Food reinforcement

The Psychological Impact of the Widespread Availability of Palatable Foods Predicts Uncontrolled and Emotional Eating in Adults

This study aimed to investigate the role of the psychological impact of environments rich in palatable foods on three aspects of eating behavior: cognitive restraint (CR), uncontrolled eating (UE), and emotional eating (EE). The hypotheses were as follows: (a) The psychological impact (i.e., motivation to eat) of an environment rich in palatable foods will positively predict CR, UE, and EE; (b) dieting will predict CR, UE, and EE; and (c) CR, UE, and EE will positively predict body mass index (BMI). This study had a cross-sectional design in which data were collected online from 413 subjects. The psychological impact of food-rich environments (food available, food present, and food tasted) was assessed using the Power of Food Scale (PFS), and CR, UE, and EE were assessed using the Three-Factor Eating Questionnaire (TFEQ-R18). Both instruments were tested for confirmatory factor analysis. The relationship between constructs was measured using partial least-square structural equation modeling (PLS-SEM). "Food available" positively predicted all TFEQ-R18 factors (p < 0.01). "Food present" positively predicted UE (p < 0.001) and EE (p = 0.01). People currently on a diet showed higher levels of CR (p < 0.001) and EE (p = 0.02). UE and EE positively predicted BMI. Thus, CR, UE, and EE were positively predicted by the motivation to consume palatable foods in varying proximity, suggesting that the presence of food and, more importantly, its general availability may be important determinants of eating behavior, particularly UE and EE. Health strategies should consider the influence of the food environment to prevent and better manage impairments in eating behavior. Sex differences suggest that special attention should be paid to women. Furthermore, dieting was associated with higher levels of EE, which in turn was associated with higher BMI. Weight loss interventions should consider this vulnerability.

The Influence of Relative Reinforcing Value of Food, Sensitization, Energy Intake and Diet Quality on zBMI Change over Two Years in Adolescents: A Longitudinal Cohort Study

The relative reinforcing value (RRV) of food and sensitization are associated with zBMI and zBMI change over time, but the mechanisms underlying these relationships is unknown. The purpose of this study was to test the hypothesis that greater RRV and sensitization to HED food is associated with lower diet quality and greater energy intake at baseline and again at 24 months and that these relationships result in greater zBMI gain. The RRV of HED and LED food and dietary intake were measured at baseline and again after 24 months in a cohort of 202 boys and girls of 12-14 years old. The baseline RRV of HED food was associated with lower diet quality and lower energy intake at 24 months. zBMI gain was positively associated with the baseline energy intake but not baseline RRV of HED food or diet quality. However, diet quality moderated the relationship between baseline energy intake and zBMI change, with no difference in zBMI change as a function of energy intake when diet quality was high but significant and opposite relationships with energy intake when diet quality was low. This study suggests that high diet quality can reduce the negative impact of greater energy intake on zBMI change in adolescents.

The Effect of Financial Scarcity on Reinforcer Pathology: A Dyadic Developmental Examination

This study investigated the effects of experimentally manipulated scarcity on the reinforcing value of food (RRVfood) and delay discounting (DD), which, together, create reinforcer pathology (RP) among parents and offspring. A stratified sample of 106 families (53 parent/child aged 7−10 dyads & 53 parent/adolescent aged 15−17 dyads) from high- and low-income households visited our laboratory for three appointments. Each appointment included an experimental manipulation of financial gains and losses and DD and RRV tasks. The results showed that, regardless of food insecurity or condition, children had greater RP (β = 1.63, p < 0.001) than adolescents and parents. DD was largely unaffected by acute scarcity in any group, but families with food insecurity had greater DD (β = −0.09, p = 0.002) than food-secure families. Food-insecure parents with children responded to financial losses with an increase in their RRVfood (β = −0.03, p = 0.011), while food-secure parents and food-insecure parents of adolescents did not significantly change their responding based on conditions. This study replicates findings that financial losses increase the RRVfood among adults with food insecurity and extends this literature by suggesting that this is strongest for parents of children.

Prospective relations of maternal reward-related eating, pregnancy ultra-processed food intake and weight indicators, and feeding mode with infant appetitive traits

Background

Infant appetitive traits including eating rate, satiety responsiveness, food responsiveness, and enjoyment of food predict weight gain in infancy and early childhood. Although studies show a strong genetic influence on infant appetitive traits, the association of parent and infant appetite is understudied. Furthermore, little research examines the influence of maternal pregnancy dietary intake, weight indicators, and feeding mode on infant appetite. The present study investigated relations of maternal reward-related eating, pregnancy ultra-processed food intake and weight indicators, and feeding mode with infant appetitive traits.

Methods

Mothers in the Pregnancy Eating Attributes Study (458 mothers enrolled, 367 retained through delivery) completed self-report measures of reward-related eating, and principal component analysis yielded two components: (1) food preoccupation and responsiveness and (2) reinforcing value of food. Mothers completed 24-h dietary recalls across pregnancy, and the standardized NOVA (not an acronym) system categorized recalled foods based on processing level. Maternal anthropometrics were measured across pregnancy. At infant age 6 months, mothers reported on feeding mode and infant appetitive traits. Linear regressions were conducted predicting infant appetitive traits from household income-poverty ratio (step 1); maternal reward-related eating components (step 2); pregnancy ultra-processed food intake (% of energy intake), early pregnancy body mass index, and gestational weight gain (step 3); and exclusive breastfeeding duration (step 4).

Results

A 1-SD greater maternal food preoccupation and responsiveness was associated with 0.20-SD greater infant satiety responsiveness (p = .005). A 1-SD greater % energy intake from ultra-processed foods during pregnancy was associated with 0.16-SD lower infant satiety responsiveness (p = .031). A 1-SD longer exclusive breastfeeding duration was associated with 0.18-SD less infant food responsiveness (p = .014). Other associations of maternal reward-related eating, pregnancy ultra-processed food intake and weight indicators, and feeding mode with infant appetitive traits were non-significant.

Conclusions

Proximal early-life environmental factors including maternal pregnancy dietary intake and feeding mode may facilitate or protect against obesogenic infant appetitive traits, whereas infant appetite may not parallel maternal reward-related eating. Further investigation into the etiology of appetitive traits early in development, particularly during solid food introduction, may elucidate additional modifiable risk factors for child obesity.

Trial registration

Clinicaltrials.gov. Registration ID – NCT02217462. Date of registration – August 13, 2014.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12966-022-01334-9.

The effect of acute and chronic scarcity on acute stress: A dyadic developmental examination

BACKGROUND

Food insecurity, obesity, and psychological stress are interrelated constructs which are thought to be connected through increased energy intake, but the underlying mechanisms for these relationships remain unclear. The current study used experimental methods to investigate how financial losses may influence acute stress in the context of food insecurity for both parents and offspring. This study also sought to examine the effect of acute stress related to financial losses on the reinforcing value of food (RRV_food) and delay discounting (DD).

METHODS

One hundred and six families stratified by both offspring age (53 children aged 7-10, 53 adolescents aged 15-17) and household financial resources, visited our laboratory for three separate appointments. Each appointment included the experimental manipulation of financial gains and losses, saliva samples for cortisol assay, continuous heart rate monitoring, self-rated tension, and computer-based DD and RRV_food tasks. Participants also completed surveys to report perceived life stress level and food insecurity status.

RESULTS

Among all participants, financial losses were related to decreased heart rates and increased self-rated tension. Among parents reporting food insecurity, acute financial losses resulted in an increase in cortisol levels. Changes in cortisol, heart rate, and tension were not related to RRV_food or DD.

CONCLUSION

Food insecure parents are sensitive to financial losses and respond with an increase in cortisol. However, we found no evidence for a relationship between cortisol and RRV_food or DD. This sensitivity to financial losses did not extend to children or adolescents.

The effect of personal relative deprivation on food choice: An experimental approach

Growing evidence suggests that relative disadvantage is more relevant than absolute socioeconomic factors in explaining disparities in healthfulness of diet. In a series of pre-registered experiments, we tested whether personal relative deprivation (PRD), i.e. the sense that one is unfairly deprived of a deserved outcome relative to others, results in choosing more palatable, rewarding foods. Study 1 (N = 102) demonstrated the feasibility and effectiveness of a game for inducing real-time experiences of PRD. Study 2 (N = 287) showed no main effect of PRD condition on hypothetical food choices, but an interaction between chronic PRD and condition revealed that those in the PRD condition chose more rewarding foods when feeling chronically deprived. In Study 3 (N = 260) the hypothesized main effect was found on real, non-hypothetical food choices: those in the PRD condition chose more rewarding foods, controlling for sensitivity to palatable food. Our results provide preliminary indications that the experience of being relatively deprived, rather than the objective amount or resources, may result in a higher preference for high-caloric and palatable foods. It may be suggested that efforts to reduce societal disparities in healthfulness of diet may need to focus on perceptions of injustice beyond objective inequalities.

Influence of fat-free mass and resting metabolic rate on increased food reinforcement after exercise training

Purpose

Models of appetite control have been largely based on negative feedback from gut and adipose signaling to central appetite centers. However, contemporary models posit that fat-free mass (FFM) or the energy demand of FFM [i.e., resting metabolic rate (RMR)] may play a primary role in the motivational drive for food intake (i.e., food reinforcement). The relative reinforcing value of food (RRVfood) is associated with energy intake (EI) and increases with an acute energy deficit. Chronic exercise-induced energy deficits lead to alterations in fat mass (FM), FFM, and RMR and provide an opportunity to test whether change in (∆) FM, ∆FFM, ∆usual EI, or ∆RMR are associated with ∆RRVfood.

Methods

Participants (n = 29, BMI = 25–35 kg/m2) engaged in aerobic exercise expending 300 or 600 kcal, 5 days/weeks for 12 weeks. The reinforcing value of food (PMaxfood) was measured via a computer-based operant responding task and RRVfood was calculated as the reinforcing value of food relative to non-eating sedentary behaviors. RMR was determined by indirect calorimetry and body composition by DXA.

Results

Post-training FFM correlated with usual post-training EI (rs = 0.41, p < 0.05), PMaxfood (rs=0.52, p < 0.01), and RMR (rs = 0.85, p < 0.0001). ∆RMR negatively correlated with ∆PMaxfood (rs = − 0.38, p < 0.05) and with ∆RRVfood (rs = − 0.37, p < 0.05). ∆PMaxfood and ∆RRVfood were not associated with ∆FFM (p = 0.71, p = 0.57, respectively).

Conclusions

Reductions in RMR with weight loss may increase food reinforcement as means of restoring FFM and RMR to pre-weight loss amounts. Limiting reductions in RMR during weight loss may benefit weight maintenance by restricting increases in food reinforcement after weight loss.

Interactions among Reward Sensitivity and Fast-Food Access on Healthy Eating Index Scores in Adolescents: A Cross-Sectional Study

Food cues in the environment may contribute to obesity as the consumption of unhealthy foods may reinforce reward pathways in the brain. To understand how person-level differences in reward sensitivity may be associated with diet quality, this study aimed to examine the moderating role of the availability of fast food in the environment on the relationship between reward sensitivity and diet quality in adolescents. Participants (n = 152; 55% female; Mage: 12.5 ± 0.93 y) completed the drive and reward subscales of the Behavioral Inhibition System (BIS)/Behavioral Activation System (BAS) Scale to assess reward sensitivity and completed two 24 h dietary recalls from which Healthy Eating Index (HEI) scores (total score and subscales of adequacy and moderation) were calculated. Fast-food environment (FFE) was operationalized as the total number of fast-food outlets within 1 km around participants' home address. Linear regressions were used to examine the main effects and interactions between reward sensitivity and FFE in relation to HEI score. Interactions were found between FFE and BAS drive (p = 0.02) and BAS reward (p < 0.01) on HEI adequacy. There were no interaction effects on HEI moderation or HEI total scores. For individuals who had lower access exposure to fast-food outlets (-1 SD), there was a stronger positive association between higher BAS drive (t = 2.85, p = 0.01, 95% CI (0.35, 1.94)) and HEI adequacy scores and between higher BAS reward (t = 3.27, p > 0.01, 95% CI (0.72, 2.93)) and HEI adequacy scores. By examining reward sensitivity to potential food cues in residential neighborhood food environments, it is possible to understand which adolescents are more sensitive to environmental food cues and implement interventions to buffer these influences.

The Satiation Framework: Exploring processes that contribute to satiation

Satiation has been described as a process that leads to the termination of eating and controls meal size. However, studies have shown that the termination of eating can be influenced by multiple behavioral and biological processes over the course of a meal as well as those related to the context in which the meal is consumed. To expand understanding of how individuals experience satiation during a meal, we recently developed the Reasons Individuals Stop Eating Questionnaire (RISE-Q). The development of the RISE-Q revealed five distinct factors reported to contribute to meal termination: Planned Amount, Self-Consciousness, Decreased Food Appeal, Physical Satisfaction, and Decreased Priority of Eating. Thus, we define satiation as a series of dynamic processes that emerge over the course of a meal to promote meal termination. We suggest that each of the factors identified by the RISE-Q represents a distinct process, and illustrate the contribution of each process to meal termination in the Satiation Framework. Within this framework the prominence of each process as a reason to stop eating likely depends on meal context in addition to individual variability. Therefore, we discuss contexts in which different processes may be salient as determinants of meal termination. Expanding the definition of satiation to include several dynamic processes as illustrated in the Satiation Framework will help to stimulate investigation and understanding of the complex nature of meal termination.

Expectancy to Eat Modulates Cognitive Control and Attention Toward Irrelevant Food and Non-food Images in Healthy Starving Individuals. A Behavioral Study

It is thought that just as hunger itself, the expectancy to eat impacts attention and cognitive control toward food stimuli, but this theory has not been extensively explored at a behavioral level. In order to study the effect of expectancy to eat on attentional and cognitive control mechanisms, 63 healthy fasting participants were presented with an affective priming spatial compatibility Simon task that included both food and object (non-food) distracters. The participants (N = 63) were randomly assigned to two groups: an "immediate expectancy" group made up of participants who expected to eat immediately after the task (N = 31; females = 21; age = 26.8 ± 9.6) and a "delayed expectancy" cohort made up of individuals who expected to eat a few hours later (N = 32; females = 21; age = 25.0 ± 8.0). Slower reaction times (RTs) toward the food and non-food distracters and a more pronounced effect on the RTs in the incompatible condition [i.e., the Simon effect (SE)] were noted in both groups. The effect of the food and non-food distracters on the RTs was more pronounced in the immediate with respect to the delayed expectancy group. The magnitude of the SE for the food and the non-food distracters was also greater in the immediate with respect to the delayed expectancy group. These results seem to indicate that when the expectancy to eat is short, the RTs are delayed, and the SE is more pronounced when food and non-food distracters are presented. Instead, when the expectancy to eat is more distant, the distracters have less of an effect on the RTs and the correspondence effect is smaller. Our results suggest that the expectancy to eat can modulate both attention orienting and cognitive control mechanisms in healthy fasting individuals when distracting details are competing with information processing during goal directed behavior.

Varenicline rescues nicotine-induced decrease in motivation for sucrose reinforcement

Varenicline is one of the top medications used for smoking cessation and is often prescribed before termination of nicotine use. The effect of this combined nicotine and varenicline use on the reward system and motivation for primary reinforcement is underexplored. The goal of this study was to assess the effects of nicotine and varenicline on motivation for a food reinforcer. In Experiment 1, we first assessed the responding for sucrose after pretreatment with nicotine (0, 0.1, or 0.4 mg/kg) and varenicline (0.0, 0.1, 1.0 mg/kg) using a behavioral economics approach. The responding for sucrose was then assessed using a progressive ratio schedule of reinforcement after pretreatment with all possible combinations of nicotine and varenicline doses. In Experiment 2, rats were assessed for the consumption of sucrose in home cages after pretreatment with nicotine and varenicline. We found that (a) nicotine decreased economic demand for sucrose, (b) varenicline rescued nicotine-induced reduction in economic demand for sucrose, and (c) history of varenicline treatment predicted responding for sucrose on a progressive ratio schedule of reinforcement where rats with a history of varenicline treatment responded significantly lower for sucrose across nicotine doses than rats that had not been exposed to varenicline. The results of Experiment 2 largely confirmed that nicotine decreases motivation for sucrose using a passive consumption protocol and that varenicline rescues this effect. Overall, these findings suggest that varenicline interacts with the effects of nicotine by restoring nicotine-induced reduction in motivation for appetitive rewards.

Salt need needs investigation

Expensive and extensive studies on the epidemiology of excessive Na intake and its pathology have been conducted over four decades. The resultant consensus that dietary Na is toxic, as well as the contention that it is less so, ignores the root cause of the attractiveness of salted food. The extant hypotheses are that most Na is infiltrated into our bodies via heavily salted industrialised food without our knowledge and that mere exposure early in life determines lifelong intake. However, these hypotheses are poorly evidenced and are meagre explanations for the comparable salt intake of people worldwide despite their markedly different diets. The love of salt begins at birth for some, vacillates in infancy, climaxes during adolescent growth, settles into separate patterns for men and women in adulthood and, with age, fades for some and persists for others. Salt adds flavour to food. It sustains and protects humans in exertion, may modulate their mood and contributes to their ailments. It may have as yet unknown benefits that may promote its delectability, and it generates controversy. An understanding of the predilection for salt should allow a more evidence-based and effective reduction of the health risks associated with Na surfeit and deficiency. The purpose of this brief review is to show the need for research into the determinants of salt intake by summarising the little we know.

Development of a measure of the relative reinforcing value of food versus parent-child interaction for young children

The relative reinforcing value (RRV) of food captures individual differences in the motivation to eat and is associated with weight status among infants, children, and adults. Currently, there is no concurrent measure of the RRV of food versus a non-food alternative for 4-to-5-year-old children. The present study aimed to develop and validate a measure of the RRV of food versus time spent interacting with a parent in the context of reading among 4-to-5-year-old children. The first phase of the study involved an online survey. Parents of 4-to-5 year olds (n = 102) reported their children's consumption frequency and liking for thirty-six snack foods. A priori criteria were used to identify snacks that were well-liked and served at least sometimes for use in the subsequent laboratory study. Then, a validation study was conducted in the laboratory to examine the construct validity of the finalized RRV task. Thirty-one parent-child dyads completed a laboratory visit, in which children's RRV of food versus time spent reading with a parent was measured concurrently on a progressive ratio reward schedule. Linear regression was used to assess validity of the task. Children's RRV of food positively and significantly predicted BMI z-scores among children with complete data (B = 0.41, p < 0.05, n = 28). Maximum schedules reached for food also positively and significantly predicted BMI z-scores (B = 0.30, p < 0.05). The relationship between maximum schedules reached for parent-child reading and BMI z-scores was in the expected direction, but this relationship was non-significant. Results support the validity and feasibility of the RRV paradigm used in the present study. Future research could continue to examine the measurement properties of this paradigm, as well as the potential for positive parent-child interactions to serve as a novel alternative to food.

The association of food insecurity with the relative reinforcing value of food, BMI, and gestational weight gain among pregnant women

OBJECTIVE

Food insecurity is associated with obesity among adults. During pregnancy, food insecurity increases obesity risk among mothers and infants. This study investigated the association of food security with pre-pregnancy body mass index (BMI), gestational weight gain (GWG) adequacy to date, and the relative reinforcing value (RRV) of food during pregnancy.

METHODS

This secondary data analysis examined 258 pregnant women (mean gestational age = 21.21 ± 10.21 weeks) surveyed on pre-pregnancy weight, height, pregnancy due date and GWG to date, current diagnoses related to eating and pregnancy, and demographics. The survey also assessed current food security and RRV of meals, snacks, cognitive activities, and active activities. BMI was calculated from pre-pregnancy height and weight (kg/m²). Gestational weight gain adequacy to date was derived from the Institute of Medicine guidelines. Multivariable linear regression models were used to examine the relation of food security with pre-pregnancy BMI and RRVs of foods/activities. The relation between food security and GWG adequacy to date was examined using multinomial regression models.

RESULTS

Lower food security was related to both greater pre-pregnancy BMI (β = 0.60, p < .001) and greater RRV of snack foods (β = 3.46, p < .05), after controlling for covariates. Lower food security was also related to GWG to date below recommended levels (OR = 1.25, p < .05).

CONCLUSIONS

Food insecurity is related to higher relative food reinforcement during pregnancy, and greater pre-pregnancy weight status. Future research should replicate and extend these findings by assessing them longitudinally to better evaluate the directions of these relationships.

Early Nonfood Parent-Infant Interactions and Development of Obesity in a High-Risk, Diverse Sample

OBJECTIVE

This study aimed to understand the protective role of positive mother-infant interactions in the context of food and nonfood behaviors against obesity risk later in life among a cohort of low-income children at high prenatal risk due to maternal substance use during pregnancy.

METHODS

The sample consisted of 216 mother-infant dyads (49% boys) participating in an ongoing longitudinal study. Mother-infant interactions during a feeding episode and a free-play task were measured at child age 1 and 7 months, respectively. Children's length/height and weight were measured at 1, 7, 13, 24, 36, and 48 months of age; at kindergarten age (approximately 60 months); and in second grade (approximately 84 months). BMI growth trajectories were modeled.

RESULTS

No significant associations were found between mother-child feeding interactions and child BMI trajectories. Maternal warmth (95% CI: -0.020 to -0.0005; P = 0.04) and child positive affect (95% CI: -0.020 to -0.002; P = 0.014) during free play were associated with a more normative child BMI trajectory.

CONCLUSIONS

Results from this study indicated that high maternal warmth and child positive affect during play, but not feeding interactions, are associated with reduced obesity risk from infancy to middle childhood in the context of high pre- and postnatal risks.

Deficits in executive function and suppression of default mode network in obesity

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Using a case-control design, obese individuals exhibited worse performance across a number of neurocognitive tests compared to healthy BMI controls, particularly in tasks measuring executive function.

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In a functional MRI N-Back task measuring working memory performance, obese individuals exhibited greater BOLD activity in task-negative brain regions, suggesting deficits in suppression of the default mode network (DMN).

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Obese individuals exhibited differences in cortical morphometry in frontal, temporal, and parietal regions linked to executive function.

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Integrative analyses implicated aspects of behavioral performance, inefficient DMN suppression, and cortical morphometry.

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Results suggest that obesity is associated with a diverse range of functional, structural and behavioural deficits in executive functioning; longitudinal studies are needed to clarify causal versus consequential influences.

Background

Although nutritional and metabolic factors are well established in obesity, neurocognitive determinants are less understood. Using data from the Human Connectome Project, this study concurrently investigated neurocognitive performance, neural activation during a working memory task, and cortical brain morphometry in relation to obesity in a group of young adults, 22–35 years old.

Methods

Using a case-control design, obese individuals (n = 243, body mass index [BMI] ≥ 30 kg/m²) were compared to a control group of lean BMI individuals (n = 469, BMI = 18–24.9 kg/m²). Performance tests comprised a battery of behavioral neurocognitive assessments. Neural activity was measured as blood-oxygenation-level-dependent (BOLD) activity during an N-Back task using functional magnetic resonance imaging (fMRI). Cortical morphometry included indices of volume, thickness, and surface area.

Results

Relative to the control group, the obese group exhibited significantly worse performance in terms of the National Institutes of Health Toolkit (NIH) 9-Hole Peg Board, Penn Working Memory Test, Delay Discounting, Penn Progressive Matrices, NIH Picture Vocabulary Test, Dimensional Change Card Sort Test and the in-scanner N-Back working memory test (FDR-corrected ps<0.05; ds = 0.231–0.405). The obese group also exhibited significantly greater BOLD activation in N-Back task-negative regions, including the ventromedial prefrontal cortex, posterior cingulate, and right precentral gyrus (FDR-corrected ps<0.05). Supplemental functional connectivity analyses provided evidence that the implicated regions were part of the default mode network. Significant differences in morphometry were present in the medial orbitofrontal cortex, rostral anterior cingulate cortex, inferior and superior parietal gyri, and temporal pole (FDR-corrected p<0.001). A data-driven integrative model classified 73.8% of participants correctly.

Conclusions and Relevance

This multimodal investigation suggests diverse aspects of neurocognition are associated with obesity, particularly implicating deficits in executive function and ineffective suppression of the default mode network.

Risky decision-making after exposure to a food-choice task in excess weight adolescents: Relationships with reward-related impulsivity and hunger

OBJECTIVE

To assess the effects of exposure to a food-choice task (appetizing versus healthy food) on risky decision-making by excess versus normal weight adolescents. We also analyzed the influence of food visualization on hunger levels, as well as group differences in food choices and impulsivity.

METHODS

Fifty-six adolescents (aged 13-18 years) classified as excess (n = 27) or normal (n = 29) weight participated in the study. Risky-decision-making was assessed through the Balloon Analogue Risk Task, which was administered before and after a food-choice task. We also evaluated impulsivity traits through the UPPS-P Scale, and subjective hunger levels with a visual analogue scale.

RESULTS

Adolescents with excess weight showed enhanced risky decision-making after the food-choice task compared to normal weight adolescents, as well as increased hunger levels. Furthermore, excess weight adolescents made more appetizing choices, and showed greater scores for Positive Urgency and Sensation Seeking. Reward-related impulsivity measures were positively associated with the number of appetizing choices in the food-choice task. Several associations were found between impulsivity measures, hunger levels and risk-taking variables.

CONCLUSIONS

Excess weight adolescents increased their risky-decision-making after food exposure and this augmentation was associated with the increase in hunger levels. Increased hunger levels and risk-taking after food exposure could lead to overeating. Alterations in decision-making caused by food signals may be a long-term risk factor for the development of obesity in adulthood. In modern societies, with the high availability and continuous exposure to food cues, decision-making may be a crucial factor in maintain healthy eating habits in adolescents.

Association between hedonic hunger and body-mass index versus obesity status

Obesity-associated differences in hedonic hunger, while consistently reported, have not been adequately quantified, with most studies failing to demonstrate strong correlations between Body Mass Index (BMI) and hedonic hunger indicators. Here, we quantified and assessed the nature of the relationship between hedonic hunger and BMI, in a cross-sectional study using the Portuguese version of the PFS (P-PFS) to measure hedonic hunger. Data were collected from 1266 participants belonging to non-clinical, clinical (candidates for weight-loss surgery) and population samples. Across samples, significant but weak positive associations were found between P-PFS scores and BMI, in adjusted linear regression models. However, in logistic regression models of data from the clinical and non-clinical samples, the P-PFS Food Available domain score was significantly and robustly associated with belonging to the clinical sample (OR = 1.8, 95%CI: 1.2–2.8; p = 0.008), while in the population sample it was associated to being obese (OR = 2.1, 95%CI: 1.6–2.7; p < 0.001). Thus, hedonic hunger levels are associated with obesity status with the odds of being obese approximately doubling for each unit increase in the P-PFS Food Available score.

Differential Associations of Distinct Forms of Childhood Adversity With Neurobehavioral Measures of Reward Processing: A Developmental Pathway to Depression

Childhood adversity is associated with altered reward processing, but little is known about whether this varies across distinct types of adversity. In a sample of 94 children (6-19 years), we investigated whether experiences of material deprivation, emotional deprivation, and trauma have differential associations with reward-related behavior and white matter microstructure in tracts involved in reward processing. Material deprivation (food insecurity), but not emotional deprivation or trauma, was associated with poor reward performance. Adversity-related influences on the integrity of white matter microstructure in frontostriatal tracts varied across childhood adversity types, and reductions in frontostriatal white matter integrity mediated the association of food insecurity with depressive symptoms. These findings document distinct behavioral and neurodevelopmental consequences of specific forms of adversity that have implications for psychopathology risk.

Gender Differences in Food Choice: Effects of Superior Temporal Sulcus Stimulation

The easy availability of food has caused a shift from eating for survival to hedonic eating. Women, compared to men, have shown to respond differently to food cues in the environment on a behavioral and a neural level, in particular to energy rich (compared to low energy) foods. It has been demonstrated that the right posterior superior temporal sulcus (STS) is the only region exhibiting greater activation for high vs. low calorie food choices. In order to test for a possible causal role of STS in food choice, we applied high frequency transcranial random noise stimulation (tRNS) on STS assuming a different response pattern between males and females. Our participants (18 females, 17 males) performed a forced choice task between food pairs matched for individual liking but differed in calorie, during the left STS, right STS stimulation and sham condition. Male participants showed a general preference for low calorie (LC) foods compared to females. In addition, we observed in males, but not in females, an increase of high calorie (HC) food choice during right STS tRNS compared to sham condition and left STS tRNS. Finally, we found an increase of missed choices during right STS stimulation compared to sham condition and left STS stimulation. In conclusion, thanks to tRNS evidence, we both confirm the involvement and suggest a causal role of right posterior STS in feeding behavior. Moreover, we suggest that gender differences exist in STS mechanisms underlying food choice.

Reinforcing Value of Caffeinated and Noncaffeinated Beverages After Acute Exposure in Children and Adolescents

Background: When caffeine is added to beverages, it increases beverage liking and the relative reinforcing value (RRV) of these beverages after repeated exposure. The purpose of this study was to test the hypothesis that a single acute exposure to caffeine increases liking and motivation to consume sugar-sweetened beverages (SSBs) relative to placebo. Methods: Participants were children ages 8-9 years (n = 36) and adolescents ages 15-17 years (n = 41) with an approximately equal number of boys and girls. A double-blind, placebo-controlled crossover study was conducted where participants sampled a SSB containing caffeine (1 and 2 mg/kg) on one visit and placebo (quinine 0.01 and 0.02 mg/kg) on a second visit day and then, on a third visit, played a computer game to earn points for the beverages and rated liking and taste sensations. They returned to the laboratory after a 1-week washout and had the alternate dose combination. Results: Acute exposure to the higher dose of caffeine increased the RRV of the SSB relative to placebo, but only when that dose was presented in the first week and only in female participants. The liking of the caffeine-containing SSB at the higher dose was lower than the placebo at all time points. Conclusions: These data suggest that a single exposure to a caffeinated SSB can impact its RRV and liking, but only under certain conditions and only in females. This supports previous work suggesting that caffeine can increase desire to consume SSB.

Repeatability of the infant food reinforcement paradigm: Implications of individual and developmental differences

The relative reinforcing value of food versus engagement in other behaviors may be related to the development of obesity, and interventions to reduce FRR may prevent the development of obesity. Our laboratory recently developed a paradigm to measure the reinforcing value of food versus an alternative behavior (i.e., playing with bubbles) in infants using a computerized laboratory task, during which infants press a button to earn reinforcers following a progressive ratio schedule of reinforcement. The primary purpose of this study was to examine the short-term (within 2 weeks) repeatability of this measure, specifically the outcome of infant food reinforcing ratio (FRR), or how hard infants will work for food relative to the alternative. The secondary aim was to examine whether infant age and temperament dimensions related to novelty responsiveness (high intensity pleasure and approach) moderated the repeatability of FRR. Thirty-seven infants aged 9-18 months completed this study. Repeated measures analysis of variance (ANOVA) showed no differences between time 1 and time 2 in responding for food (F = 0.463, p = 0.501), bubbles (F = 1.793, p = 0.189), or overall FRR (F = 0.797, p = 0.378). Regression models showed the association between BUB P_max at time 1 and time 2 were moderated by infant age (p = 0.04), with greater repeatability in older infants. Linear regression models also demonstrated that the infant temperamental dimension of high intensity pleasure significantly predicted BUB P_max at time 1 (β = 2.89, p = 0.01), but not at time 2. Overall, our findings support the repeatability of this measure for food portion of the reinforcement task, but demonstrated that the measure of non-food portion of the task required modification, in particular among children younger than 13 months old.

Adding a reward increases the reinforcing value of fruit

Adolescents' snack choices could be altered by increasing the reinforcing value (RV) of healthy snacks compared with unhealthy snacks. This study assessed whether the RV of fruit increased by linking it to a reward and if this increased RV was comparable with the RV of unhealthy snacks alone. Moderation effects of sex, hunger, BMI z-scores and sensitivity to reward were also explored. The RV of snacks was assessed in a sample of 165 adolescents (15·1 (sd 1·5) years, 39·4 % boys and 17·4 % overweight) using a computerised food reinforcement task. Adolescents obtained points for snacks through mouse clicks (responses) following progressive ratio schedules of increasing response requirements. Participants were (computer) randomised to three experimental groups (1:1:1): fruit (n 53), fruit+reward (n 60) or unhealthy snacks (n 69). The RV was evaluated as total number of responses and breakpoint (schedule of terminating food reinforcement task). Multilevel regression analyses (total number of responses) and Cox's proportional hazard regression models (breakpoint) were used. The total number of responses made were not different between fruit+reward and fruit (b -473; 95 % CI -1152, 205, P=0·17) or unhealthy snacks (b410; 95 % CI -222, 1043, P=0·20). The breakpoint was slightly higher for fruit than fruit+reward (HR 1·34; 95 % CI 1·00, 1·79, P=0·050), whereas no difference between unhealthy snacks and fruit+reward (HR 0·86; 95 % CI 0·62, 1·18, P=0·34) was observed. No indication of moderation was found. Offering rewards slightly increases the RV of fruit and may be a promising strategy to increase healthy food choices. Future studies should however, explore if other rewards, could reach larger effect sizes.

Daily exposure to either a high- or low-energy-dense snack food reduces its reinforcing value in adolescents

OBJECTIVE

To examine the impact of daily exposure to a low-energy-dense (LED) or a high-energy-dense (HED) snack food on its reinforcing value (RRV) in adolescents with healthy weight, overweight, or obesity.

METHODS

A parallel-group, randomized trial was used to assess RRV of LED or HED snack food at baseline and again after exposure to that snack food daily for 2 weeks in 77 adolescents, aged 13 to 17 years. Information on eating-related subject characteristics was also collected at baseline.

RESULTS

After 2 weeks of daily exposure, the RRV of the snack foods was significantly reduced in all participants, regardless of energy density or participant weight status. Among individuals who were high in dietary restraint only, those randomized to LED food found their snack food less reinforcing at baseline than those who were randomized to HED food. Baseline eating-related variables also differed as a function of weight status.

CONCLUSIONS

Daily exposure to snack food in adolescents reduces the RRV of that food regardless of snack food energy density or weight status of the adolescent. This finding differs from adults, suggesting that increases in RRV of HED food after repeated exposure may develop after adolescence.

Infant Temperament Is Associated with Relative Food Reinforcement

OBJECTIVE

Food reinforcement refers to how hard someone is motivated to work to gain access to food. Infant temperament is defined as behavioral styles, or constitutionally based individual differences in reactive and regulatory aspects of behavior. Identifying correlates of food reinforcement, such as infant temperament, may help identify infants at risk for future negative health consequences (e.g., overweight or obesity) of high food reinforcement.

METHODS

This study tested aspects of parent-reported negative reactivity and regulation and their associations with relative food reinforcement in a cross-sectional sample of 105 9- to 18-month-old infants. Hierarchical linear regression models were then used to predict infant food reinforcement for the temperament dimensions that were significantly related to it.

RESULTS

Two temperament dimensions, cuddliness (regulatory aspect) (B = -0.050, ΔR² = 0.074, p = 0.005) and rate of recovery from distress and arousal (reactive aspect) (B = -0.040, ΔR² = 0.045, p = 0.031), were inversely associated with relative food reinforcement.

CONCLUSION

Clarifying the nature of relationships between these two behavioral predictors, infant temperament and relative food reinforcement, and early obesity can elucidate the role of individual differences in early obesity risk and can further inform targets for early behavioral obesity preventive interventions.

Assessment of the motivation to use artificial sweetener among individuals with an eating disorder

Eating disorders are associated with a range of abnormalities in eating behavior. Some individuals consume large amounts of non-caloric artificial sweeteners, suggesting abnormalities in appetitive responding. The current study aimed to quantify hedonic and motivating effects of artificial sweetener in individuals with and without an eating disorder. Two laboratory studies were conducted. Hedonic preference was estimated using the number of artificial sweetener packets (0-10) added to unsweetened cherry flavored Kool-Aid (study 1). Motivation to obtain sweetener was assessed by a progressive ratio (PR) work task (study 2). Ninety-three participants (25 anorexia nervosa restricting type (AN-R), 23 AN binge/purge type (AN-B/P), 20 bulimia nervosa (BN), and 25 normal controls (NC)) completed the study. No significant difference in hedonic preference was found among participant groups. Work completed at the PR task ranged from 0 to 9500 key-board presses. The AN-B/P group had a significantly higher breakpoint and performed significantly more work for sweetener compared to the BN and NC groups. Among AN-B/P and AN-R participants, the preferred number of Equal packets was significantly correlated with the breakpoint and total work. The increased amount of work for sweetener among individuals with AN-B/P supports an enhanced reward value of sweet taste in this population, and suggests that the characteristic food avoidance in AN cannot be accounted for by decreased reward value of all taste-related stimuli. This study also supports the novel application of a PR ratio task to quantify the motivating effect of sweet taste among individuals with an eating disorder.

Energy depletion by diet or aerobic exercise alone: impact of energy deficit modality on appetite parameters

BACKGROUND

Millions of Americans attempt to lose weight each year, and it is unclear whether the modality of acute, tightly controlled energy depletions can differently affect appetite parameters and olfaction.

OBJECTIVE

The objectives were to examine how the modality of an acute 3-d isocaloric 25% energy depletion by dieting alone or by aerobic exercise alone differently affects appetite and appetite-related hormones, ad libitum feeding, food reward (snack points), and olfaction.

DESIGN

Ten male participants with a mean ± SD age of 23.7 ± 5.1 y and an initial mean ± SD body weight of 83.2 ± 11.5 kg participated in this randomized crossover design. Baseline measurement [day 1 of the control condition (CON1)] was performed and repeated 3 d later [day 4 of the control condition (CON4)], after which randomization was applied to the order of the 2 experimental conditions: 25% daily needs energy deficits induced by diet only (DIET) and by exercise only (EX) and tested before [day 1 of DIET (DIET1) and day 1 of EX (EX1)] and after 3 d [day 4 of DIET (DIET4) and day 4 of EX (EX4)] of the intervention. Body weight, leptin and ghrelin concentrations, relative-reinforcing value of food, and olfaction were measured at days 1 and 4. Body composition (dual-energy X-ray absorptiometry), ad libitum energy intake (EI; buffet), and palatability (visual analog scale) were measured only at day 4.

RESULTS

Relative to CON4, EI (P= 0.001), palatability (P= 0.01), and odor threshold (P= 0.05) were higher at DIET4; relative to CON4, palatability (P= 0.03) was higher at EX4. Compared with EX4, EI was higher for DIET4 (P= 0.006). Relative to CON4, snack points earned were higher at DIET4 (P= 0.03) and EX4 (P= 0.001); more snack points were earned at EX4 relative to DIET4 (P= 0.001).

CONCLUSIONS

Compared with the control condition, DIET represented a greater acute challenge to appetite regulation than EX, as demonstrated by greater appetite and ad libitum EI. This study confirms that compared with depletions by exercise alone, acute caloric restriction results in rapid changes in appetite that result in compensatory eating, which may initially dissuade potential success in weight-loss efforts. This trial was registered at clinicaltrials.gov as NCT02653378.

The reinforcing value of palatable snack foods and its relationship to subtypes of behavioural and self-report impulsivity

Data collected over the last decade has begun to implicate behavioural impulsivity in overeating behaviour. However, recent work has suggested that the reinforcing value of food may be associated with impulsive choice (a sub-type of impulsivity), but to date no study has examined how the reinforcing value of food relates to other aspects of impulsivity. To examine these inter-relationships, 80 women completed measures of eating (a snack intake test and the Three-Factor Eating Questionnaire and then in a separate test session an inhibitory control task, a delay discounting task, a reflection impulsivity task, and a measure of the reinforcing value of their chosen snack foods. Participants also completed the Behavioural Inhibition System/Behavioural Activation System (BIS/BAS) questionnaire to examine self-report and behavioural parallels between measures. In regression models, only Behavioural Inhibition System subscales of the BIS/BAS predicted increased responding on the reinforcing value of food task. The reinforcing value of food task predicted and trended to predict calorie and grams intake of snack foods in regression models, supporting RRV as a predictive measure of short-term snack intake. Likewise, impulsive choice and inhibitory control was not related to eating measures. Methodological implications are discussed.

Using food as reinforcer to shape children's non-food behavior: The adverse nutritional effect doubly moderated by reward sensitivity and gender

PURPOSE

Control rules are parental practices that use food, especially those high in fat or sugar, as an instrumental reinforcer to encourage children to behave in a normative manner in non-food domains. Past laboratory experiments show that repeatedly presenting snacks as a reward or associated with adults' attention, increases children's preference for the presented food. This field study aims to examine whether control rules are associated with children's increased everyday intake of food high in sugar/fat, and whether this effect is moderated by individual differences in neurobehavioral sensitivity to reward and in gender.

DESIGN

207 six- to twelve-year-old children's parents reported the children's everyday dietary intake through a food frequency questionnaire and provided information regarding the children's sensitivity to rewards as well as the frequency of enforcing control rules.

RESULTS

Children who lived in families with a high frequency of using control rules exhibited more daily fat, carbohydrate, and total energy intake than did children whose parents use control rules less often. Furthermore, the effect of control rules on dietary pattern was particularly strong for children with high reward sensitivity, especially boys.

CONCLUSIONS

Control rules have adverse consequences on children's nutrition. The moderating effects of sensitivity to reward and gender are consistent to a reinforcement learning process--associating the high-fat/sugar food consumption with social-affective pleasure resulting from performing behavior desired by parents--through which parental control rules contribute to children's maladaptive dietary patterns.

A Cognitive Profile of Obesity and Its Translation into New Interventions

Change your lifestyle: decrease your energy intake and increase your energy expenditure, is what obesity experts tell people who need to lose weight. Though the advice might be correct, it appears to be extremely difficult to change one’s lifestyle. Unhealthy habits usually are ingrained and hard to change, especially for people with an “obese cognitive profile.” Knowledge of the cognitive mechanisms that maintain unhealthy eating habits is necessary for the development of interventions that can change behavior effectively. This paper discusses some cognitive processes that might maintain unhealthy eating habits and make healthier eating difficult, like increased food cue reactivity, weak executive skills and attention bias. An effort is also done to translate these basic scientific findings into new interventions which aim to tackle the sabotaging cognitive processes. Preliminary studies into the effectiveness of these interventions, if available, are presented.

Neurobiological features of binge eating disorder

Biobehavioral features associated with binge-eating disorder (BED) have been investigated; however, few systematic reviews to date have described neuroimaging findings from studies of BED. Emerging functional and structural studies support BED as having unique and overlapping neural features as compared with other disorders. Neuroimaging studies provide evidence linking heightened responses to palatable food cues with prefrontal areas, particularly the orbitofrontal cortex (OFC), with specific relationships to hunger and reward-sensitivity measures. While few studies to date have investigated non-food-cue responses; these suggest a generalized hypofunctioning in frontostriatal areas during reward and inhibitory control processes. Early studies applying neuroimaging to treatment efforts suggest that targeting neural function underlying motivational processes may prove important in the treatment of BED.

Functional MRI of Challenging Food Choices: Forced Choice between Equally Liked High- and Low-Calorie Foods in the Absence of Hunger

We are continuously exposed to food and during the day we make many food choices. These choices play an important role in the regulation of food intake and thereby in weight management. Therefore, it is important to obtain more insight into the mechanisms that underlie these choices. While several food choice functional MRI (fMRI) studies have been conducted, the effect of energy content on neural responses during food choice has, to our knowledge, not been investigated before. Our objective was to examine brain responses during food choices between equally liked high- and low-calorie foods in the absence of hunger. During a 10-min fMRI scan 19 normal weight volunteers performed a forced-choice task. Food pairs were matched on individual liking but differed in perceived and actual caloric content (high-low). Food choice compared with non-food choice elicited stronger unilateral activation in the left insula, superior temporal sulcus, posterior cingulate gyrus and (pre)cuneus. This suggests that the food stimuli were more salient despite subject’s low motivation to eat. The right superior temporal sulcus (STS) was the only region that exhibited greater activation for high versus low calorie food choices between foods matched on liking. Together with previous studies, this suggests that STS activation during food evaluation and choice may reflect the food’s biological relevance independent of food preference. This novel finding warrants further research into the effects of hunger state and weight status on STS, which may provide a marker of biological relevance.

Blunted striatal responses to favorite-food cues in smokers

BACKGROUND

Although tobacco-smoking is associated with relatively leaner body mass and smoking cessation with weight gain, the brain mechanisms underlying these relationships are not well understood. Smokers compared to non-smokers have shown diminished neural responses to non-tobacco rewarding stimuli (e.g., monetary rewards), but brain responses to favorite-food cues have not been investigated relative to smoking status. We hypothesized that smokers would exhibit diminished neural responses compared to non-smokers in response to favorite-food cues in motivation-reward and emotion-regulating regions of the brain.

METHODS

Twenty-three smokers and 23 non-smokers matched based on body mass index (BMI), age, and gender listened to personalized favorite-food cue, stress, and neutral-relaxing audiotapes during fMRI.

RESULTS

During favorite-food cue exposure, smokers versus non-smokers exhibited diminished activations in the caudate, putamen, insula, and thalamus. Neural responses during stress and neutral-relaxing conditions were similar across groups. Subjective food-craving ratings were similar across groups.

CONCLUSIONS

The relatively diminished neural responses to favorite-food cues in smokers may contribute to lower BMI.

Factors that influence the reinforcing value of foods and beverages

Behavioral economic principles state that as the cost of a product increases, purchasing or consumption of that product will decrease. To understand the impact of behavioral economics on ingestive behavior, our laboratory utilizes an operant behavior paradigm to measure how much work an individual will engage in to get access to foods and beverages. This task provides an objective measure of the reinforcing value. We have shown that consumption of the same high fat snack food every day for two weeks reduces its reinforcing value in lean individuals, but increases its reinforcing value in a subset of obese individuals. This increase in the reinforcing value of food predicts future weight gain. Similarly, we have shown that repeated intake of caffeinated soda increases its reinforcing value in boys, but not in girls. This increase in reinforcing value is not related to usual caffeine consumption, but may be associated with positive, subjective effects of caffeine that are more likely to be reported by boys than by girls. Because food and beverage reinforcement relates to real-world consumption, it is important to determine factors that increase or decrease the reinforcing value and determine the consequences of these responses. We are especially interested in determining ways to shift the behavioral economic curve in order to develop novel strategies to decrease the reinforcing value of less healthy snack foods and beverages, such as soda, potato chips and candy and to increase the reinforcing value of healthier foods and beverages, such as water, fruits, and vegetables.

Changes in children's sleep duration on food intake, weight, and leptin

OBJECTIVE

To examine the effect of experimental changes in children's sleep duration on self-reported food intake, food reinforcement, appetite-regulating hormones, and measured weight.

METHODS

Using a within-subjects, counterbalanced, crossover design, 37 children, 8 to 11 years of age (27% overweight/obese) completed a 3-week study. Children slept their typical amount at home for 1 week and were then randomized to either increase or decrease their time in bed by 1.5 hours per night for 1 week, completing the alternate schedule on the third week. Primary outcomes were dietary intake as assessed by 24-hour dietary recalls, food reinforcement (ie, points earned for a food reward), and fasting leptin and ghrelin. The secondary outcome was child weight.

RESULTS

Participants achieved a 2 hour, 21 minute difference in the actigraph defined sleep period time between the increase and decrease sleep conditions (P < .001). Compared with the decrease sleep condition, during the increase condition, children reported consuming an average of 134 kcal/day less (P < .05), and exhibited lower fasting morning leptin values (P < .05). Measured weights were 0.22 kg lower during the increase sleep than the decrease sleep condition (P < .001). There were no differences in food reinforcement or in fasting ghrelin.

CONCLUSIONS

Compared with decreased sleep, increased sleep duration in school-age children resulted in lower reported food intake, lower fasting leptin levels, and lower weight. The potential role of sleep duration in pediatric obesity prevention and treatment warrants further study.

The effect of nucleus accumbens lesions on appetite, sexual function, and nicotine dependence in recovering heroin addicts

The nucleus accumbens (NAc) is a key part of the neural circuitry that creates reward, pleasure and motivation that facilitates human feeding, sexual and smoking behaviors. In the brain reward system, the NAc is a crucial component responsible for natural and drug-induced reinforcement behaviors. Yet it is unclear whether NAc is indispensible for all reward behaviors in human beings. The present study aimed to investigate the long-term effects of NAc ablation on sexual function, appetite, and nicotine dependence level in chronic heroin users. Eighteen former heroin-dependent patients (male) with bilateral NAc ablation via stereotactic radiofrequency surgery for alleviating drug psychological dependence were recruited. Their postoperative time ranged from 12 to 103 months. All subjects received MRI scans for assessing the accuracy of the lesion site. Evaluation of appetite, sexual function, and nicotine dependence were measured using the Simplified Nutrition Appetite Questionnaire, the Brief Sexual Function Inventory, and the Fagerström Test for Nicotine Dependence, respectively. After precluding the potential confounding variables, such as drug use (dosage and duration), post-operation duration, age, body-weight, marital status and education level, ANOVA with repeated measures revealed that the NAc ablation improved the patients’ appetite, sexual drive and sexual satisfaction. Yet there was no change in male erectile function, ejaculatory function, or nicotine dependence levels compared to the preoperative. These may suggest that although NAc is a key part of the neural circuitry, the NAc surgical lesions left the fundamental aspects of natural and drug-induced reinforcement and motivation almost intact.

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.

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.

The reinforcement-enhancing effects of nicotine: implications for the relationship between smoking, eating and weight

Concerns about body weight represent an important barrier to public health efforts aimed at reducing smoking. Epidemiological studies have found that current smokers weigh less than non-smokers, smoking cessation results in weight gain, and weight restriction is commonly cited as a reason for smoking. The mechanisms underlying the relationship between smoking and weight are complex and may involve a number of factors including changes in caloric intake, physical activity, metabolic rate, and lipogenesis. Amongst these possible mechanisms, nicotine-induced enhancement of food reinforcement may be particularly important. In this paper, we first review data from our laboratory that highlight two distinct ways in which nicotine impacts reinforced behavior: 1) by acting as a primary reinforcer; and 2) by directly (non-associatively) enhancing the reinforcing effects of other stimuli. We then elaborate on the reinforcement-enhancing effects of nicotine as they pertain to behaviors and stimuli related to food. Data from both laboratory animals and humans support the assertion that nicotine enhances the reinforcing efficacy of food and suggest that the influence of these effects on eating may be most important after nicotine cessation when nicotine's effects on satiety subside. Finally, we discuss the theoretical and clinical implications of this perspective for understanding and addressing the apparent tradeoff between smoking and weight gain. Better understanding of the mechanisms underlying the reinforcement-enhancing effects of nicotine broadly, and the effects on food reinforcement per se, may aid in the development of new treatments with better long term outcomes.