products, as well as changes in consumption patterns of the more traditional sources of caffeine, has increased scrutiny by health authorities and regulatory bodies about the overall consumption of caffeine and its potential cumulative effects on behavior and physiology. Of particular concern is the rate of caffeine intake among populations potentially vulnerable to the negative effects of caffeine consumption: pregnant and lactating women, children and adolescents, young adults, and people with underlying heart or other health conditions, such as mental illness. Here, we review the research into the safety and safe doses of ingested caffeine in healthy and in vulnerable populations. We report that, for healthy adults, caffeine consumption is relatively safe, but that for some vulnerable populations, caffeine consumption could be harmful, including impairments in cardiovascular function, sleep, and substance use. We also identified several gaps in the literature on which we based recommendations for the future of caffeine research.

Research has shown that animals and humans habituate on a variety of behavioral and physiological responses to repeated presentations of food cues, and habituation is related to amount of food consumed and cessation of eating. The purpose of this article is to provide an overview of experimental paradigms used to study habituation, integrate a theoretical approach to habituation to food based on memory and associative conditioning models, and review research on factors that influence habituation. Individual differences in habituation as they related to obesity and eating disorders are reviewed, along with research on how individual differences in memory can influence habituation. Other associative conditioning approaches to ingestive behavior are reviewed, as well as how habituation provides novel approaches to preventing or treating obesity. Finally, new directions for habituation research are presented. Habituation provides a novel theoretical framework from which to understand factors that regulate ingestive behavior. KeywordsHabituation; food intake; ingestive behavior; Eating behavior; obesity; sensory specific satiety; energy intake Habituation as a determinant of human food intakeEating involves the repeated presentation of visual, olfactory and gustatory cues as a meal or snack is consumed. One effect of repeated stimulus presentations is habituation to those stimuli. Habituation represents a general model of how repeated stimulus presentations influence responding and is ubiquitous across response systems (Groves & Thompson, 1970). Habituation describes reductions in both physiological and behavioral responses to eating that occur as an eating episode progresses, and may provide a model to understand factors that are important for the cessation of eating, or satiation, within a meal. After the response rate to food has decreased, presentation of a new stimulus will result in recovery of responding to the new stimulus as well as recovery of responding, or dishabituation, to the habituated food stimulus (Epstein, Rodefer, Wisniewski, & Caggiula, 1992). The recovery of appetite or the motivation to eat is apparent to anyone who has consumed a large meal, and is quite full, and does not NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript require additional energy or nutrients to meet their daily needs, but decides to consume additional calories after seeing the dessert cart.It is common to consider the influence of sensory characteristics of food as being important guides to what foods to eat, and important determinants of the pleasure derived from eating (Bartoshuk, 1991;Cabanac, 1990), but habituation goes beyond this to explain factors that are important in regulating the amount of food consumed (Swithers, 1996). Habituation studies provide a framework to understand how sensory stimuli influence not only choice of food, but the amount of food consumed. One purpose of this paper is to present different experimental paradigms for studying habituation, along with consideration...

These results show that overweight children find food more reinforcing than do nonoverweight children. This individual difference was replicated in different experiments using different types of foods and food alternatives. These studies provide support for studying food reinforcement as a factor associated with overweight and obesity.

Background:Sedentary activities, such as watching television, may disrupt habituation to food cues, thereby increasing motivation to eat and energy intake. Objective: These experiments were designed to examine the effect of television watching on habituation of ingestive behavior in children. Design: In experiment 1, all children worked for access to cheeseburgers in trials 1-7 (habituating stimulus). In trials 8 -10, children in the control group continued to work for cheeseburgers without any dishabituating stimuli, whereas children in the other groups received either a novel food (French fries) or television as dishabituating stimuli. Responding for food and amount of food eaten were measured. In experiment 2, all children had access to 1000 kcal of a preferred snack food. One group watched a continuous television show, and the control groups either watched no television or watched a repeated segment of a television show, which controls for the television stimulus but requires reduced allocation of attention. Results: In experiment 1, both the novel food and the television watching groups reinstated responding for food (P ҃ 0.009) and increased the amount of energy earned (P ҃ 0.018) above the level of the control subjects. In experiment 2, the continuous television group spent more time eating (P 0.0001) and consumed more energy than the no television and the repeated segment groups (P ҃ 0.007). Conclusion: These experiments show that television watching can dishabituate eating or disrupt the development of habituation, which may provide a mechanism for increased energy intake associated with watching television.Am J Clin Nutr 2007;85:355-61.

GnRH is the master neuropeptide that coordinates and regulates reproduction in all vertebrates and in some nonvertebrate species. Sixteen forms of GnRH have been isolated in brain. In the vast majority of species, two or more forms occur in anatomically and developmental distinct neuronal populations. In mammalian brain, two GnRH forms, mammalian (GnRH-I) and chicken-II (GnRH-II), exist. The distribution and functions of GnRH-I have been well characterized and intensively studied. However, the function of GnRH-II, which is the most evolutionarily conserved form of GnRH, has been elusive. Here we demonstrate that in a primitive mammal, the musk shrew (Suncus murinus), GnRH-II activates mating behavior in nutritionally challenged females within a few minutes after administration. In addition GnRH-II immunoreactive cell numbers and fibers increase in food-restricted females. Furthermore, GnRH type II receptor immunoreactivity was detected in musk shrew brain in regions associated with mating behavior. Our results lead us to hypothesize that the role of the evolutionarily conserved GnRH-II peptide is to coordinate reproductive behavior as appropriate to the organism's energetic condition.