A behavioral economics analysis of food choice in humans

The relationship among disordered eating behavior, power of food scale and sensitization of the reinforcing value of food

INTRODUCTION

Disordered eating behaviors are a current public health concern since their progression can lead to the development of a full criteria eating disorder. Sensitization to repeated intake of high energy density (HED) foods is associated with excess weight gain over time, but less is known about relationships with assessments of disordered eating. Thus, this study aims to understand how disordered eating behaviors refunlate to the influence of the food environment and sensitization.

METHOD

163 adolescents - 50 % female and 13.2 mean age - were followed for 24 months. Sensitization was assessed by comparing the relative reinforcing value (RRV) of HED food at baseline and after two weeks of daily intake; sensitization was defined as RRV of food after repeated intake. Study participants also completed the EDE-Q, and Power of Food Scale (PFS). We conducted multivariate general linear models to examine these associations.

RESULTS

Sensitization status and PFS scores at baseline were positively associated with EDE-Q subscale scores cross-sectionally, but not longitudinally, at baseline and 24 months. We found that sensitization to HED food and higher susceptibility to food cues relates to increased disordered eating behaviors and both at baseline and at 24-months.

DISCUSSION

These findings suggest that sensitization to repeated HED food intake and the food environment might be a risk factor for later engagement in disordered eating behaviors. Future studies should address the temporal relationships among these factors and the role that social norms around body weight and weight stigma may play in the development of these behaviors.

The effectiveness of Go/No-Go and Stop-Signal training in reducing food consumption and choice: A systematic review and meta-analysis

The Go/No-Go and Stop-Signal tasks have been used to reduce excess food intake via repeated pairing of food cues with response inhibition. A meta analysis of 32 studies was conducted to determine whether, and under which conditions, the Go/No-Go and Stop-Signal training tasks are effective in reducing food consumption or choice. Moderators included task parameters (e.g., number of sessions, stop signal), sample differences (e.g., age, weight), and the measure of food consumption or choice. Overall, there was a small effect for Go/No-Go and Stop-Signal training in reducing food consumption or choice, g = -0.21, CI95 = [-0.31, -0.11], p < .001, with this holding individually only for a single session of the Go/No-Go Task, g = -0.31, CI95 = [-0.45, -0.18], p < .001. Comprehensive investigation of the impact of varying moderators indicated that the effect for Go/No-Go training was robust. Nevertheless, there was significant variation in the specific parameters of the task. Overall, the present meta-analysis extends previous findings by providing comprehensive evidence that the Go/No-Go Task is effective in reducing food consumption and choice, as well as providing optimal parameter recommendations for the task.

Changes in food preferences and ingestive behaviors after glucagon-like peptide-1 analog treatment: techniques and opportunities

BACKGROUND

Glucagon-like peptide-1 (GLP-1) analogs are approved for the treatment of obesity in adults and adolescents. Reports have emerged that the weight loss effect of these medications may be related to changes in food preferences and ingestive behaviors following the treatment. Understanding the mechanisms which impact ingestive behavior could expand opportunities to develop more refined and personalized treatment options for obesity.

METHODS

Recent studies investigating the relationship between GLP-1 analogs and ingestive behaviors were retrieved from PubMed using the search terms: "obesity," "food preference," "taste," "ingestive behavior," "weight loss medication," "anti-obesity medication," "GLP-1 analog," "tirzepatide," "liraglutide," "semaglutide." Measurement tools were studied to compare variables used to assess food intake behavior. The main outcomes from each study were analyzed to evaluate the current standing and future directions of appetitive, ingestive, and consummatory behaviors and their association with GLP-1 analogs.

RESULTS

Thus far, studies have primarily explored the weight loss phase and report decreased short-term appetite and food intake upon treatment. However, research during the weight maintenance phase and objective measurements of food intake are notably sparse. Additionally, verbal reports have been primarily used to examine food intake, which can be susceptible to subjectivity.

CONCLUSIONS

Elucidating the relationship between GLP-1 analogs and ingestive behavior could reveal additional parameters which contribute to their anti-obesity effects. To better understand these mechanisms, it is imperative to consider objective measurements of food intake in future studies. Several measurement tools have been adapted to measure variables of food behavior in humans, and each must be carefully considered with their strengths and limitations to develop optimal investigations.

Metabolic hormones mediate cognition

Recent biochemical and behavioural evidence indicates that metabolic hormones not only regulate energy intake and nutrient content, but also modulate plasticity and cognition in the central nervous system. Disruptions in metabolic hormone signalling may provide a link between metabolic syndromes like obesity and diabetes, and cognitive impairment. For example, altered metabolic homeostasis in obesity is a strong determinant of the severity of age-related cognitive decline and neurodegenerative disease. Here we review the evidence that eating behaviours and metabolic hormones-particularly ghrelin, leptin, and insulin-are key players in the delicate regulation of neural plasticity and cognition. Caloric restriction and antidiabetic therapies, both of which affect metabolic hormone levels can restore metabolic homeostasis and enhance cognitive function. Thus, metabolic hormone pathways provide a promising target for the treatment of cognitive decline.

Consumption of a Variety of Vegetables to Meet Dietary Guidelines for Americans' Recommendations Does Not Induce Sensitization of Vegetable Reinforcement Among Adults with Overweight and Obesity: A Randomized Controlled Trial

BACKGROUND

Food reinforcement, or the motivation to obtain food, can predict choice and consumption. Vegetable consumption is well below recommended amounts for adults, so understanding how to increase vegetable reinforcement could provide valuable insight into how to increase consumption.

OBJECTIVES

We sought to determine whether daily consumption of the Dietary Guidelines for Americans (DGA) recommendations for vegetable intake induces sensitization of vegetable reinforcement in adults with overweight and obesity.

METHODS

Healthy adults with a BMI ≥ 25 kg/m2 who consumed ≤1 cup-equivalent of vegetables/day were randomly assigned to a vegetable intervention (VI; n = 55) or an attention control (AC; n = 55) group. The VI consisted of the daily provision of vegetables in the amounts and types recommended by the DGA (∼270 g/day) for 8 weeks. Participants were followed for an additional 8 weeks to assess sustained consumption. Compliance was measured weekly by resonance Raman light-scattering spectroscopy (RRS). Vegetable reinforcement was tested at weeks 0, 8, 12, and 16 using a computer choice paradigm.

RESULTS

In the VI group, RRS intensity increased from week 0 to 8 (from 22,990 to 37,220), returning to baseline by week 16 (27,300). No change was observed in the AC group. There was no main effect of treatment (P = 0.974) or time (P = 0.14) and no treatment x time interaction (P = 0.44) on vegetable reinforcement. There was no moderating effect of sex (P = 0.07), age (P = 0.60), BMI (P = 0.46), delay discounting (P = 0.24), 6-n-propylthiouracil taster status (P = 0.15), or dietary disinhibition (P = 0.82) on the change in vegetable reinforcement.

CONCLUSIONS

These findings suggest no effects of the provision of a variety of vegetables to meet DGA recommendations for 8 weeks on vegetable reinforcement and highlight the difficulty in increasing vegetable consumption in adults. This trial was registered at clinicaltrials.gov as NCT02585102.

Negative energy balance during military training: The role of contextual limitations

During multiday training exercises, soldiers almost systematically face a moderate-to-large energy deficit, affecting their body mass and composition and potentially their physical and cognitive performance. Such energy deficits are explained by their inability to increase their energy intake during these highly demanding periods. With the exception of certain scenarios in which rations are voluntarily undersized to maximize the constraints, the energy content of the rations are often sufficient to maintain a neutral energy balance, suggesting that other limitations are responsible for such voluntary and/or spontaneous underconsumption. In this review, the overall aim was to present an overview of the impact of military training on energy balance, a context that stands out by its summation of specific limitations that interfere with energy intake. We first explore the impact of military training on the various components of energy balance (intake and expenditure) and body mass loss. Then, the role of the dimensioning of the rations (total energy content above or below energy expenditure) on energy deficits are addressed. Finally, the potential limitations inherent to military training (training characteristics, food characteristics, timing and context of eating, and the soldiers' attitude) are discussed to identify potential strategies to spontaneously increase energy intake and thus limit the energy deficit.

Choice is relative: Reinforcing value of food and activity in obesity treatment

Persons with obesity find high-energy-dense food and sedentary behaviors highly reinforcing. Diets and exercise programs deprive individuals of many favorite foods and activities, which can counterproductively heighten their value and lead to relapse. Since the value of reinforcers depend on the alternatives available, one approach to reducing food and sedentary activity reinforcement is to build healthy alternative reinforcers. Current behavioral treatment programs for children and adults do not attempt to build alternative reinforcers as substitutes for unhealthy behaviors to reduce the impact of food or activity deprivation on the motivation to eat or be inactive. A goal of the next generation of obesity treatment programs should focus on development of healthy behaviors as reinforcers so that people will be motivated to engage in them. This article provides an overview of relationships among reinforcers, how understanding substitutes and complements can influence eating and activity, and how enriching a person's environment and providing choice architecture can enhance weight control. Ideas for translation of these basic behavioral economic principles to obesity treatment programs are discussed. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

The relationships between eating disorder pathology and relative reinforcing value of food, delay discounting, and related constructs in adolescents

Food is a primary reinforcer that motivates behavior in the absence of learning or conditioning. Both the relative reinforcing value (RRV) of food and delay discounting are associated with weight status. While dietary restraint and disinhibition have been shown to influence the RRV of food, limited work has examined the relationships between eating disorder pathology and RRV of food and delay discounting. Therefore, the purpose of this study was to examine how eating disorder pathology predicts RRV of food, proportion of food consumed, delay discounting, reinforcement pathology (i.e., high motivation to eat and high delay discounting), and sensitization of high energy dense food (HED; i.e., increases in RRV of HED food after daily repeated exposure). Participants were 167 adolescents ages 12-14 without obesity participating in a longitudinal study examining predictors of weight change who completed a series of laboratory assessments assessing the RRV of food of HED food, delay discounting, reinforcement pathology, sensitization of HED food, and a questionnaire assessing eating disorder pathology. Eating disorder pathology was not related to the RRV of food or delay discounting, but did predict reinforcement pathology and the sensitization of HED food. When explored by weight status, these relationships were only observed for those with overweight. There were no other significant relationships for either adolescents with normal weight or overweight. Given that weight status appeared to moderate some of the relationships between eating disorder pathology and reinforcement-related constructs, future work should examine how reinforcement pathology and eating disorder pathology are related to changes in weight status over time.

Learning to lose control: A process-based account of behavioral addiction

Learning psycho(bio)logy has developed a solid corpus of evidence and theory regarding behavior control modes. The present article briefly reviews that literature and its influence on recent models in which the transition from goal-directed to compulsive behavior is identified as the main process underlying substance use disorders. This literature is also relevant to non-substance addictive disorders, and serves as basis to propose a restricted definition of behavioral addiction relying on the presence of behavior-specific compulsivity. Complementarily, we consider whether some activities can become disordered while remaining mostly goal-driven. Based on reinforcement learning models, relative outcome utility computation is proposed as an alternative mechanism through which dysfunctional behaviors (even not qualifying as addictive) can override adaptive ones, causing functional impairment. Beyond issues of conceptual delimitation, recommendations are made regarding the importance of identifying individual etiological pathways to dysregulated behavior, the necessity of accurately profiling at-risk individuals, and the potential hazards of symptom-based diagnosis. In our view, the validity of these recommendations does not depend on the position one takes in the nosological debate.

Healthy Eating: Approaching the Selection, Preparation, and Consumption of Healthy Food as Choice Behavior

Healthy eating has important well-being and financial implications for our society. As such, it is critical that the field of behavior science and behavior analysis conduct more research in this area so that effective interventions may be developed. One barrier to addressing healthy eating may be conceptual. Far from being a single response, eating is comprised of a series of choice responses. These selection, preparation and consumption responses form a temporally delayed behavioral chain. When designing interventions to address healthy eating, therefore, one must not only consider the specific target response, but alternative response options, and the effect of changing one response on other choices in the chain. The purpose of this article is to refine the analysis of healthy eating behavior, provide examples of research conducted in this area, and discuss how these interventions may influence this chain of responses. It is hoped that by doing so, additional research will be conducted and disseminated so that individuals, organizations, and policy makers can implement more effective interventions for healthy eating.

Loss Aversion of Time: Serving School Lunches Faster without Impacting Meal Experience

Loss aversion has been extensively studied in economics, but there is less discussion of it in the context of time. Results from a field experiment conducted in a U.S. public school lunch cafeteria suggest that students could be loss averse to time and that interventions, such as a pre-plated service lane could increase the speed of service and guide students to make better food choices. Faster, pre-plated service lanes may leverage loss aversion bias, be beneficial for larger schools, reduce wait time for students, and thereby increase their satisfaction with the service process.

Reinforcing value and hypothetical behavioral economic demand for food and their relation to BMI

Food is a primary reinforcer, and food reinforcement is related to obesity. The reinforcing value of food can be measured by establishing how hard someone will work to get food on progressive-ratio schedules. An alternative way to measure food reinforcement is a hypothetical purchase task which creates behavioral economic demand curves. This paper studies whether reinforcing value and hypothetical behavioral demand approaches are assessing the same or unique aspects of food reinforcement for low (LED) and high (HED) energy density foods using a combination of analytic approaches in females of varying BMI. Results showed absolute reinforcing value for LED and HED foods and relative reinforcing value were related to demand intensity (r's = 0.20-0.30, p's < 0.01), and demand elasticity (r's = 0.17-0.22, p's < 0.05). Correlations between demographic, BMI and restraint, disinhibition and hunger variables with the two measures of food reinforcement were different. Finally, the two measures provided unique contributions to predicting BMI. Potential reasons for differences between the reinforcing value and hypothetical purchase tasks were actual responding versus hypothetical purchasing, choice of reinforcers versus purchasing of individual foods in the demand task, and the differential role of effort in the two tasks. Examples of how a better understanding of food reinforcement may be useful to prevent or treat obesity are discussed, including engaging in alternative non-food reinforcers as substitutes for food, such as crafts or socializing in a non-food environment, and reducing the value of immediate food reinforcers by episodic future thinking.

The reinforcing effect of exercise in anorexia nervosa: Clinical correlates and relationship to outcome

The purpose of the current study was to examine the relative reinforcing effect of exercise compared to a non-monetary alternative reinforcer (leisure activity), and to money, before and after weight restoration in an inpatient population with anorexia nervosa (AN). Sixty-two inpatients with AN completed a progressive ratio (PR) task to earn exercise, leisure activities, or cash at low weight and after weight restoration. Measures of pathology and motivation to exercise were completed and post-treatment discharge weights were collected. Patients worked harder for exercise at low weight than after weight restoration (df = 46, t = 5.50, p < .001). PR task performance was weakly associated with a measure of commitment to exercise (low weight: r = 0.31, weight restored: r = 0.36, p < .05), but not with other clinical measures or follow-up weights. Contrary to prior suggestions, measurement of the reinforcing value of exercise among individuals with AN via a PR task does not appear valuable in assessing clinical severity or outcome. Other, simpler, self-report measures of commitment to exercise may have greater value in assessing these outcomes.

Study design for a randomized controlled trial to increase the relative reinforcing value of vegetable consumption using incentive sensitization among obese and overweight people

In this manuscript, we present the protocol for a study that applies incentive sensitization theory to improve vegetable intake in overweight and obese adults. This 8-week, randomized, controlled, community-based feeding study with an 8-week follow-up seeks to use repeated exposure to amounts of vegetables recommended by federal guidance to increase the primary outcome of the relative reinforcing value of vegetables compared to a snack food. A community-based design is used to give participants autonomy in choosing their method of exposure. Secondary outcomes include: 1) Determine potential moderators of incentive sensitization of vegetables, including genetic polymorphisms associated with food reinforcement and obesity, 6-n-propylthiouracil tasting status, and delay discounting. 2) Determine whether adding vegetables to the diet results in participants substituting low-energy-dense vegetables for energy-dense foods or whether energy-dense food consumption is independent of vegetable consumption. 3) Determine whether reductions in adiposity are associated with substitution of vegetables in the diet. 4) Determine if markers of bone turnover change. 5) Assess changes in self-reported secondary outcomes measured by questionnaire such as self-efficacy to eat vegetables. The results of this study will provide information about the drivers of individual choice to consume recommended amounts of vegetables. The understanding gained will help increase the effectiveness and sustainability of behavior-based interventions focused on improving vegetable intake. This information may also be used to assist in setting dietary guidance targets for the amounts and types of vegetables Americans can, and should, consume.

Errors as a Means of Reducing Impulsive Food Choice

Nowadays, the increasing incidence of eating disorders due to poor self-control has given rise to increased obesity and other chronic weight problems, and ultimately, to reduced life expectancy. The capacity to refrain from automatic responses is usually high in situations in which making errors is highly likely. The protocol described here aims at reducing imprudent preference in women during hypothetical intertemporal choices about appetitive food by associating it with errors. First, participants undergo an error task where two different edible stimuli are associated with two different error likelihoods (high and low). Second, they make intertemporal choices about the two edible stimuli, separately. As a result, this method decreases the discount rate for future amounts of the edible reward that cued higher error likelihood, selectively. This effect is under the influence of the self-reported hunger level. The present protocol demonstrates that errors, well known as motivationally salient events, can induce the recruitment of cognitive control, thus being ultimately useful in reducing impatient choices for edible commodities.

A qualitative evaluation of a group phone-based weight loss intervention for rural breast cancer survivors: Themes and mechanisms of success

PURPOSE

Obesity is prevalent in breast cancer survivors and is a significant risk factor for recurrence and mortality. Weight management interventions for survivors have been diverse in design (in-person vs. phone-based, group vs. individual) and yielded varying weight loss results. Given these issues, participants themselves may provide insight into treatment-based factors that contributed to their weight loss outcomes. Here, we report qualitative results from interviews with survivors in a group phone-based weight loss intervention, with the objective of identifying mechanisms that facilitated or hindered adherence and weight loss. We explored interest in paying for continued treatment as an indicator of dissemination potential.

METHODS

Individual interviews were conducted with 186 rural, obese breast cancer survivors upon completion of a 6-month weight loss intervention that produced clinically meaningful weight loss (>5 %) in 91 % of participants. A thematic analysis of the interview data was performed.

RESULTS

Five themes were identified as impacting adherence and success: (1) accountability; (2) importance of the group, with varying levels of connectedness; (3) dietary convenience; (4) difficulty maintaining intervention components that required more effort; and (5) importance of internal motivation to attributions of physical activity success or failure. Most were interested in paying to continue the program if it were extended beyond the study.

CONCLUSIONS

Key intervention components that participants attributed to their success included supportive group processes and convenience. Results highlight the group phone-based approach as a potential venue for disseminating an effective weight loss program for breast cancer survivors.

TRIAL REGISTRATION

NCT01441011.

Errors affect hypothetical intertemporal food choice in women

Growing evidence suggests that the ability to control behavior is enhanced in contexts in which errors are more frequent. Here we investigated whether pairing desirable food with errors could decrease impulsive choice during hypothetical temporal decisions about food. To this end, healthy women performed a Stop-signal task in which one food cue predicted high-error rate, and another food cue predicted low-error rate. Afterwards, we measured participants' intertemporal preferences during decisions between smaller-immediate and larger-delayed amounts of food. We expected reduced sensitivity to smaller-immediate amounts of food associated with high-error rate. Moreover, taking into account that deprivational states affect sensitivity for food, we controlled for participants' hunger. Results showed that pairing food with high-error likelihood decreased temporal discounting. This effect was modulated by hunger, indicating that, the lower the hunger level, the more participants showed reduced impulsive preference for the food previously associated with a high number of errors as compared with the other food. These findings reveal that errors, which are motivationally salient events that recruit cognitive control and drive avoidance learning against error-prone behavior, are effective in reducing impulsive choice for edible outcomes.

Role of child weight status and the relative reinforcing value of food in children's response to portion size increases

OBJECTIVE

Food portion size is an important determinant of intake in children. It remains unknown if children's weight status and relative reinforcing value of food (RRVF) interact with portion size to affect intake.

METHODS

In a randomized crossover design, 25 normal-weight and 25 obese children, ages 8-10 years, consumed dinner once a week for 3 weeks. At each dinner, the same meal was served, but the portion size of all foods (chicken nuggets, hash browns, ketchup, green beans, brownies) and a sugar-sweetened beverage (fruit punch) varied across conditions (100, 150, and 200%). Children's RRVF was assessed using a behavioral choice task.

RESULTS

There was a significant main effect of portion size condition (P = 0.003) and weight status (P = 0.0005) and a nonsignificant trend for a portion size-by-weight status interaction (P = 0.108) on intake. Mean intakes across conditions (100, 150, and 200%) were 801 ± 57, 964 ± 58, and 873 ± 57 kcal for normal-weight children and 1041 ± 57, 1129 ± 57, and 1210 ± 57 kcal for obese children, respectively. Neither the main effect of RRVF status nor the condition-by-RRVF status interaction was significant (P > 0.48).

CONCLUSIONS

Environments that offer large portions of palatable foods affect all children's intake irrespective of their weight status or how reinforcing they find food to be.

Fasting for 24 hours heightens reward from food and food-related cues

Introduction

We examined the impact of a 24 hour complete fast (vs. fed state) on two measures of food reward: 1) ‘wanting’, as measured by response to food images and by the relative-reinforcing value of food (RRV), and 2) ‘liking’, as measured by response to food images and the hedonic evaluation of foods consumed.

Methods

Utilizing a randomized crossover design, 15 subjects (9 male; 6 female) aged 28.6±4.5 yrs with body mass index 25.3±1.4 kg/m² were randomized and counterbalanced to normal feeding (FED) and 24-hour fast (FASTED) conditions. Trait characteristics were measured with the Three Factor Eating Questionnaire. Two computer tasks measured food reward: 1) RRV progressive ratio task, 2) explicit ‘liking’ and ‘wanting’ (Leeds Food Preference Questionnaire, LFPQ). Also measured were ad libitum energy intake (EI; buffet) and food ‘liking’ (visual analogue scale) of personalized stimuli.

Results

There were no significant anthropometric changes between conditions. Appetite scores, hedonic ratings of ‘liking’, and ad libitum EI all significantly increased under the FASTED condition (p<0.05). Under the FASTED condition there were significant increases in the RRV of snack foods; similarly, explicit ‘wanting’ and ‘liking’ significantly increased for all food categories. ‘Liking’ of sweet foods remained high across-meals under FASTED, but savory foods decreased in hedonic saliency.

Conclusion

Relative to a fed state, we observed an increase in hedonic ratings of food, the rewarding value of food, and food intake after a 24 hr fast. Alliesthesia to food and food cues is suggested by heightened hedonic ratings under the FASTED condition relative to FED.

Measurement of food reinforcement in preschool children. Associations with food intake, BMI, and reward sensitivity

Progressive ratio (PR) schedules of reinforcement have been used to measure the relative reinforcing value (RRV) of food in humans as young as 8 years old; however, developmentally appropriate measures are needed to measure RRV of food earlier in life. Study objectives were to demonstrate the validity of the RRV of food task adapted for use among for preschool children (3-5 y), and examine individual differences in performance. Thirty-three children completed the RRV of food task in which they worked to access graham crackers. They also completed a snack task where they had free access these foods, liking and hunger assessments, and their heights and weights were measured. Parents reported on their child's reward sensitivity. Overall, children were willing work for palatable snack foods. Boys and older children made more responses in the task, while children with higher BMI z-scores and reward sensitivity responded at a faster rate. Children who worked harder in terms of total responses and response rates consumed more calories in the snack session. This study demonstrates that with slight modifications, the RRV of food task is a valid and developmentally appropriate measure for assessing individual differences in food reinforcement among very young children.

A community-based oral health self-care intervention for Hispanic families

OBJECTIVES

A community-based intervention is described that targets oral health self-care practices among Hispanic children in the United States and is being tested in an ongoing trial. Descriptive results of baseline oral health variables are presented.

METHODS

As of January 2013, 284 Hispanic children of ages 5-7 enrolled in the Healthy Families Study in Nashville, TN, USA. Families are randomized to one of two culturally appropriate interventions.

RESULTS

At baseline, 69.6 % of children brushed at least twice daily, and 40.6 % brushed before bed daily. One-third of parents did not know if their children's toothpaste contained fluoride.

CONCLUSIONS

This intervention fills the need for community-based interventions to improve oral health self-care practices that are culturally appropriate in Hispanic families.

State dependent valuation: the effect of deprivation on risk preferences

The internal state of an organism affects its choices. Previous studies in various non-human animals have demonstrated a complex, and in some cases non-monotonic, interaction between internal state and risk preferences. Our aim was to examine the systematic effects of deprivation on human decision-making across various reward types. Using both a non-parametric approach and a classical economic analysis, we asked whether the risk attitudes of human subjects towards money, food and water rewards would change as a function of their internal metabolic state. Our findings replicate some previous work suggesting that, on average, humans become more risk tolerant in their monetary decisions, as they get hungry. However, our specific approach allowed us to make two novel observations about the complex interaction between internal state and risk preferences. First, we found that the change in risk attitude induced by food deprivation is a general phenomenon, affecting attitudes towards both monetary and consumable rewards. But much more importantly, our data indicate that rather than each subject becoming more risk tolerant as previously hypothesized based on averaging across subjects, we found that as a population of human subjects becomes food deprived the heterogeneity of their risk attitudes collapses towards a fixed point. Thus subjects who show high-risk aversion while satiated shift towards moderate risk aversion when deprived but subjects who are risk tolerant become more risk averse. These findings demonstrate a more complicated interaction between internal state and risk preferences and raise some interesting implications for both day-to-day decisions and financial market structures.

Can the reinforcing value of food be measured in bulimia nervosa?

Binge eating is a core clinical feature of bulimia nervosa (BN). Enhanced reinforcing value of food may play a role in this behavioral disturbance, but a systematic behavioral assessment of objective measures of the rewarding value of binge eating is lacking. The purpose of this study was to quantify the reinforcing value of food in BN patients as compared with normal controls. A progressive ratio (PR) computerized work task was completed under binge and non-binge instruction. The task consisted of 12 trials. The first trial required 50 keyboard taps to earn one portion of yogurt shake, and subsequent trials required progressive work increments of 200 taps for each additional portion. Completion of all 12 trials required 13,800 taps to earn 2100ml of shake. The breakpoint, defined as the largest ratio completed before a participant stopped working, was the measure of reinforcing efficacy. Ten patients and 10 controls completed the experiment. Under binge instruction, patients completed more trials and taps, and had a higher breakpoint than controls. The non-binge instruction yielded opposite findings; compared to controls, patients completed fewer trials and taps, and had a lower breakpoint. These results support the feasibility and potential utility of a PR task to quantify the reinforcing value of food in patients with BN.

Eating behavior dimensions. Associations with energy intake and body weight. A review

The purpose of this review is to spark integrative thinking in the area of eating behaviors by critically examining research on exemplary constructs in this area. The eating behaviors food responsiveness, enjoyment of eating, satiety responsiveness, eating in the absence of hunger, reinforcing value of food, eating disinhibition and impulsivity/self-control are reviewed in relation to energy intake, body mass index and weight gain over time. Each of these constructs has been developed independently, and little research has explored the extent to which they overlap or whether they differentially predict food choices, energy intake and weight gain in the naturalistic environment. Most available data show positive cross-sectional associations with body mass index, but fewer studies report associations with energy intake or food choices. Little prospective data are available to link measures of eating behaviors with weight gain. Disinhibition has the largest and most consistent body of empirical data that link it prospectively with weight gain. An overarching conceptual model to integrate the conceptual and empirical research base for the role of eating behavior dimensions in the field of obesity research would highlight potential patterns of interaction between individual differences in eating behaviors, specific aspects of the individual's food environment and individual variation in state levels of hunger and satiety.

Gastric bypass surgery for obesity decreases the reward value of a sweet-fat stimulus as assessed in a progressive ratio task

BACKGROUND

Obesity is among the leading causes of disease and death. Bariatric surgery is the most effective treatment of obesity. There is increasing evidence that after gastric bypass surgery, patients and animal models show a decreased preference for sweet and fatty foods. The underlying mechanism may include alterations in taste function.

OBJECTIVE

We hypothesize that a gastric bypass reduces the reward value of sweet and fat tastes.

DESIGN

In this prospective case-control study, 11 obese patients who were scheduled to undergo a gastric bypass and 11 normal-weight control subjects in the fed state clicked a computer mouse to receive a sweet and fatty candy on a progressive ratio schedule 10 wk apart (in patients, testing took place 2 wk before and 8 wk after gastric bypass surgery). Subjects worked progressively harder to obtain a food reward (reinforcer) until they stopped clicking (ie, the breakpoint), which was a measure of the reinforcer value. Breakpoints were assessed by the number of mouse clicks in the last completed ratio. The experiment was repeated in a different cohort by using vegetable pieces as the reinforcer.

RESULTS

Breakpoints in the test sessions of control subjects correlated highly for both reinforcers. The median breakpoint for candies, but not vegetables, was reduced by 50% in the obese group after gastric bypass. Patients with the largest reduction in the breakpoint had the largest decrease in BMI.

CONCLUSIONS

Gastric bypass surgery resulted in the selective reduction of the reward value of a sweet and fat tastant. This application of the progressive ratio task provided an objective and reliable evaluation of taste-driven motivated behavior for food stimuli after obesity surgery.

Usual energy intake mediates the relationship between food reinforcement and BMI

The relative reinforcing value of food (RRV(food)) is positively associated with energy consumed and overweight status. One hypothesis relating these variables is that food reinforcement is related to BMI through usual energy intake. Using a sample of two hundred fifty-two adults of varying weight and BMI levels, results showed that usual energy intake mediated the relationship between RRV(food) and BMI (estimated indirect effect = 0.0027, bootstrapped 95% confidence intervals (CIs) 0.0002-0.0068, effect ratio = 0.34), controlling for age, sex, minority status, education, and reinforcing value of reading (RRV(reading)). Laboratory and usual energy intake were correlated (r = 0.24, P < 0.001), indicating that laboratory energy intake could provide an index of eating behavior in the natural environment. The mediational relationship observed suggests that increasing or decreasing food reinforcement could influence body weight by altering food consumption. Research is needed to develop methods of modifying RRV(food) to determine experimentally whether manipulating food reinforcement would result in changes in body weight.

Relative Reinforcing Value of Energy-dense Snack Foods: In Overweight and Obese Adults

Purpose: Obese people find energy-dense food more reinforcing than do their non-obese peers, and reinforcement influences food intake. We examined how the degree of adiposity, measured by body mass index (BMI), is associated with the relative reinforcing value of energy-dense snack foods versus fruits and vegetables in overweight and obese people.

Methods: Ninety-two overweight or obese students in introductory psychology courses completed questionnaires on age, sex, BMI, hunger, smoking status, dietary restraint, and hedonic (liking) ratings for energy-dense snack foods and fruits and vegetables. The questionnaire also was used to evaluate the relative reinforcing value of these snack foods in comparison with fruits and vegetables.

Results: The BMI predicted the relative reinforcing value of energy-dense snack food. This positive relationship remained significant after we controlled for age, sex, dietary restraint, hunger, smoking status, and snack food hedonics.

Conclusions: The greater the degree of overweight and obesity, the greater the motivation to obtain energy-dense snack foods. Because the rewarding value of food is a strong determinant of energy intake, a useful approach to preventing and treating obesity may be introducing pharmacological or behavioural nutrition intervention to reduce the rewarding value of energydense snack foods, or increasing the rewarding value of fruits and vegetables.

Food reinforcement and obesity. Psychological moderators

The relative reinforcing value of food (RRV(food)) provides an index of the motivation to eat. Research has shown that RRV(food) is higher in obese individuals than their non-obese peers, is associated with greater energy intake, predicts weight gain and interacts with impulsivity to predict energy intake. This study was designed to determine whether dietary restraint, dietary disinhibition or hunger moderate the effect of RRV(food) on the weight status and energy intake in 273 adults of various body mass index (BMI) levels. Hierarchical regression was used to assess the independent effects of RRV(food) on BMI and energy intake, controlling for age, sex, income, education, minority status, and RRV(reading). Results showed that greater RRV(food), but not RRV(reading), was associated with greater BMI and energy intake. Dietary disinhibition and dietary restraint moderated the relationship between RRV(food) and BMI, with dietary disinhibition being a stronger moderator of this relationship (r(2)=0.20) than dietary restraint (r(2)=0.095). In addition, dietary disinhibition moderated the effect of RRV(food) on energy intake. These results replicate the importance of RRV(food) as a predictor of obesity, and show that psychological factors moderate the effect of food reinforcement on body weight and energy intake. This trial was registered at clinicaltrials.gov as NCT00962117.

Food reinforcement, energy intake, and macronutrient choice

BACKGROUND

Food is a powerful reinforcer that motivates people to eat. The relative reinforcing value of food (RRV(food)) is associated with obesity and energy intake and interacts with impulsivity to predict energy intake.

OBJECTIVE

How RRV(food) is related to macronutrient choice in ad libitum eating tasks in humans has not been studied; however, animal research suggests that sugar or simple carbohydrates may be a determinant of reward value in food. This study assessed which macronutrients are associated with food reinforcement.

DESIGN

Two hundred seventy-three adults with various body mass indexes were assessed for RRV(food), the relative reinforcing value of reading, food hedonics, energy intake in an ad libitum taste test, and usual energy intake derived from repeated 24-h dietary recalls. Multiple regression was used to assess the relation between predictors of total energy and energy associated with macronutrient intake after control for age, sex, income, education, minority status, and other macronutrient intakes.

RESULTS

The results showed that the relative proportion of responding for food compared with reading (RRV(prop)) was positively related to body mass index, laboratory-measured energy intake, and usual energy intake. In addition, RRV(prop) was a predictor of sugar intake but not of total carbohydrate, fat, or protein intake.

CONCLUSION

These results are consistent with basic animal research showing that sugar is related to food reward and with the hypothesis that food reward processes are more strongly related to eating than are food hedonics. This trial was registered at clinicaltrials.gov as NCT00962117.

Self-control and impulsiveness in children and adults: Effects of food preferences

Experiment 1 used 6 preschool boys and Experiment 2 used 6 adult women to explore the effects of food preference on humans' choice in self-control paradigms. The boys showed a higher proportion of responses for more delayed, larger reinforcers (a measure of self-control) when those choices resulted in receipt of the most preferred food compared to when those choices resulted in the least preferred food. Further, the boys chose the less delayed, smaller reinforcers significantly more often when only those choices, as opposed to both choices, resulted in the most preferred food. Conversely, they chose the more delayed, larger reinforcers significantly more often when only those choices, as opposed to both choices, resulted in the most preferred food. Finally, the women demonstrated significantly less sensitivity to reinforcer amount relative to sensitivity to reinforcer delay (another measure of self-control) when they had a higher preference for the juice received as the less delayed, smaller reinforcer than for the juice received as the more delayed, larger reinforcer. Together, the results show that subjects' food preferences can influence self-control for food reinforcers.

Will work for snack food: the association of BMI and snack reinforcement

It has been suggested that for overweight and obese individuals high-calorie foods are more reinforcing than for normal-weight individuals. It has already been shown that in contrast to sedentary activities, snack food is more reinforcing for obese women, relative to normal-weight women. However, it is unclear whether overweight/obese individuals are more sensitive to the reinforcing value of food in general or more specifically to the reinforcing value of high-calorie foods. This was tested in the present study, with overweight/obese and normal-weight individuals performing a concurrent schedules task, which measures how hard someone is prepared to work for high-calorie snacks compared to low-calorie foods (e.g., fruits, vegetables), when both foods are equally liked. By gradually increasing the amount of work required to earn snacks, the relative-reinforcing value of snacks was determined. As hypothesized, overweight/obese individuals work harder for high-calorie snacks compared to normal-weight individuals.

The relative reinforcing value of food predicts weight gain in a longitudinal study of 7--10-y-old children

BACKGROUND

The relative reinforcing value (RRV) of food, defined as how hard an individual is prepared to work to gain access to food rather than a nonfood alternative, has been shown to be higher in obese adults and children than in their normal-weight counterparts. However, these cross-sectional studies are unable to determine whether a high RRV of food is predictive of adiposity change or whether it is a consequence of being obese.

OBJECTIVE

The objective was to examine the association between the RRV of food and 1-y weight gain in children aged 7-10 y.

DESIGN

An observational longitudinal study design was used. The RRV of food was determined by using a questionnaire method at baseline when the children (n = 316) were aged 7-9 y. Adiposity [body mass index (BMI), BMI SD score, fat mass index, waist circumference, and waist circumference SD score] was assessed at baseline and after 1 y.

RESULTS

Regression analyses indicated that the RRV of food was not associated with any measure of adiposity at baseline or at the 1-y follow-up (all P > 0.58). Changes in BMI (B = 0.06, P < 0.001), BMI SD score (B = 0.03, P = 0.001), and fat mass index (B = 0.09, P = 0.001) after 1 y were significantly predicted by the RRV of food at baseline.

CONCLUSIONS

The RRV of food predicted the change in adiposity over a relatively short-term period of 1 y and thus may be associated with the development of obesity. The lack of association in cross-sectional analyses indicates that this behavior is a risk factor for weight gain, although weight differences may not emerge until later childhood.

Effects of dietary restraint and body mass index on the relative reinforcing value of snack food

The present study examined the independent and interactive association between dietary restraint, body mass index (BMI) and the relative reinforcing value of food. Four hundred and three introductory psychology students completed questionnaires assessing age, gender, BMI, hunger, smoking status, nicotine dependence, dietary restraint, hedonic ratings for snack food and fruits and vegetables and the relative reinforcing value of snack food and fruits and vegetables. In the overall sample, results indicated a dietary restraint x BMI interaction after controlling for age, hunger, nicotine dependence, and hedonics. However, when regression models were separated by gender, the BMI x restraint interaction emerged only for females and not for males. Findings suggest that BMI moderates the relationship between dietary restraint and snack food reinforcement in females only, such that restraint and snack food reinforcement are inversely correlated in females with lower BMI, but restraint is positively correlated with snack food reinforcement in females with higher BMI. Theoretical and clinical implications of these findings are discussed.

Effects of temptation and weight on hedonics and motivation to eat in women

OBJECTIVE

The aim of the present study was to examine the extent to which food temptation influences liking, the hedonics of food, and wanting, the motivation to eat, and whether this effect differed between normal-weight and overweight women.

METHODS AND PROCEDURES

Ninety-seven normal-weight and overweight women participated in a randomized experiment, which used a two-by-two design with food temptation and body weight as independent variables. ANOVAs tested the effect of these factors on wanting and liking.

RESULTS

The most important finding of this study was that food temptation had a significant effect on wanting, but not on liking. Wanting was mainly influenced by temptation; however, this effect was moderated by weight. Interestingly, temptation caused a decrease in wanting, but only in normal-weight women. This effect of temptation could not be explained by a change in affect after manipulation or a difference in hunger before the start of the experiment.

DISCUSSION

A possible explanation for the finding that normal-weight women showed a decline in wanting after the confrontation with highly palatable food may be that normal-weight women are protected by a higher sensory-specific satiety. Moreover, it is possible that in these women goals regarding, for example, weight maintenance are more easily evoked, which may remind them of the positive consequences of not yielding into temptation.

Use of an operant task to estimate food reinforcement in adult humans with and without BED

OBJECTIVE

The purpose of this study was to demonstrate the utility of food-reinforced operant task performance in modeling binge-eating disorder (BED). We hypothesized that food reinforcement after a caloric preload would be related to BED status, but not hunger.

METHODS AND PROCEDURES

We investigated the association between reports of hunger, binge tendency, and food reinforcement in a sample of 18 women (12 non-BED, 7 lean, 5 obese, and 6 obese BED). Participants completed two sessions of operant task performance after consuming 600 ml of flavored water or 600 ml of a 1 kcal/ml liquid meal.

RESULTS

Under the water condition, food reinforcement did not differ between the non-BED and BED groups, and was positively correlated with hunger ratings across all participants (r = 0.55, P = 0.023). Under the liquid meal condition, food reinforcement was significantly decreased compared with the water condition in the non-BED group (t = -2.6, P = 0.026). There was also a significant difference between the non-BED and BED groups in the fed condition (41 +/- 40, 117 +/- 60, F = 10.3, P = 0.005, non-BED vs. BED, respectively, mean +/- s.d.). The correlation between food reinforcement and hunger remained significant only in the non-BED group (r = 0.69, P = 0.011).

DISCUSSION

Our results support the hypothesis that food reinforcement measured after a caloric preload is related to BED status but not hunger in those subjects with BED. The data also suggest that operant task performance can be useful in modeling BED criteria such as "eating when not physically hungry."

Overweight children find food more reinforcing and consume more energy than do nonoverweight children

BACKGROUND

The reinforcing value of food is a reliable index of motivation to eat and energy intake. Obese adults find food more reinforcing than do nonobese adults.

OBJECTIVE

The present study was designed to assess whether the relative reinforcing value of food differs as a function of weight status in 8-12-y-old children and whether the relative reinforcing value of food differs depending on the types of available nonfood alternatives.

DESIGN

The reinforcing value of pizza (experiment 1) or snack foods (experiment 2) was measured on progressive ratio schedules of reinforcement in nonoverweight and overweight children. Experiment 2 also compared the relative reinforcing value of food and 2 nonfood alternatives: time to spend playing a hand-held video game or time to spend reading magazines or completing word searches or mazes.

RESULTS

In both experiments, overweight children found food more reinforcing and consumed more energy than did their leaner peers. In experiment 2, the relative reinforcing value of food versus sedentary activity was higher in overweight children, but lower in nonoverweight children, regardless of the type of alternative activity available.

CONCLUSIONS

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.

Food reinforcement and eating: a multilevel analysis

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.