'Liking' and 'wanting' food rewards: brain substrates and roles in eating disorders

'Liking' and 'wanting' in eating and food reward: Brain mechanisms and clinical implications

It is becoming clearer how neurobiological mechanisms generate 'liking' and 'wanting' components of food reward. Mesocorticolimbic mechanisms that enhance 'liking' include brain hedonic hotspots, which are specialized subregions that are uniquely able to causally amplify the hedonic impact of palatable tastes. Hedonic hotspots are found in nucleus accumbens medial shell, ventral pallidum, orbitofrontal cortex, insula cortex, and brainstem. In turn, a much larger mesocorticolimbic circuitry generates 'wanting' or incentive motivation to obtain and consume food rewards. Hedonic and motivational circuitry interact together and with hypothalamic homeostatic circuitry, allowing relevant physiological hunger and satiety states to modulate 'liking' and 'wanting' for food rewards. In some conditions such as drug addiction, 'wanting' is known to dramatically detach from 'liking' for the same reward, and this may also occur in over-eating disorders. Via incentive sensitization, 'wanting' selectively becomes higher, especially when triggered by reward cues when encountered in vulnerable states of stress, etc. Emerging evidence suggests that some cases of obesity and binge eating disorders may reflect an incentive-sensitization brain signature of cue hyper-reactivity, causing excessive 'wanting' to eat. Future findings on the neurobiological bases of 'liking' and 'wanting' can continue to improve understanding of both normal food reward and causes of clinical eating disorders.

Prevalence of obesity among U.S. population with substance dependence

AIM

To investigate associations between substance dependence and obesity.

METHODS

Obesity (body mass index ≥ 30 kg/m²) status and the status of dependence on heroin, stimulant, marijuana, nicotine and alcohol (past-month status for nicotine and past-year status for all others) were identified from the U.S. National Survey on Drug Use and Health (NSDUH, 2015-2017) datasets. SAS Surveylogistic regression was used to estimate adjusted odds ratio (AOR) for the association between each substance dependence and obesity, adjusting for potentially confounding effects of sociodemographic factors and health condition.

RESULTS

It was estimated that 10.6 % of noninstitutional U.S. residents aged 12 years or older were nicotine-dependent, 3.0 % alcohol-dependent, 1.0 % marijuana-dependent, 0.6 % stimulant-dependent, and 0.2 % heroin-dependent. Heroin-dependent individuals had 59 % lower odds of obesity relative to their non-dependent counterparts (AOR = 0.41; 95 % CI: 0.28-0.60; p < 0.0001). Lower odds of obesity were also noted for marijuana-dependent (AOR = 0.64; 95 % CI: 0.56-0.73; p < 0.0001), nicotine-dependent (AOR = 0.68; 95 % CI: 0.64-0.72; p < 0.0001) and alcohol-dependent (AOR = 0.77, 95 % CI: 0.69-0.84; p < 0.0001) individuals, but not statistically significant for stimulant-dependent individuals (AOR = 0.84; 95 % CI: 0.68-1.02; p = 0.0825).

CONCLUSIONS

Heroin, marijuana, nicotine and alcohol dependence were associated with lower odds of obesity than their non-dependence counterparts. Main findings based on 2015-2017 NSDUH are consistent with findings from our prior report based on clinical trials data from National Institute on Drug Abuse Clinical Trials Network, and other epidemiological evidence in the literature. These findings can alert substance abuse treatment professionals to monitor weight change, especially among weight-concerned substance abusers.

How do patients with eating disorders perceive and evaluate food portion sizes? A systematic review

OBJECTIVE

The selection of adequate portion sizes plays a key role in the nutritional treatment of eating disorders (EDs). There is limited knowledge concerning the estimation of portion sizes in individuals with EDs.

METHOD

We performed a systematic review according to the PRISMA statement to synthesise current evidence in this field. Of N = 584 hits, four full-texts were included in the qualitative synthesis.

RESULTS

While patients with anorexia nervosa (AN) tend to overestimate the size of energy-dense food items and small to medium sized meal portions, they do not show a different estimation compared to healthy controls when judging the amount of food pieces. Large portion sizes were associated with increased anxiety in patients with AN.

DISCUSSION

The overestimation of food portion sizes seems to be driven by attitudinal and/or higher cognitive factors associated with AN. Differences between the studies are discussed and suggestions for future studies are given.

Neural Indicators Of Food Cue Reactivity, Regulation, And Valuation And Their Associations With Body Composition And Daily Eating Behavior

Exposure to food cues activates the brain's reward system and undermines efforts to regulate impulses to eat. During explicit regulation, lateral prefrontal cortex activates and modulates activity in reward regions and decreases food cravings. However, it is unclear the extent to which between-person differences in recruitment of regions associated with reward processing, subjective valuation, and regulation during food cue exposure-absent instructions to regulate-predict body composition and daily eating behaviors. In this preregistered study, we pooled data from five fMRI samples (N = 262) to examine whether regions associated with reward, valuation, and regulation, as well as whole-brain pattern expression indexing these processes, were recruited during food cue exposure and associated with body composition and real-world eating behavior. Regression models for a single a priori analytic path indicated that univariate and multivariate measures of reward and valuation were associated with individual differences in BMI and enactment of daily food cravings. Specification curve analyses further revealed reliable associations between univariate and multivariate neural indicators of reactivity, regulation, and valuation, and all outcomes. These findings highlight the utility of these methods to elucidate brain-behavior associations and suggest that multiple processes are implicated in proximal and distal markers of eating behavior.

Brain Activity Associated With Regulating Food Cravings Predicts Changes in Self-Reported Food Craving and Consumption Over Time

Neural patterns associated with viewing energy-dense foods can predict changes in eating-related outcomes. However, most research on this topic is limited to one follow-up time point, and single outcome measures. The present study seeks to add to that literature by employing a more refined assessment of food craving and consumption outcomes along with a more detailed neurobiological model of behavior change over several time points. Here, a community sample of 88 individuals (age: M = 39.17, SD = 3.47; baseline BMI: M = 31.5, SD = 3.9, range 24–42) with higher body mass index (BMI) performed a food craving reactivity and regulation task while undergoing functional magnetic resonance imaging. At that time—and 1, 3, and 6 months later—participants reported craving for and consumption of healthy and unhealthy foods via the Food Craving Inventory (FCI) and ASA24 (N at 6 months = 52–55 depending on the measure). A priori hypotheses that brain activity associated with both viewing and regulating personally desired unhealthy, energy-dense foods would be associated with self-reported craving for and consumption of unhealthy foods at baseline were not supported by the data. Instead, regression models controlling for age, sex, and BMI demonstrated that brain activity across several regions measured while individuals were regulating their desires for unhealthy food was associated with the self-reported craving for and consumption of healthy food. The hypothesis that vmPFC activity would predict patterns of healthier eating was also not supported. Instead, linear mixed models controlling for baseline age and sex, as well as changes in BMI, revealed that more regulation-related activity in the dlPFC, dACC, IFG, and vmPFC at baseline predicted decreases in the craving for and consumption of healthy foods over the course of 6 months.

Food-related attentional bias and its associations with appetitive motivation and body weight: A systematic review and meta-analysis

Theoretical models suggest that food-related visual attentional bias (AB) may be related to appetitive motivational states and individual differences in body weight; however, findings in this area are equivocal. We conducted a systematic review and series of meta-analyses to determine if there is a positive association between food-related AB and: (1.) body mass index (BMI) (number of effect sizes (k) = 110), (2.) hunger (k = 98), (3.) subjective craving for food (k = 35), and (4.) food intake (k = 44). Food-related AB was robustly associated with craving (r = 0.134 (95% CI 0.061, 0.208); p < .001), food intake (r = 0.085 (95% CI 0.038, 0.132); p < .001), and hunger (r = 0.048 (95% CI 0.016, 0.079); p = .003), but these correlations were small. Food-related AB was unrelated to BMI (r = 0.008 (95% CI -0.020, 0.035); p = .583) and this result was not moderated by type of food stimuli, method of AB assessment, or the subcomponent of AB that was examined. Furthermore, in a between-groups analysis (k = 22) which directly compared participants with overweight/obesity to healthy-weight control groups, there was no evidence for an effect of weight status on food-related AB (Hedge's g = 0.104, (95% CI -0.050, 0.258); p = .186). Taken together, these findings suggest that food-related AB is sensitive to changes in the motivational value of food, but is unrelated to individual differences in body weight. Our findings question the traditional view of AB as a trait-like index of preoccupation with food and have implications for novel theoretical perspectives on the role of food AB in appetite control and obesity.

Love at first taste: Activation in reward-related brain regions during single-trial naturalistic appetitive conditioning in humans

Palatable food can trigger appetitive responses, such as salivation and approach tendencies. Though evolutionarily functional, these conditioned responses can encourage overeating and obesity when food is abundant. The current study examines the neural correlates of 'denovo' Pavlovian appetitive conditioning, pairing one class of unknown objects (conditioned stimuli, CS) with their sweet taste (unconditioned stimulus, US) during a single trial. To do so, 23 participants consumed unknown (marzipan) objects of one particular color (CS+) while only interacting with control stimuli of different color and shape (CS-). After this single-trial conditioning procedure, participants viewed and rated images of the marzipan figures and the control objects during functional magnetic resonance imaging (fMRI). Relative to the CS-, the CS+ elicited stronger activation in the dorsal striatum, a brain region associated with cue-reward coupling. Furthermore, conditioning effects in subjective 'craving', defined as increased palatability and desire to eat, were observed, and these were positively related to conditioning effects in the amygdala, a brain region associated with the need-dependent value of a reward. Thus, the study identified reward-related brain regions involved in single-trial appetitive learning, thereby providing a potential mechanism that contributes to the etiology of food craving. These findings might help to understand clinically relevant food cravings in individuals with eating or weight related concerns and might support the development of extinction based treatments.

High-fat food biases hypothalamic and mesolimbic expression of consummatory drives

Maintaining healthy body weight is increasingly difficult in our obesogenic environment. Dieting efforts are often overpowered by the internal drive to consume energy-dense foods. Although the selection of calorically rich substrates over healthier options is identifiable across species, the mechanisms behind this choice remain poorly understood. Using a passive devaluation paradigm, we found that exposure to high-fat diet (HFD) suppresses the intake of nutritionally balanced standard chow diet (SD) irrespective of age, sex, body mass accrual and functional leptin or melanocortin-4 receptor signaling. Longitudinal recordings revealed that this SD devaluation and subsequent shift toward HFD consumption is encoded at the level of hypothalamic agouti-related peptide neurons and mesolimbic dopamine signaling. Prior HFD consumption vastly diminished the capacity of SD to alleviate the negative valence associated with hunger and the rewarding properties of food discovery even after periods of HFD abstinence. These data reveal a neural basis behind the hardships of dieting.

Asociación entre el sistema de recompensa del cerebro y elección de comida en adultos mayores y de mediana edad

Introducción. Todos los días las personas toman diferentes decisiones relacionadas con su elección de alimentos, lo que a su vez determina sus hábitos alimenticios. El sistema de recompensa del cerebro (SRC) permite asociar ciertas situaciones con una sensación de placer, lo que influye en la posterior elección de alimentos.Objetivo. Describir cómo influye el SRC en el proceso de elección de comida en adultos de mediana edad y en adultos mayores autosuficientes.Materiales y métodos. Se realizó una búsqueda de la literatura en PubMed y SciELO. Se buscaron artículos escritos en inglés y español y publicados entre 1996 y 2018 utilizando los siguientes términos (en ambos idiomas): ”elección de la comida”, “sistema de recompensa”, “nutrición”, “adulto”, “adulto mayor”, “estado nutricional” y “envejecimiento”.Resultados. 50 artículos cumplieron con los criterios de inclusión. Solo 1 estudio estaba escrito en español; 22 fueron realizados en adultos mayores y el resto en adultos entre 20 y 40 años.Conclusiones. Teniendo en cuenta el escaso número de estudios sobre la conducta alimentaria en general, y en particular sobre la elección de comida en adultos mayores y de mediana edad, es necesario realizar más estudios en Latinoamérica sobre los procesos que subyacen al SRC y su relación con la elección de comida, y cómo estos cambian con la edad para predecir posibles conductas alimentarias e implementar intervenciones efectivas, pues una dieta saludable es esencial para un envejecimiento saludable.

Hungry for colours? Attentional bias for food crucially depends on perceptual information

Attentional bias has been consistently investigated with both threatening and rewarding stimuli, such as food. Several studies demonstrated the presence of an attentional bias for high-calorie food cues compared to neutral (non-food) cues. Authors have interpreted this effect in the context of top-down processes (e.g. the food draws attention thanks to the experience we have with it). The aim of the present study is to test whether perceptual features (bottom-up processes) can modulate the attentional bias effect of food stimuli. Using a dot-probe task, we investigated the relevance of colours in the occurrence of the attentional bias. We compared two different categories of naturalistic food images (high-calorie versus low-calorie) both coloured (Exp. 1) and greyscale (Exp. 2). While we found the occurrence of the attentional bias with high-calorie food coloured images, we did not obtain any significant differences with greyscale images. In Experiments 3 and 4, we compared greyscale office items images, respectively, with greyscale high-calorie food images (Exp. 3) and greyscale low-calorie food images (Exp. 4). In both these last experiments, we did not find any attentional bias. Thus, taken together, our results show that colours convey crucial identity information that could orient our attention. We interpret these results as linked to the relevance of visual appearance in our experience of food.

Prevention of adolescent obesity: The global picture and an indian perspective

BACKGROUND AND AIMS

Adolescent obesity is an increasing health burden with a growing prevalence in low- and middle-income countries. The aim of this review is to assess and compare current best practice obesity prevention interventions for adolescents in developed nations and in India METHODS: Medline (PubMed), CINAHL, Scopus and Google Scholar electronic databases from 2000 to 2020 were searched using the key terms obesity, overweight, child and adolescent obesity, child and adolescent overweight, interventions for childhood and adolescent obesity and dietary interventions for adolescents, developed countries, and India.

RESULTS

Developed nations worldwide have formed and implemented policies and programs at national and local levels to attempt to minimize and manage adolescent obesity. In 2019, scientific and government consultation groups in India have recommended national cross-sectoral structures to action interventions to restrict high-fat food intake, increase physical activity in children and adolescents and to link current research and school-based interventions in a national framework.

CONCLUSIONS

Obesity is a multifactorial problem, and multimodal interventions involving all Indian stakeholders, combined with government policy reform, are urgently needed.

Reciprocal interactions between sodium appetite and need-free sugar intake

Behavioral sensitization occurs during sodium appetite (expressed as sodium intake to compensate for depleted sodium) and need-free sodium intake (expressed as daily overnight sodium intake in excess of dietary sodium need). Previously, we found that a slow-onset sodium appetite protocol cross-sensitized need-free sucrose intake in sucrose-naïve adult rats. That is, a history of sodium depletion elevated later sucrose intake. The objective of the present work was, first, to investigate whether a protocol that evokes a rapid-onset (within 2 h) sodium appetite using furosemide along with a low dose captopril (Furo/Cap), also cross-sensitizes sucrose intake. Then, we investigated whether 1) sensitization of need-free 0.3 M NaCl intake interacts with need-free sucrose intake, and 2) MK-801, a glutamate NMDA receptor antagonist, inhibits cross-sensitization of sucrose intake. Groups received 3-4 Furo/Cap or vehicle treatments with 48/72-h intervals. We investigated sucrose intake in hydrated and fed conditions for 2 h/day for 5 days, starting 6-10 days after the last Furo/Cap treatment. Episodes of Furo/Cap sensitized need-free sodium intake, as expected. Similar to our prior work, the rapid-onset Furo/Cap protocol cross-sensitized sucrose intake in sucrose-naïve rats and had no persistent effect on blood biochemistry. MK-801 treatment along with Furo/Cap injections appeared to prevent cross-sensitization of sucrose consumption. Sucrose intake tests unexpectedly reduced sensitized need-free sodium intake. However, MK-801 treatment allowed a rebound in need-free sodium intake subsequent to the last sucrose intake test. The results suggest that plasticity in glutamatergic mechanisms mediate inverse and reciprocal interactions between the production of sodium appetite and sucrose intake.

Influence of hunger on attentional engagement with and disengagement from pictorial food cues in women with a healthy weight

Because of inconsistencies in the field of attentional bias to food cues in eating behavior, this study aimed to re-examine the assumption that hungry healthy weight individuals have an attentional bias to food cues, but satiated healthy weight individuals do not. Since attentional engagement and attentional disengagement have been proposed to play a distinct role in behavior, we used a performance measure that is specifically designed to differentiate between these two attentional processes. Participants were healthy weight women who normally eat breakfast. In the satiated condition (n = 54), participants were instructed to have breakfast just before coming to the lab. In the fasted condition (n = 50), participants fasted on average 14 h before coming into the lab. Satiated women showed no stronger attentional engagement or attentional disengagement bias to food cues than to neutral cues. Fasted women did show stronger attentional engagement to food cues than to neutral cues that were shown briefly (100 ms). They showed no bias in attentional engagement to food cues that were shown longer (500 ms) or in attentional disengagement from food cues. These findings are in line with the assumption that healthy weight individuals show an attentional bias to food cues when food stimuli are motivationally salient. Furthermore, the findings point to the importance of differentiating between attentional engagement and attentional disengagement.

Endogenous opioids facilitate intrinsically-rewarded birdsong

Many songbirds sing in non-reproductive contexts while in flocks. Singing in such gregarious contexts is critical for maintaining and learning songs; however, song is not directed towards other individuals and has no obvious, immediate social consequences. Studies using conditioned place preference (CPP) tests of reward indicate that song production in gregarious contexts correlates positively with a bird’s intrinsic reward state and with opioid markers in the medial preoptic nucleus (mPOA). However, the causal involvement of opioids in gregarious song is unknown. Here we report that the selective mu opioid receptor (MOR) agonist fentanyl dose-dependently facilitates gregarious song and reduces stress/anxiety-related behavior in male and female European starlings. Furthermore, infusion of siRNA targeting MORs specifically in mPOA both suppresses gregarious song and disrupts the positive association between affective state and singing behavior, as revealed using CPP tests of song-associated reward. Results strongly implicate opioids in gregarious song and suggest that endogenous opioids in the mPOA may facilitate song by influencing an individual’s intrinsic reward state.

Appetite changes reveal depression subgroups with distinct endocrine, metabolic, and immune states

There exists little human neuroscience research to explain why some individuals lose their appetite when they become depressed, while others eat more. Answering this question may reveal much about the various pathophysiologies underlying depression. The present study combined neuroimaging, salivary cortisol, and blood markers of inflammation and metabolism collected prior to scanning. We compared the relationships between peripheral endocrine, metabolic, and immune signaling and brain activity to food cues between depressed participants experiencing increased (N = 23) or decreased (N = 31) appetite and weight in their current depressive episode and healthy control participants (N = 42). The two depression subgroups were unmedicated and did not differ in depression severity, anxiety, anhedonia, or body mass index. Depressed participants experiencing decreased appetite had higher cortisol levels than subjects in the other two groups, and their cortisol values correlated inversely with the ventral striatal response to food cues. In contrast, depressed participants experiencing increased appetite exhibited marked immunometabolic dysregulation, with higher insulin, insulin resistance, leptin, CRP, IL-1RA, and IL-6, and lower ghrelin than subjects in other groups, and the magnitude of their insulin resistance correlated positively with the insula response to food cues. These findings provide novel evidence linking aberrations in homeostatic signaling pathways within depression subtypes to the activity of neural systems that respond to food cues and select when, what, and how much to eat. In conjunction with prior work, the present findings strongly support the existence of pathophysiologically distinct depression subtypes for which the direction of appetite change may be an easily measured behavioral marker.

Stimuli predicting high-calorie reward increase dopamine release and drive approach to food in the absence of homeostatic need

Animals and humans are motivated to consume high-fat, high-calorie foods by cues predicting such foods. The neural mechanisms underlying this effect are not well understood.Objective: We tested the hypothesis that cues paired with a food reward, as compared to explicitly unpaired cues, increase rats' food-seeking behavior by potentiating dopamine release in the nucleus accumbens, and that this effect would be less evident under satiety.Methods: We used a simple discriminative stimulus task and electrochemical recordings of dopamine release in freely moving rats.Results: We found that both food-predictive cue and hunger increased conditioned approaches to the receptacle (food-seeking behavior indicated by movement to the food receptacle). In addition, we observed dopamine release when the food-predictive cue (but not the unpaired cue) was presented, independent of hunger or satiety. Finally, we found a positive correlation between dopamine release amplitude and the number of conditioned approaches to the food receptacle in the sated condition, but not in the hungry condition.Discussion: Our results suggest that dopamine could drive seeking behavior for calorie-dense food in absence of homeostatic need, a core aspect of binge eating disorders.

Investigating resting brain perfusion abnormalities and disease target-engagement by intranasal oxytocin in women with bulimia nervosa and binge-eating disorder and healthy controls

Advances in the treatment of bulimia nervosa and binge-eating disorder (BN/BED) have been marred by our limited understanding of the underpinning neurobiology. Here we measured regional cerebral blood flow (rCBF) to map resting perfusion abnormalities in women with BN/BED compared with healthy controls and investigate whether intranasal oxytocin (OT), proposed as a potential treatment, can restore perfusion in disorder-related brain circuits. Twenty-four women with BN/BED and 23 healthy women participated in a randomized, double-blind, crossover, placebo-controlled study. We used arterial spin labelling MRI to measure rCBF and the effects of an acute dose of intranasal OT (40 IU) or placebo over 18-26 min post dosing, as we have previously shown robust OT-induced changes in resting rCBF in men in a similar time-window (15-36 min post dosing). We tested for effects of treatment, diagnosis and their interaction on extracted rCBF values in anatomical regions-of-interest previously implicated in BN/BED by other neuroimaging modalities, and conducted exploratory whole-brain analyses to investigate previously unidentified brain regions. We demonstrated that women with BN/BED presented increased resting rCBF in the medial prefrontal and orbitofrontal cortices, anterior cingulate gyrus, posterior insula and middle/inferior temporal gyri bilaterally. Hyperperfusion in these areas specifically correlated with eating symptoms severity in patients. Our data did not support a normalizing effect of intranasal OT on perfusion abnormalities in these patients, at least for the specific dose (40 IU) and post-dosing interval (18-26 min) examined. Our findings enhance our understanding of resting brain abnormalities in BN/BED and identify resting rCBF as a non-invasive potential biomarker for disease-related changes and treatment monitoring. They also highlight the need for a comprehensive investigation of intranasal OT pharmacodynamics in women before we can fully ascertain its therapeutic value in disorders affecting predominantly this gender, such as BN/BED.

A Systematic Review and Activation Likelihood Estimation Meta-Analysis of fMRI Studies on Sweet Taste in Humans

BACKGROUND

The reward value of palatable foods is often cited as an important influence on eating behaviors, including intake of sugars. However, human neuroimaging studies have generated conflicting evidence on the basic neural representation of taste and reward responses to caloric sweeteners (sucrose and glucose), and most relevant studies have used small subject numbers.

OBJECTIVE

We conducted a systematic review and a coordinate-based meta-analysis of studies reporting brain responses to oral sugar solutions.

METHODS

A systematic search of MEDLINE, Scopus, and PsycINFO through October 2019 identified fMRI studies (in healthy human adults, including those with overweight or obesity) assessing differences in responses to purified sweet and nonsweet taste stimuli. Data were extracted with the primary objective of quantifying evidence for the activation of brain regions associated with caloric sweet taste sensation. We used activation likelihood estimation meta-analysis methods. We also performed multiple sensitivity analyses to assess the generality of effects.

RESULTS

Of 455 unique articles, 15 met the criteria for inclusion. These contributed to 2 primary meta-analyses: 1) sucrose (13 experiments, 179 coordinates, n = 241) and 2) sucrose + glucose (16 experiments, 209 coordinates, n = 262). Consistent activation was apparent in primary taste areas: insula (69.2% of studies) and opercular cortex (76.9% of studies), precentral gyri (53.9% of studies), and globus pallidus and postcentral gyrus (30.8% of studies for each). Evidence of reward activity (caudate) was seen in the primary analyses (30.8% of studies) but not in sensitivity analysis.

CONCLUSIONS

We confirm the importance of primary taste areas for gustatory processing in human adults. We also provide tentative evidence for reward-related caudate activity in relation to the sweet taste of caloric sugars. A number of factors affect the observation and interpretation of brain responses, including reward-related activity. Firm conclusions require confirmation with large data set studies.

Homeostatic regulation of reward via synaptic insertion of calcium-permeable AMPA receptors in nucleus accumbens

The incentive effects of food and related cues are determined by stimulus properties and the internal state of the organism. Enhanced hedonic reactivity and incentive motivation in energy deficient subjects have been demonstrated in animal models and humans. Defining the neurobiological underpinnings of these state-based modulatory effects could illuminate fundamental mechanisms of adaptive behavior, as well as provide insight into maladaptive consequences of weight loss dieting and the relationship between disturbed eating behavior and substance abuse. This article summarizes research of our laboratory aimed at identifying neuroadaptations induced by chronic food restriction (FR) that increase the reward magnitude of drugs and associated cues. The main findings are that FR decreases basal dopamine (DA) transmission, upregulates signaling downstream of the D1 DA receptor (D1R), and triggers synaptic incorporation of calcium-permeable AMPA receptors (CP-AMPARs) in the nucleus accumbens (NAc). Selective antagonism of CP-AMPARs decreases excitatory postsynaptic currents in NAc medium spiny neurons of FR rats and blocks the enhanced rewarding effects of d-amphetamine and a D1R, but not a D2R, agonist. These results suggest that FR drives CP-AMPARs into the synaptic membrane of D1R-expressing MSNs, possibly as a homeostatic response to reward loss. FR subjects also display diminished aversion for contexts associated with LiCl treatment and centrally infused cocaine. An encompassing, though speculative, hypothesis is that NAc synaptic incorporation of CP-AMPARs in response to food scarcity and other forms of sustained reward loss adaptively increases incentive effects of reward stimuli and, at the same time, diminishes responsiveness to aversive stimuli that have potential to interfere with goal pursuit.

Prefrontal cortex is associated with the rapid onset of parental behavior in inexperienced adult mice (C57BL/6)

There is significant variability in the immediate behavioral response displayed by inexperienced adult mice when exposed to pups for the first time. The aim of this study was to determine which brain regions were engaged (higher c-Fos-immunoreactivity, c-Fos-ir) when virgin females, that were exposed to pups for 15 or 60 min, displayed full parental behavior (FPB), partial parental behavior (PPB), or non-parental behavior (NPB), or virgin males displayed PPB or infanticidal behavior (IB). The number of c-Fos-ir neurons in the prelimbic cortex (PL) was higher in parental females than in the NPB group (after a 15-min exposure), and the group not exposed to pups (NE). C-Fos expression in the nucleus accumbens (NA) was increased in most groups of females exposed to pups compared to NE. Higher c-Fos-ir was also found in the shell subregion of the NA in infanticidal males, compared to males NE. The cortical (CoA) and medial (MA) amygdala also showed higher c-Fos-ir in parental females compared to NE animals. However, PPB and IB male groups also exhibited higher c-Fos-ir in the CoA and MA compared to the NE group. The expression of c-Fos in the different subregions of medial preoptic area and the ventromedial nucleus of the hypothalamus was not specifically associated with either parental or infanticidal behavior. No brain activation in males was specifically associated with infanticidal behavior. Our results suggest that 15 min of exposure to pups is enough to detect brain regions associated with parental behavior (PL) or pups processing (NA, MA, CoA) in mice. The PL might participate in the immediate onset of parental behavior in virgin females, coordinating and planning its rapid execution.

Mitochondrial uncoupler BAM15 reverses diet-induced obesity and insulin resistance in mice

Obesity is a health problem affecting more than 40% of US adults and 13% of the global population. Anti-obesity treatments including diet, exercise, surgery and pharmacotherapies have so far failed to reverse obesity incidence. Herein, we target obesity with a pharmacotherapeutic approach that decreases caloric efficiency by mitochondrial uncoupling. We show that a recently identified mitochondrial uncoupler BAM15 is orally bioavailable, increases nutrient oxidation, and decreases body fat mass without altering food intake, lean body mass, body temperature, or biochemical and haematological markers of toxicity. BAM15 decreases hepatic fat, decreases inflammatory lipids, and has strong antioxidant effects. Hyperinsulinemic-euglycemic clamp studies show that BAM15 improves insulin sensitivity in multiple tissue types. Collectively, these data demonstrate that pharmacologic mitochondrial uncoupling with BAM15 has powerful anti-obesity and insulin sensitizing effects without compromising lean mass or affecting food intake.

Post-Ingestive Sensations Driving Post-Ingestive Food Pleasure: A Cross-Cultural Consumer Study Comparing Denmark and China

Culture is one of the main factors that influence food assessment. This cross-cultural research aimed to compare Chinese and Danish consumers in their post-ingestive drivers of Post-Ingestive Food Pleasure (PIFP). We define PIFP as a “subjective conscious sensation of pleasure and joy experienced after eating”. We conducted two in-country consumer studies in Denmark (n = 48) and in China (n = 53), measuring post-ingestive sensations and PIFP using visual analogue scale, for three hours following consumption of a breakfast meal. Key results revealed perceived Satisfaction, Mental, Overall and Physical wellbeing to be highly influential on PIFP in both countries. Moreover, Danish consumers perceived appetite-related sensations such as Satiety, Hunger, Desire-to-eat and In-need-of-food to be influential on PIFP, which was not the case in China. In China, more vitality-related sensations such as Energized, Relaxation and Concentration were found to be drivers of PIFP. These results suggest similarities but also distinct subtleties in the cultural constructs of PIFP in Denmark and in China. Focusing on Food Pleasure as a post-ingestive measure provides valuable output, deeper insights into what drives Food Pleasure, and, importantly, takes us beyond the processes only active during the actual eating event.

The use of the orbitofrontal H-sulcus as a reference frame for value signals

Understanding the factors that drive organization and function of the brain is an enduring question in neuroscience. Using functional magnetic resonance imaging (fMRI), structure and function have been mapped in primary sensory cortices based on knowledge of the organizational principles that likely drive a given region (e.g., aspects of visual form in primary visual cortex and sound frequency in primary auditory cortex) and knowledge of underlying cytoarchitecture. The organizing principles of higher-order brain areas that encode more complex signals, such as the orbitofrontal cortex (OFC), are less well understood. One fundamental component that underlies the many functions of the OFC is the ability to compute the reward or value of a given object. There is evidence of variability in the spatial location of responses to specific categories of objects (or value of said objects) within the OFC, and several reference frames have been proposed to explain this variability, including topographic spatial gradients that correspond to axes of primary versus secondary rewards and positive versus negative reinforcers. One potentially useful structural morphometric reference frame in the OFC is the "H-sulcus," a pattern formed by medial orbital, lateral orbital and transverse orbital sulci. In 48 human subjects, we use a structural morphometric tracing procedure to localize functional activation along the H-sulcus for face and food stimuli. We report the novel finding that food-selective responses are consistently found within the caudal portion of the medial orbital sulcus, but no consistency within the H-sulcus for response to face stimuli. These results suggest that sulcogyral anatomy of the H-sulcus may be an important morphological metric that contributes to the organizing principles of the OFC response to certain stimulus categories, including food.

Laboratory-based interventions targeting food craving: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to quantify the effects of laboratory-based interventions targeting specific mechanisms of food craving, to identify moderators of effects, and to qualitatively summarize findings. The study was conducted and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Sixty-nine studies were included in the quantitative synthesis, and separate meta-analyses were conducted for the outcomes self-reported craving and objective food intake. Results show small to medium positive effects across specific craving interventions on both outcomes. Effect sizes were partly moderated by intervention type. The most effective intervention regarding food intake was in sensu cue exposure. For subjective craving, the most robust evidence was found for beneficial effects of cognitive regulation strategies (ie, reappraisal, suppression, and distraction). Results further indicate that training inhibitory control through behavioral inhibition might be more effective than approach-avoidance training when considering its effect on subjective craving and food intake. People with external eating habits, overeating, or loss-of-control eating might benefit from these types of specific craving interventions. Future research should focus on long-term effects, transferability, and effectiveness in clinical samples.

Neurovegetative symptom subtypes in young people with major depressive disorder and their structural brain correlates

Depression is a leading cause of burden of disease among young people. Current treatments are not uniformly effective, in part due to the heterogeneous nature of major depressive disorder (MDD). Refining MDD into more homogeneous subtypes is an important step towards identifying underlying pathophysiological mechanisms and improving treatment of young people. In adults, symptom-based subtypes of depression identified using data-driven methods mainly differed in patterns of neurovegetative symptoms (sleep and appetite/weight). These subtypes have been associated with differential biological mechanisms, including immuno-metabolic markers, genetics and brain alterations (mainly in the ventral striatum, medial orbitofrontal cortex, insular cortex, anterior cingulate cortex amygdala and hippocampus). K-means clustering was applied to individual depressive symptoms from the Quick Inventory of Depressive Symptoms (QIDS) in 275 young people (15-25 years old) with MDD to identify symptom-based subtypes, and in 244 young people from an independent dataset (a subsample of the STAR*D dataset). Cortical surface area and thickness and subcortical volume were compared between the subtypes and 100 healthy controls using structural MRI. Three subtypes were identified in the discovery dataset and replicated in the independent dataset; severe depression with increased appetite, severe depression with decreased appetite and severe insomnia, and moderate depression. The severe increased appetite subtype showed lower surface area in the anterior insula compared to both healthy controls. Our findings in young people replicate the previously identified symptom-based depression subtypes in adults. The structural alterations of the anterior insular cortex add to the existing evidence of different pathophysiological mechanisms involved in this subtype.

Circulating Triglycerides Gate Dopamine-Associated Behaviors through DRD2-Expressing Neurons

Energy-dense food alters dopaminergic (DA) transmission in the mesocorticolimbic (MCL) system and can promote reward dysfunctions, compulsive feeding, and weight gain. Yet the mechanisms by which nutrients influence the MCL circuitry remain elusive. Here, we show that nutritional triglycerides (TGs), a conserved post-prandial metabolic signature among mammals, can be metabolized within the MCL system and modulate DA-associated behaviors by gating the activity of dopamine receptor subtype 2 (DRD2)-expressing neurons through a mechanism that involves the action of the lipoprotein lipase (LPL). Further, we show that in humans, post-prandial TG excursions modulate brain responses to food cues in individuals carrying a genetic risk for reduced DRD2 signaling. Collectively, these findings unveil a novel mechanism by which dietary TGs directly alter signaling in the reward circuit to regulate behavior, thereby providing a new mechanistic basis by which energy-rich diets may lead to (mal)adaptations in DA signaling that underlie reward deficit and compulsive behavior.

ERP and oscillatory differences in overweight/obese and normal-weight adolescents in response to food stimuli

BACKGROUND

Findings are mixed regarding the association of electroencephalographic (EEG) attentional bias measures and body weight, with few studies measuring food craving or intake and no study reporting oscillatory measures.

METHODS

EEG data were collected while 28 satiated adolescents (14 overweight/obese) viewed pictures of neutral, low-calorie food, and high-calorie food stimuli and rated their desire to eat, before having access to high-calorie snacks.

RESULTS

Unlike normal-weight adolescents, overweight/obese participants showed similar P300 amplitudes for high- and low-calorie food, and strongest event-related alpha band desynchronization for low-calorie stimuli. P300 amplitudes and state craving for low-calorie food furthermore predicted snack intake in this group.

CONCLUSIONS

The current research focus in overweight/obesity might need to be extended to include low-calorie food. While all participants showed an attentional bias for high-calorie food, it was the processing of low-calorie food which distinguished the two weight groups on measures of neural activity and which was associated with snack food intake in the overweight/obese group.

Food, Eating, and the Gastrointestinal Tract

Food ingestion induces a metered response of the digestive system. Initially, the upper digestive system reacts to process and extract meal substrates. Later, meal residues not absorbed in the small bowel, pass into the colon and activate the metabolism of resident microbiota. Food consumption also induces sensations that arise before ingestion (e.g., anticipatory reward), during ingestion (e.g., gustation), and most importantly, after the meal (i.e., the postprandial experience). The postprandial experience involves homeostatic sensations (satiety, fullness) with a hedonic dimension (digestive well-being, mood). The factors that determine the postprandial experience are poorly understood, despite their potential role in personalized diets and healthy eating habits. Current data suggest that the characteristics of the meal (amount, palatability, composition), the activity of the digestive system (suited processing), and the receptivity of the eater (influenced by multiple conditioning factors) may be important in this context.

The momentary interplay of affect, attention bias, and expectancies as predictors of binge eating in the natural environment

OBJECTIVE

Affect regulation, eating expectancies, and attention toward food-related cues are interrelated constructs that have been implicated in the maintenance of binge eating. While these processes show considerable temporal variability, the momentary associations between these domains have not been elucidated. This study examined a model that posited momentary fluctuations in affect, eating expectancies, and attention bias (AB) would interact to predict subsequent binge eating.

METHOD

Forty women who endorsed recurrent binge eating completed a 10-day ecological momentary assessment protocol with ambulatory measures of AB (i.e., dot-probe task with palatable food and neutral cues) and self-report assessments of positive and negative affect, eating expectancies (i.e., the belief that eating would improve one's mood), and binge-eating symptoms.

RESULTS

Generalized linear mixed models indicated higher momentary AB toward palatable food was associated with increased risk of subsequent binge eating, and a two-way interaction showed that moments of higher eating expectancies and negative affect were associated with increased likelihood of subsequent binge eating. Also, a three-way interaction emerged, in that the association between eating expectancies and subsequent binge eating was strongest at lower levels of positive affect and higher AB.

DISCUSSION

Together, findings partially supported hypotheses and demonstrate meaningful within-person fluctuations in AB that precede binge eating. Further, results demonstrate that the momentary influence of eating expectancies on binge eating depends on both affective state and attentional processes.

An event-related potential study of consumers' responses to food bundles

We conducted two event-related potentials (ERP) experiments to investigate consumers' responses to different types of food bundles. In Experiment 1, the participants were instructed to indicate their wanting of a three-yogurt bundle when their neural activity was recorded. The results of self-report wanting scores revealed that the participants wanted bundles consisting of their favorite yogurt products more than those of disliked products. Such a difference in self-report scores was also indexed by the N2 in frontal brain and the P1 in the left hemisphere. By contrast, bundles consisting of three different yogurt products elicited a smaller amplitude of the N2 than bundles consisting of two favorite products and one disliked product, but these two types of bundles received comparable wanting scores. Moreover, we asked the participants in Experiment 2 to perform a visual discrimination task on these bundles, and did not found these effects on the N2 or the P1. Collectively, these results revealed neural activities underlying consumers' responses to food rewards, and demonstrated the role of individuals' variety-seeking tendency in wanting process.

Shared striatal activity in decisions to satisfy curiosity and hunger at the risk of electric shocks

Curiosity is often portrayed as a desirable feature of human faculty. However, curiosity may come at a cost that sometimes puts people in harmful situations. Here, using a set of behavioural and neuroimaging experiments with stimuli that strongly trigger curiosity (for example, magic tricks), we examine the psychological and neural mechanisms underlying the motivational effect of curiosity. We consistently demonstrate that across different samples, people are indeed willing to gamble, subjecting themselves to electric shocks to satisfy their curiosity for trivial knowledge that carries no apparent instrumental value. Also, this influence of curiosity shares common neural mechanisms with that of hunger for food. In particular, we show that acceptance (compared to rejection) of curiosity-driven or incentive-driven gambles is accompanied by enhanced activity in the ventral striatum when curiosity or hunger was elicited, which extends into the dorsal striatum when participants made a decision.

Liking and Acceptability of Whole Grains Increases with a 6-Week Exposure but Preferences for Foods Varying in Taste and Fat Content Are Not Altered: A Randomized Controlled Trial

BACKGROUND

Since 2005, the Dietary Guidelines for Americans have recommended consuming at least half of total grains as whole grains (WGs) for optimal health benefits; however, consumption of WGs falls far short of recommended amounts.

OBJECTIVE

This study aimed to evaluate the effect of mere exposure to WGs on liking, acceptability, and consumption of WG foods and to determine if exposure to WG would influence liking and wanting for other foods varying in fat content and sweet taste.

METHODS

Healthy, self-identified low WG consumers (n = 45) were randomly assigned to either a 6-wk WG intervention or a refined grain (RG) control condition during which they received a weekly market basket of grain products to incorporate into daily meals and snacks. Consumption of grain products was measured by weekly logs and weigh-backs. A sensory evaluation protocol was conducted at baseline and week 6 to evaluate changes in perception of grain products. Computer tasks designed to measure liking and wanting for other foods varying in high/low-fat content and sweet/savory taste were also completed at baseline and week 6.

RESULTS

Participants in the WG group significantly increased WG consumption. Exposure to WG products resulted in improved ratings of liking, flavor, texture, and willingness to include WG in the regular diet. No significant changes in liking or wanting for foods representing high-fat sweet (HFSW), low-fat sweet (LFSW), high-fat savory (HFSA), or low-fat savory (LFSA) categories were found in the WG group. In contrast, exposure to RG foods resulted in an increased explicit wanting for HFSW and LFSW and a decreased wanting for HFSA foods.

CONCLUSIONS

Mere exposure to WG foods represents a feasible and easily applied behavioral strategy for increasing consumption of WGs. Encouraging consumers to focus on enjoyment of the taste may be more effective than emphasizing the health benefits of WG consumption. This trial was registered at clinicaltrials.gov as NCT01403857.

Neural response to fast food commercials in adolescents predicts intake

BACKGROUND

Food advertising is a major contributor to obesity, and fast food (FF) restaurants are top advertisers. Research on the impact of food advertising in adolescents is lacking and no prior research has investigated neural predictors of food intake in adolescents. Neural systems implicated in reward could be key to understanding how food advertising drives food intake.

OBJECTIVES

To investigate how neural responses to both unhealthy and healthier FF commercials predict food intake in adolescents.

METHODS

A cross-sectional sample of 171 adolescents (aged 13-16 y) who ranged from normal weight to obese completed an fMRI paradigm where they viewed unhealthy and healthier FF and nonfood commercials. Adolescents then consumed a meal in a simulated FF restaurant where foods of varying nutritional profiles (unhealthy compared with healthier) were available.

RESULTS

Greater neural activation in reward-related regions (nucleus accumbens, r = 0.29; caudate nucleus, r = 0.27) to unhealthy FF commercials predicted greater total food intake. Greater responses to healthier FF relative to nonfood commercials in regions associated with reward (i.e., nucleus accumbens, r = 0.24), memory (i.e., hippocampus, r = 0.32), and sensorimotor processes (i.e., anterior cerebellum, r = 0.33) predicted greater total food and unhealthier food intake, but not healthier food intake. Lower activation in neural regions associated with visual attention and salience (e.g., precuneus, r = -0.35) to unhealthy relative to healthier FF commercials predicted healthier food intake.

CONCLUSIONS

These findings suggest that FF commercials contribute to overeating in adolescents through reward mechanisms. The addition of healthier commercials from FF restaurants is unlikely to encourage healthier food intake, but interventions that reduce the ability of unhealthy FF commercials to capture attention could be beneficial. However, an overall reduction in the amount of FF commercials exposure for adolescents is likely to be the most effective approach.

Food Reward and Food Choice. An Inquiry Through The Liking and Wanting Model

What if consumers are getting obese because eating less calories is more difficult for persons that have a higher pleasure and desire towards food (Ikeda et al., 2005) and food companies do not help given only a two extreme option choice to satisfy their needs (i.e., low calories vs. high calories or healthy vs. unhealthy)? Reward systems are being described with a new conceptual approach where liking—the pleasure derived from eating a given food—and wanting—motivational value, desire, or craving—can be seen as the significant forces guiding eating behavior. Our work shows that pleasure (liking), desire (wanting), and the interaction between them influence and are good predictors of food choice and food intake. Reward responses to food are closely linked to food choice, inducing to caloric overconsumption. Based on the responses given to a self-administered questionnaire measuring liking and wanting attitudes, we found three different segments named ‘Reward lovers,’ ‘Half epicurious,’ and ‘Non indulgents’. Their behavior when choosing food is quite different. Results show differential effects on caloric consumption depending on segments. The introduction of more food choices that try to balance their content is a win-win strategy for consumers, companies, and society.

On the Nature of the Mother-Infant Tie and Its Interaction With Freudian Drives

The affective bond between an infant and its caregiver, the so-called mother-infant tie, was analyzed by various reputable psychologists (e.g., Ainsworth, Clark, Erikson, Anna Freud, Harlow, Klein, Spitz, and Winnicott) but both the basic tenets of the bond and the importance of the trauma of maternal deprivation for personality disorders in adults were introduced by Bowlby. Although Bowlby was a trained psychoanalyst, he rejected central cornerstones of Freudian theory (esp. drive theory) and used concepts promulgated by renowned ethologists (Tinbergen and Lorenz) to establish his framework of "instinctive behavior" that has been developed further into the concept of "attachment theory" under the influence of Mary Ainsworth. However, since any precise experimental facts were lacking when Bowlby formulated his ideas on the concept of instinctive behavior, the whole framework is a descriptive, category-driven approach (like the ones of Freudian drives). In order to connect the mother-infant tie - as propounded by Bowlby - with experimental data, this manuscript undertakes a biochemical analysis of it because this strategy proved somewhat successful in relation to Freudian drives. The analysis unfolded that the neurochemical oxytocin, released by the action of sensory nerves, is of utmost importance for the operation of the mother-infant tie. Furthermore, multiple evidences have been presented to the fact that there is strong interaction between unconsciously operating Freudian drives and the consciously acting mother-infant tie (that is now classified as a drive). The outlined interaction in conjunction with the classification of attachment urges as drives gave a very detailed insight into how a SEEKING-derived reward can be evoked during operation of the mother-infant tie. In summary, there is no need to marginalize either the mother-infant tie or Freudian drives but rather there is need to respect both (principally different) impulses in moving toward a more extensive description.

Obesity Therapy: How and Why?

Background:

Obesity represents the second preventable mortality cause worldwide, and is very often associated with type 2 Diabetes Mellitus (T2DM). The first line treatment is lifestyle modification to weight-loss, but for those who fail to achieve the goal or have difficulty in maintaining achieved results, pharmacological treatment is needed. Few drugs are available today, because of their side effects.

Objective:

We aim to review actual pharmacological management of obese patients, highlighting differences between Food and Drug Administration - and European Medicine Agency-approved molecules, and pointing out self-medications readily obtainable and widely distributed.

Methods:

Papers on obesity, weight loss, pharmacotherapy, self- medication and diet-aid products were selected using Medline. Research articles, systematic reviews, clinical trials and meta-analyses were screened.

Results:

Anti-obesity drugs with central mechanisms, such as phentermine and lorcaserin, are available in USA, but not in Europe. Phentermine/topiramate and naltrexone/bupropion combinations are now available, even though the former is still under investigation from EMA. Orlistat, with peripheral mechanisms, represents the only drug approved for weight reduction in adolescents. Liraglutide has been approved at higher dose for obesity. Anti-obesity drugs, readily obtainable from the internet, include crude-drug products and supplements for which there is often a lack of compliance to national regulatory standards.

Conclusion:

Mechanisms of weight loss drugs include the reduction of energy intake or the increase in energy expenditure and sense of satiety as well as the decrease of hunger or the reduction in calories absorption. Few drugs are approved, and differences exist between USA and Europe. Moreover, herbal medicines and supplements often sold on the internet and widely used by obese patients, present a risk of adverse effects.

Food-Related Attentional Bias in Individuals with Normal Weight and Overweight: A Study with a Flicker Task

The primary purpose of the present study was to investigate attentional biases for food-related stimuli in individuals with overweight and normal weight using a flicker paradigm. Specifically, it was tested whether attention allocation processes differ between individuals with overweight and normal weight using transient changes of food-related and neutral pictures. Change detection latencies in objects of central interest (CI) or objects of marginal interest (MI) were measured as an index of attention allocation in a sample of fifty-three students with overweight/obesity and sixty students with normal weight during a flicker paradigm with neutral, hypercaloric and hypocaloric food pictures. Both groups of participants showed an attentional bias for food-related pictures as compared to neutral pictures. However, the bias was larger in individuals with overweight than in individuals with normal weight when changes were of marginal interest, suggesting a stronger avoidance of the food-related picture. This study showed that food-related stimuli influence attention allocation processes in both participants with overweight and normal weight. In particular, as compared to individuals with normal weight, those with overweight seem to be characterised by a stronger attentional avoidance of (or smaller attention maintenance on) food-related stimuli that could be considered as a voluntary strategy to resist food consumption.

Differential rearing alters taste reactivity to ethanol, sucrose, and quinine

RATIONALE

Early-life environment influences reinforcer and drug motivation in adulthood; however, the impact on specific components of motivation, including hedonic value ("liking"), remains unknown.

OBJECTIVES

The current study determined whether differential rearing alters liking and aversive responding to ethanol, sucrose, and quinine in an ethanol-naïve rat model.

METHODS

Male and female rats were reared for 30 days starting at postnatal day 21 in either an enriched (EC), isolated (IC), or standard condition (SC). Thereafter, all rats had indwelling intraoral fistulae implanted and their taste reactivity to water, ethanol (5, 10, 20, 30, 40% v/v), sucrose (0.1, 0.25, 0.5 M), and quinine (0.1, 0.5 mM) was recorded and analyzed.

RESULTS

EC rats had higher amounts of liking responses to ethanol, sucrose, and quinine and higher amounts of aversive responses to ethanol and quinine compared to IC rats. While EC and IC rats' responses were different from each other, they both tended to be similar to SCs, who fell in between the EC and IC groups.

CONCLUSIONS

These results suggest that environmental enrichment may enhance sensitivity to a variety of tastants, thereby enhancing liking, while isolation may dull sensitivity, thereby dulling liking. Altogether, the evidence suggests that isolated rats have a shift in the allostatic set-point which may, in part, drive increased responding for a variety of rewards including ethanol and sucrose. Enriched rats have enhanced liking of both sucrose and ethanol suggesting that enrichment may offer a unique phenotype with divergent preferences for incentive motivation.

A developmental framework of binge-eating disorder based on pediatric loss of control eating

Although binge-eating disorder may manifest in childhood, a significantly larger proportion of youth report episodes involving a loss of control while eating, the hallmark feature of binge eating that predicts excess weight gain and obesity. Adults with binge-eating disorder often report that symptoms emerged during childhood or adolescence, suggesting that a developmental perspective of binge eating may be warranted. Thus, loss of control eating may be a marker of prodromal binge-eating disorder among certain susceptible youth. The present article offers a broad developmental framework of binge-eating disorder and proposes areas of future research to determine which youths with loss of control eating are at risk for persistent and exacerbated behavior that may develop into binge-eating disorder and adult obesity. To this end, this article provides an overview of loss of control eating in childhood and adolescence, including its characterization, etiology, and clinical significance, with a particular focus on associations with metabolic risk, weight gain, and obesity. A conceptual model is proposed to further elucidate the mechanisms that may play a role in determining which youths with loss of control are at greatest risk for binge-eating disorder and obesity. Ways in which treatments for adult binge-eating disorder may inform approaches to reduce loss of control eating and prevent excess weight gain in youth are discussed. (PsycINFO Database Record (c) 2020 APA, all rights reserved).