The role of palatable food and hunger as trigger factors in an animal model of stress induced binge eating

Evaluating dietary restriction as a maintaining factor in binge-eating disorder

OBJECTIVE

Prominent theories of binge-eating (BE) maintenance highlight dietary restriction as a key precipitant of BE episodes. Consequently, treatment approaches for eating disorders (including binge-eating disorder; BED) seek to reduce dietary restriction in order to improve BE symptoms. The present study tested the hypothesis that dietary restriction promotes BE among 112 individuals with BED.

METHODS

Participants completed a 7-day ecological momentary assessment (EMA) protocol before and after completing 17 weeks of either Integrative Cognitive-Affective Therapy or guided self-help cognitive behavioral therapy. Analyses examined whether dietary restriction on 1 day of the baseline EMA protocol predicted risk for BE later that same day, and on the following day. Changes in dietary restriction over the course of treatment were also evaluated as a predictor of change in BE from pre-treatment to post-treatment. Baseline dietary restraint was examined as a moderator of the above associations.

RESULTS

Dietary restriction did not predict BE later the same day, and changes in restriction were not related to changes in BE across treatment, regardless of baseline dietary restraint levels. Restriction on 1 day did predict increased BE risk on the following day for individuals with higher levels of dietary restraint, but not those with lower levels.

DISCUSSION

These findings challenge the assumption that dietary restriction maintains BE among all individuals with BED. Rather, results suggest that dietary restriction may be largely unrelated to BE maintenance in this population, and that reducing dietary restriction generally does not have the intended effect on BE frequency.

Eating disorders and obesity: bridging clinical, neurobiological, and therapeutic perspectives

Eating disorders (EDs) and obesity are complex health conditions sharing various risk and maintenance factors, intensified in cases of comorbidity. This review explores the similarities and connections between these conditions, examining different facets from a multidisciplinary perspective, among them comorbidities, metabolic and psychological factors, neurobiological aspects, and management and therapy implications. We aim to investigate the common characteristics and complexities of weight and EDs and explore their interrelationships in individuals who experience both. The rising prevalence of EDs in people with obesity necessitates integrated approaches to study this comorbidity and to identify and analyze both common and distinct features of these conditions. This review may offer new opportunities for simultaneous prevention and management approaches, as well as future lines of research.

Motives and food craving: Associations with frequency of hyper-palatable food intake among college students

BACKGROUND

College food environments provide wide access to hyper-palatable foods (HPF). Palatable eating motives and craving are individual factors that may impact HPF intake. Nevertheless, no study to date has examined the relationship between these factors and frequency of HPF intake in a dormitory all-you-can-eat-style cafeteria meal, a typical college food setting.

METHODS

College students (N = 218) self-reported frequency of HPF intake at a college cafeteria meal and their frequency of HPF intake in the overall diet. Quasipoisson and logistic regression models tested whether palatable eating motives (assessed via the Palatable Eating Motives Scale) and craving (assessed via the Food Craving Inventory) were associated with the rate of HPF intake during the cafeteria meal and excess frequency of HPF intake in the overall diet.

RESULTS

Craving was associated with a 19% higher rate of HPF intake during the cafeteria meal (RR = 1.19; p = .015) and a >2-fold higher likelihood of excess frequency of HPF intake the overall diet (OR = 2.69; p < .001). Coping motive was associated with an 87% higher likelihood of excess frequency of HPF intake in the overall diet (OR = 1.87; p = .002), but not in the cafeteria meal. Reward enhancement, social and conformity motives were not significantly associated with the frequency of HPF intake in either setting.

CONCLUSIONS

Results highlight the role of craving and coping motive in the frequency of HPF intake among college students. Prevention efforts may consider targeting craving and eating to cope to potentially address frequency of HPF intake among college students.

Microbiota-gut-brain axis drives overeating disorders

Overeating disorders (ODs), usually stemming from dieting history and stress, remain a pervasive issue in contemporary society, with the pathological mechanisms largely unresolved. Here, we show that alterations in intestinal microbiota are responsible for the excessive intake of palatable foods in OD mice and patients with bulimia nervosa (BN). Stress combined with a history of dieting causes significant changes in the microbiota and the intestinal metabolism, which disinhibit the vagus nerve terminals in the gut and thereby lead to a subsequent hyperactivation of the gut-brain axis passing through the vagus, the solitary tract nucleus, and the paraventricular nucleus of the thalamus. The transplantation of a probiotic Faecalibacterium prausnitzii or dietary supplement of key metabolites restores the activity of the gut-to-brain pathway and thereby alleviates the OD symptoms. Thus, our study delineates how the microbiota-gut-brain axis mediates energy balance, unveils the underlying pathogenesis of the OD, and provides potential therapeutic strategies.

Linking drug and food addiction: an overview of the shared neural circuits and behavioral phenotype

Despite a lack of agreement on its definition and inclusion as a specific diagnosable disturbance, the food addiction construct is supported by several neurobiological and behavioral clinical and preclinical findings. Recognizing food addiction is critical to understanding how and why it manifests. In this overview, we focused on those as follows: 1. the hyperpalatable food effects in food addiction development; 2. specific brain regions involved in both food and drug addiction; and 3. animal models highlighting commonalities between substance use disorders and food addiction. Although results collected through animal studies emerged from protocols differing in several ways, they clearly highlight commonalities in behavioral manifestations and neurobiological alterations between substance use disorders and food addiction characteristics. To develop improved food addiction models, this heterogeneity should be acknowledged and embraced so that research can systematically investigate the role of specific variables in the development of the different behavioral features of addiction-like behavior in preclinical models.

Characterizing naturalistic meal timing, energy intake, and macronutrient intake among individuals with loss of control eating

Binge eating demonstrates an evening diurnal shift among individuals with eating disorders. Disruptions to diurnal appetitive rhythms may be somewhat chronic and set the stage for additional disruptions to prompt binge eating. Despite known diurnal shifts in binge eating and related constructs (e.g., mood) and detailed characterizations of binge-eating episodes, no findings to date describe the naturalistic diurnal timing and composition of energy and nutrient intake on days with and without loss of control eating. We aimed to characterize eating behaviors (i.e., meal timing, energy intake, and macronutrient composition) across seven days in individuals with binge-spectrum eating disorders, assessing differences between eating episodes and days with and without loss of control eating. Undergraduate students (N = 51; 76.5% female) who endorsed past 28-day loss of control eating completed a 7-day naturalistic ecological momentary assessment protocol. Participants completed daily food diaries and reported instances of loss of control eating across the 7-day period. Results indicated that episodes of loss of control were more likely to occur later in the day, but overall meal timing did not differ across days with and without loss of control. Similarly, greater caloric consumption was more likely for episodes with loss of control, but overall caloric consumption did not differ between days with and without loss of control. Analysis of nutritional content demonstrated differences between both episodes and days with and without loss of control for carbohydrates and total fats, but not for protein. Findings provide support for the hypothesized role disruptions in diurnal appetitive rhythms play in maintaining binge eating via consistent irregularities, underscoring the importance of examining treatment adjuncts that intervene on the regulation of meal timing to enhance eating disorder treatment outcomes.

A Framework for Developing Translationally Relevant Animal Models of Stress-Induced Changes in Eating Behavior

Stress often affects eating behaviors, leading to increased eating in some individuals and decreased eating in others. Identifying physiological and psychological factors that determine the direction of eating responses to stress has been a major goal of epidemiological and clinical studies. However, challenges of standardizing the stress exposure in humans hinder efforts to uncover the underlying mechanisms. The issue of what determines the direction of stress-induced feeding responses has not been directly addressed in animal models, but assays that combine stress with a feeding-related task are commonly used as readouts of other behaviors, such as anxiety. Sex, estrous cyclicity, circadian cyclicity, caloric restriction, palatable diets, elevated body weight, and properties of the stressors similarly influence feeding behavior in humans and rodent models. Yet, most rodent studies do not use conditions that are most relevant for studying feeding behavior in humans. This review proposes a conceptual framework for incorporating these influences to develop reproducible and translationally relevant assays to study effects of stress on food intake. Such paradigms have the potential to uncover links between emotional eating and obesity as well as to the etiology of eating disorders.

Hunger mediates the relationship between food insecurity and binge eating among bariatric surgery candidates

BACKGROUND

The food insecurity-obesity paradox suggests that people lacking access to adequately nutritious foods are more susceptible to disordered eating. However, the mechanisms underlying the relationship between food insecurity and binge eating are not well understood.

OBJECTIVES

This study sought to assess the role of eating behaviors (i.e., cognitive restraint, disinhibition, and hunger) as mediators between food insecurity and binge eating among a sample of preoperative bariatric candidates.

SETTING

University hospital in the Appalachian region of the United States.

METHODS

A total of 369 adults seeking bariatric surgery were included in this cross-sectional study. Patients completed validated measures of food insecurity and eating behaviors as part of a routine psychological evaluation prior to bariatric surgery.

RESULTS

Food insecurity was significantly related to binge eating symptoms (r[369] = .14, P < .01) and hunger (r[369] = .11, P < .05). Hunger mediated the relationship between food insecurity and binge eating (b = 1.23, standard error = .62, 95% confidence interval .08-2.54). Food insecurity was not associated with restraint (r[369] = .06, P = .27) or disinhibition (r[369] = .02, P = .69).

CONCLUSIONS

Food insecurity presents a unique pathway to binge eating that has several implications for intervention prior to bariatric surgery. Identification of food insecurity and the subsequent effects on eating behaviors is crucial to understanding the factors relevant to disordered eating prior to bariatric surgery.

Deciphering the molecular mechanism of water boiling at heterogeneous interfaces

Water boiling control evolution of natural geothermal systems is widely exploited in industrial processes due to the unique non-linear thermophysical behavior. Even though the properties of water both in the liquid and gas state have been extensively studied experimentally and by numerical simulations, there is still a fundamental knowledge gap in understanding the mechanism of the heterogeneous nucleate boiling controlling evaporation and condensation. In this study, the molecular mechanism of bubble nucleation at the hydrophilic and hydrophobic solid-water interface was determined by performing unbiased molecular dynamics simulations using the transition path sampling scheme. Analyzing the liquid to vapor transition path, the initiation of small void cavities (vapor bubbles nuclei) and their subsequent merging mechanism, leading to successively growing vacuum domains (vapor phase), has been elucidated. The molecular mechanism and the boiling nucleation sites' location are strongly dependent on the solid surface hydrophobicity and hydrophilicity. Then simulations reveal the impact of the surface functionality on the adsorbed thin water molecules film structuring and the location of high probability nucleation sites. Our findings provide molecular-scale insights into the computational aided design of new novel materials for more efficient heat removal and rationalizing the damage mechanisms.

Weight Stigmatization and Binge Eating in Asian Americans with Overweight and Obesity

Weight stigma and binge eating have been found to be associated in Western populations; however, this relationship is understudied among Asian Americans. The aims of the study were to (1) investigate the prevalence of binge eating and its relationship with experienced weight stigma in higher-weight Asian Americans, and (2) examine whether the level of acculturation moderates this relationship. Data were collected from a cross-sectional study with 166 higher-weight Asian American adults living in North Carolina, United States. Demographic data, the frequency of experiencing weight stigma, the severity of binge eating, the levels of acculturation, the perceived racism against Asians, and perceived stress were assessed via self-reported questionnaires. The results indicated that experienced weight stigma was a significant independent predictor over and above the effects of other stressors, such as racism and general stress. The level of acculturation did not influence the relationship between the experienced weight stigma and binge eating after adjusting for relevant covariates. Our findings contribute to the limited literature examining weight stigma and binge eating among Asian American populations, highlighting that higher levels of experienced weight stigma are associated with a greater degree of binge eating.

Can Participants' Characteristics Predict Benefit from a Multimodal Burnout Prevention Program? Secondary Analysis of a Randomized Controlled Trial Conducted in Germany

Chronic psychological distress appears to be increasing markedly among the working population. A recent randomized controlled trial (RCT) supported the effectiveness of a three-week outpatient burnout prevention program-comprised of stress management interventions, relaxation, physical exercise, and moor baths followed by massage-in reducing perceived stress and emotional exhaustion. However, the effectiveness of treatments in the real world that were shown to be efficacious in RCTs is related to the appropriate selection of individuals who are most likely to yield sustainable gains. Therefore, factors predicting the intensity of response and nonresponse of individuals to treatment are of interest. This secondary data analysis aims to explore predictors of response to the outpatient burnout prevention program in a sample of eighty employed persons at high risk of burnout. Hierarchical linear regression was performed to identify predictors of successful response-defined by lower perceived stress at last follow up. Nutritional behavior, symptoms of eating disorder syndrome, and well-being were significant predictors of perceived stress at last follow up, when adjusted for age, sex, education level, baseline stress values, and timing of intervention. Persons with low levels of well-being, poor nutritional behavior, and higher symptoms of eating disorders should be given special care and attention to ensure that they respond well to the outpatient burnout prevention program.

Food-Cal: development of a controlled database of high and low calorie food matched with non-food pictures

BACKGROUND

Industrialization has led to more varied and attractive high-calorie foods. Health problems such as obesity and diabetes are partially attributed to eating-related self-regulation difficulties that may be caused by increasingly frequent cues for highly palatable foods. Research studies aim at understanding the factors underlying responses to food cues. This has led to the development of food stimuli databases. However, they present some limitations.

OBJECTIVES

This study aimed at providing a controlled set of pictures, including 40 food pictures with high- and low-calorie stimuli, matched with 40 non-food pictures. The second objective was to provide a ready-to-use database with normative data regarding responses and associations between demographic, anthropometric and eating-related characteristics, and picture ratings.

PARTICIPANTS

A sample of 264 participants rated the total set of pictures.

MEASURES

Attractiveness, arousal and palatability were assessed for each picture, as well as participant's current type of diet, BMI, hunger levels and eating behaviors (uncontrolled and emotional eating).

RESULTS

Image characteristics (shape, colors, luminance) were comparable between food and matched non-food pictures. Positive correlations were found between hunger levels and attractiveness, arousal and palatability of food. Uncontrolled and emotional eating was positively correlated with high-calorie food palatability, and uncontrolled eating was positively correlated with high-calorie food attractiveness. Participants who did not report any specific diet rated high-calorie foods as more attractive and arousing, whereas vegan and vegetarian participants assessed low-calorie foods as more attractive and palatable.

CONCLUSION

The Food-Cal controlled set of picture database can be considered as a useful tool for experimental research.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

Eating Disorders: An Evolutionary Psychoneuroimmunological Approach

Eating disorders are evolutionarily novel conditions. They lead to some of the highest mortality rates of all psychiatric disorders. Several evolutionary hypotheses have been proposed for eating disorders, but only the intrasexual competition hypothesis is extensively supported by evidence. We present the mismatch hypothesis as a necessary extension to the current theoretical framework of eating disorders. This hypothesis explains the evolutionarily novel adaptive metaproblem that has arisen when mating motives conflict with the large-scale and easy availability of hyper-rewarding but obesogenic foods. This situation is exacerbated particularly in those contemporary environments that are characterized by sedentary lifestyles, ever-present junk foods, caloric surplus and the ubiquity of social comparisons that take place via social media. Our psychoneuroimmunological model connects ultimate-level causation with proximate mechanisms by showing how the adaptive metaproblem between mating motives and food rewards leads to chronic stress and, further, to disordered eating. Chronic stress causes neuroinflammation, which increases susceptibility to OCD-like behaviors that typically co-occur with eating disorders. Chronic stress upregulates the serotonergic system and causes dysphoric mood in anorexia nervosa patients. Dieting, however, reduces serotonin levels and dysphoric mood, leading to a vicious serotonergic-homeostatic stress/starvation cycle whereby cortisol and neuroinflammation increase through stringent dieting. Our psychoneuroimmunological model indicates that between-individual and within-individual variation in eating disorders partially arises from (co)variation in gut microbiota and stress responsivity, which influence neuroinflammation and the serotonergic system. We review the advances that have been made in recent years in understanding how to best treat eating disorders, outlining directions for future clinical research. Current evidence indicates that eating disorder treatments should aim to reduce the chronic stress, neuroinflammation, stress responsivity and gut dysbiosis that fuel the disorders. Connecting ultimate causes with proximate mechanisms and treating biopsychosocial causes rather than manifest symptoms is expected to bring more effective and sophisticated long-term interventions for the millions of people who suffer from eating disorders.

Stress as a potential moderator of ovarian hormone influences on binge eating in women

Previous research has demonstrated significant associations between increased levels of ovarian hormones and increased rates of binge eating (BE) in women. However, whereas all women experience fluctuations in ovarian hormones across the menstrual cycle, not all women binge eat in response to these fluctuations, suggesting that other factors must contribute. Stress is one potential contributing factor. Specifically, it may be that hormone-BE associations are stronger in women who experience high levels of stress, particularly as stress has been shown to be a precipitant to BE episodes in women. To date, no studies have directly examined stress as a moderator of hormone-BE associations, but indirect data (that is, associations between BE and stress and between ovarian hormones and stress) could provide initial clues about moderating effects. Given the above, the purpose of this narrative review was to evaluate these indirect data and their promise for understanding the role of stress in hormone-BE associations. Studies examining associations between all three phenotypes (that is, ovarian hormones, stress, and BE) in animals and humans were reviewed to provide the most thorough and up-to-date review of the literature on the potential moderating effects of stress on ovarian hormone-BE associations. Overall, current evidence suggests that associations between hormones and BE may be stronger in women with high stress levels, possibly via altered hypothalamic-pituitary-adrenal axis response to stress and increased sensitivity to and altered effects of ovarian hormones during stress. Additional studies are necessary to directly examine stress as a moderator of ovarian hormone-BE associations and identify the mechanisms underlying these effects.

Animal Models of Eating Disorders

Eating disorders (EDs) include a range of chronic and disabling pathologies characterized by persistent maladaptive eating habits and/or behaviors aimed at controlling body shape and size, with important consequences on physical health. Different animal models of EDs have been developed to investigate pharmacological, environmental, and genetic determinants that contribute to the development and maintenance of these disorders as well as for the identification of potential therapeutic targets. In this chapter, we will provide an overview of the most useful animal models of EDs, focusing mainly on those used to study anorexia nervosa and binge eating disorder.

Shared Concerns and Opportunity for Joint Action in Creating a Food Environment That Supports Health

The food industry is a for-profit industry with high relevance to universal eating disorders prevention. To date, policy which targets the food industry and food environment has been underutilized in efforts to decrease the incidence of eating disorders and associated risk factors. In contrast, food policy has been extensively leveraged with the aim of reducing the incidence of obesity. While philosophical misalignments with these later efforts may have constituted an obstacle to identifying the food environment as a key target for eating disorders prevention, food policy is an area where shared interests can be found. Specifically, a shared goal of obesity and eating disorders prevention efforts is creating a food environment that supports health, while minimizing the influence of the food industry that profits from the sale of highly palatable, processed foods and “diet” foods and from increasing portions of foods served and eaten.

Research for leveraging food policy in universal eating disorder prevention

Policy and legislation have emerged as important levers for universal prevention efforts in the context of eating disorders. However, to date, little attention has been paid to generating research that will inform opportunities to regulate the food environment, specifically the way that food is produced and marketed. The present paper aims to lay out a framework for research that will examine (1) the ways in which food industry may influence risk for eating disorders and (2) the impact of legislative efforts on eating disorder cognitions and behaviors. For these two pathways, specific examples of research that would serve to inform policy efforts aiming to decrease the risk for eating disorders by targeting the food environment are proposed. Overall, the present paper aims to issue a call for the eating disorder field to become involved in food policy and regulation.

Diet matters: Glucocorticoid-related neuroadaptations associated with calorie intake in female rhesus monkeys

Exposure to psychosocial stressors increases consumption of palatable, calorically dense diets (CDD) and the risk for obesity, especially in females. While consumption of an obesogenic diet and chronic stress have both been shown to decrease dopamine 2 receptor (D2R) binding and alter functional connectivity (FC) within the prefrontal cortex (PFC) and the nucleus accumbens (NAcc), it remains uncertain how social experience and dietary environment interact to affect reward pathways critical for the regulation of motivated behavior. Using positron emission tomography (PET) and resting state functional connectivity magnetic resonance neuroimaging (rs-fMRI), in female rhesus monkeys maintained in a low calorie chow (n = 18) or a dietary choice condition (chow and a CDD; n = 16) for 12 months, the current study tested the overarching hypothesis that the adverse social experience resulting from subordinate social status would interact with consumption of an obesogenic diet to increase caloric intake that would be predicted by greater cortisol, lower prefrontal D2R binding potential (D2R-BP) and lower PFC-NAcc FC. Results showed that the consequences of adverse social experience imposed by chronic social subordination vary significantly depending on the dietary environment and are associated with alterations in prefrontal D2R-BP and FC in NAcc-PFC sub-regions that predict differences in caloric intake, body weight gain, and fat accumulation. Higher levels of cortisol in the chow-only condition were associated with mild inappetence, as well as increased orbitofrontal (OFC) D2R-BP and greater FC between the NAcc and the dorsolateral PFC (dlPFC) and ventromedial PFC (vmPFC). However, increased cortisol release in females in the dietary choice condition was associated with reduced prefrontal D2R-BP, and opposite FC between the NAcc and the vmPFC and dlPFC observed in the chow-only females. Importantly, the degree of these glucocorticoid-related neuroadaptations predicted significantly more total calorie intake as well as more consumption of the CDD for females having a dietary choice, but had no relation to calorie intake in the chow-only condition. Overall, the current findings suggest that dietary environment modifies the consequences of adverse social experience on reward pathways and appetite regulation and, in an obesogenic dietary environment, may reflect impaired cognitive control of food intake.

Independent and interactive associations of negative affect, restraint, and impulsivity in relation to binge eating among women

There is growing recognition that impulsivity may serve as an underlying risk factor for binge eating. In addition, the association of impulsivity with binge eating may be moderated by other affective and cognitive risk factors. This study examined independent and interactive associations of negative affect, dietary restraint, and facets of impulsivity with binge eating. A diverse sample of 566 undergraduate women completed online questionnaires of study variables. Results revealed a three-way interaction of negative affect, dietary restraint, and attentional impulsivity in relation to binge eating. Women who were high on each of these three variables reported the greatest levels of binge eating. In addition, a two-way interaction was found for negative affect and nonplanning impulsivity in relation to binge eating, such that nonplanning impulsivity strengthened the association between negative affect and binge eating. Attentional and nonplanning facets of impulsivity may function as an underlying trait-level risk factor interacts with affective and/or cognitive risk (e.g., negative affect, dietary restraint) factors to predict elevated binge eating.

The Association Between an Addictive Tendency Toward Food and Metabolic Characteristics in the General Newfoundland Population

Background: Our previous study of 29 obese food addiction (FA) patients found that FA is associated with lipid profiles and hormones which may be a factor in cardiovascular disease (CVD) and insulin resistance (IR). However, there is currently no data available regarding the relationship between FA symptoms and metabolic characteristics of CVD and IR in the general population. We designed this study to investigate the correlation between FA symptoms with lipid profiles and IR in men and women of the general Newfoundland population. Methods: 710 individuals (435 women and 275 men) recruited from the general Newfoundland population were used in analysis. FA symptoms were evaluated using the Yale Food Addiction Scale (YFAS). Glucose, insulin, HDL, LDL, total cholesterol and triglycerides levels were measured. IR was evaluated using the homeostatic model of assessment (HOMA). Participants were grouped by sex and menopausal status. Age, physical activity, calories and total % body fat were controlled. Results: Partial correlation analysis revealed that in men, YFAS symptom counts were significantly correlated with HOMA-β (r = 0.196, p = 0.021), triglycerides (r = 0.140, p = 0.025) and inversely correlated with HDL (r = -0.133, p = 0.033). After separating by menopausal status, pre-menopausal women exhibited no correlations and post-menopausal women had a significantcorrelation with triglycerides (r = 0.198, p = 0.016). Conclusion: FA is significantly correlated with several markers of metabolic disturbance in men and to a lesser extent, post-menopausal women, in the general population. Further research is required to explain sex specific associations and elucidate any potentially causal mechanisms behind this correlation.

A test of a state-based, self-control theory of binge eating in adults with obesity

It has been theorized that state the levels of self-control depletion (as caused by negative affect and restraint) may lead to binge eating (BE) when individuals also endorse momentary expectancies that eating will make them feel better (EE). Given commonalities in precipitants of BE across populations, the current study tested this theory in a sample of adults with obesity using ecological momentary assessment (EMA). Fifty obese adults completed the EMA protocol during which they provided pre-eating episode ratings of negative affect, restraint, and EE, and post-eating episode ratings of BE. Generalized estimating equations (GEE) identified a 3-way interaction between within-person pre-eating episode variables: higher self-control depletion (e.g., higher restraint and higher negative affect) was predictive of BE episodes only when individuals also endorsed higher EE. To our knowledge, this is the first empirical test of this theory, highlighting the impact of momentary self-control depletion and EE on BE in obese adults.

Foods are differentially associated with subjective effect report questions of abuse liability

OBJECTIVES

The current study investigates which foods may be most implicated in addictive-like eating by examining how nutritionally diverse foods relate to loss of control consumption and various subjective effect reports. Subjective effect reports assess the abuse liabilities of substances and may similarly provide insight into which foods may be reinforcing in a manner that triggers an addictive-like response for some individuals.

DESIGN

Cross-sectional.

SETTING

Online community.

PARTICIPANTS

507 participants (n = 501 used in analyses) recruited through Amazon MTurk.

MEASUREMENTS

Participants (n = 501) self-reported how likely they were to experience a loss of control over their consumption of 30 nutritionally diverse foods and rated each food on five subjective effect report questions that assess the abuse liability of substances (liking, pleasure, craving, averseness, intensity). Hierarchical cluster analytic techniques were used to examine how foods grouped together based on each question.

RESULTS

Highly processed foods, with added fats and/or refined carbohydrates, clustered together and were associated with greater loss of control, liking, pleasure, and craving. The clusters yielded from the subjective effect reports assessing liking, pleasure, and craving were most similar to clusters formed based on loss of control over consumption, whereas the clusters yielded from averseness and intensity did not meaningfully differentiate food items.

CONCLUSION

The present work applies methodology used to assess the abuse liability of substances to understand whether foods may vary in their potential to be associated with addictive-like consumption. Highly processed foods (e.g., pizza, chocolate) appear to be most related to an indicator of addictive-like eating (loss of control) and several subjective effect reports (liking, pleasure, craving). Thus, these foods may be particularly reinforcing and capable of triggering an addictive-like response in some individuals. Future research is warranted to understand whether highly processed foods are related to these indicators of abuse liability at a similar magnitude as addictive substances.

Arcuate nucleus homeostatic systems reflect blood leptin concentration but not feeding behaviour during scheduled feeding on a high-fat diet in mice

Hypothalamic homeostatic and forebrain reward-related genes were examined in the context of scheduled meal feeding without caloric restriction in C57BL/6 mice. Mice fed ad libitum but allowed access to a palatable high-fat (HF) diet for 2 hours a day rapidly adapted their feeding behaviour and consumed approximately 80% of their daily caloric intake during this 2-hour scheduled feed. Gene expression levels were examined during either the first or second hour of scheduled feeding vs 24 hours ad libitum feeding on the same HF diet. Gene expression of neuropeptide Y, agouti-related peptide, cocaine- and amphetamine-regulated transcript, pro-opiomelanocortin, long-form leptin receptor and suppressor of cytokine signalling-3 in the hypothalamic arcuate nucleus (ARC), as well as enkephalin, dynorphin, dopamine-2-receptor and dopamine-3-receptor in the nucleus accumbens (NAcc) in the forebrain, were measured by in situ hybridisation. Mice fed ad libitum on a HF diet had the highest total caloric intake, body weight gain, fat mass and serum leptin, whereas schedule-fed mice had a mild obese phenotype with intermediate total caloric intake, body weight gain, fat mass and serum leptin. The effects of feeding regime on ARC gene expression were emphasised by significant positive or negative correlations with body weight gain, fat mass and blood leptin, although they did not appear to be related to feeding behaviour in the schedule-fed groups (ie, the large, binge-type meals) and did not reveal any potential candidates for the regulation of these meals. Mechanisms underlying large meal/binge-type eating may be regulated by nonhomeostatic hedonic processes. However, assessment of opioid and dopamine receptor gene expression in the NAcc did not reveal evidence of involvement of these genes in regulating large meals. This complements our previous characterisation of ARC and NAcc genes in schedule-fed mice and rats, although it still leaves open the fundamental question about the underlying mechanisms of meal feeding.

Role of food preoccupation and current dieting in the associations of parental feeding practices to emotional eating in young adults: A moderated mediation study

Parental feeding practices reflecting coercive control are related to children's later eating behaviors, but the mechanisms underlying these effects remain poorly understood. This study examined the relationships between recalled childhood experiences of parental pressure to eat and restriction and current food preoccupation, dieting, and emotional eating in a racially diverse sample of college students (N = 711). Results revealed that parental restriction, but not pressure to eat, was associated with more emotional eating (r = 0.18, p < 0.0001). Food preoccupation mediated the association between restriction and emotional eating (95% CI [3.6495-7.2231]); however, a moderated mediation model revealed that the strength of the indirect effect of restrictive feeding on emotional eating through food preoccupation was significantly different for dieters and non-dieters (index of moderated mediation = 1.79, Boot SE = 0.79; 95% bias-corrected bootstrap CI [-3.5490 to -0.4515]). These findings provide unique insight into the mechanisms linking parental feeding practices with emotional eating in young adulthood. Future studies attempting to clarify the processes through which child feeding practices impact later eating behaviors should consider the role of current dieting.

Eating in the absence of hunger during childhood predicts self-reported binge eating in adolescence

OBJECTIVE

The objectives of the current study were to examine whether eating in the absence of hunger (EAH) at age 7 predicted reports of self-reported binge eating at age 15 and to identify factors among girls with high-EAH that moderated risk of later binge eating.

METHOD

Subjects included 158 girls assessed at age 7 and age 15. Logistic regression was used to predict binge eating at age 15 from calories consumed during EAH at age 7. A series of logistic regressions were used to examine the odds of reporting binge eating given levels of risk factors (e.g., anxiety) among those with high-EAH in childhood.

RESULTS

Girls' EAH intake predicted reports of binge eating at age 15; after adjusting for age 7 BMI, for each additional 100kcal consumed, girls were 1.7 times more likely to report binge eating in adolescence. Among those with high-EAH, BMI, anxiety, depression, dietary restraint, emotional disinhibition, and body dissatisfaction all predicted binge eating.

DISCUSSION

EAH during childhood predicted reports of binge eating during adolescence; girls with elevated BMI, negative affect, and maladaptive eating- and weight-related cognitions were at increased risk. High-EAH in childhood may be useful for indicating those at risk for developing binge eating.

Patterned feeding induces neuroendocrine, behavioral and genetic changes that promote palatable food intake

BACKGROUND

Selection of a healthy diet is the cornerstone for treating obesity and metabolic disease. Unfortunately, the majority of diets fail leading to weight regain and in some cases, pathological feeding behavior. We hypothesize that alternating bouts of caloric overconsumption and caloric restriction, behavioral manifestations of dieting induce neuroendocrine, behavioral and genetic changes that promote future bouts of palatable food intake.

METHODS

To test this hypothesis, we subjected male Long-Evans rats to a high-fat diet (HFD) feeding paradigm that induced a pattern of caloric overconsumption and caloric restriction. Under these conditions we measured operant responding for sucrose, pre-meal ghrelin secretion, the effects of peripheral ghrelin blockade on patterned feeding, HFD intake in an aversive environment and mRNA expression of the ghrelin receptor, orexin, orexin-1 and 2 receptors, and FTO in the medial prefrontal cortex, lateral hypothalamus and ventral tegmental area.

RESULTS

Rats subjected to this feeding regimen displayed increased ghrelin levels prior to HFD exposure and blockade of this response attenuated patterned feeding behavior. In addition, patterned feeding promoted enhanced motivation for sucrose, diminished extinction of this response and increased HFD intake in an aversive environment. The neuroendocrine and behavioral changes correlated with increased hypothalamic expression of the ghrelin receptor and FTO.

CONCLUSION

Collectively, these data indicate that patterns of feeding that include caloric overconsumption and caloric restriction induce neuroendocrine and neurobiological changes that signify an enhanced drive for palatable food.

A commentary on the "eating addiction" versus "food addiction" perspectives on addictive-like food consumption

The food addiction construct posits that vulnerable individuals may experience an addictive-like response to certain foods, such as those high in fat and refined carbohydrates. Recently, an alternative model to food addiction was proposed, suggesting that the act of eating may be a behavioral addiction that can trigger an addictive-like response in susceptible individuals. One major rationale for the eating addiction framework is that the assessment of food addiction is based on behavioral indicators, such as consuming greater quantities of food than intended and eating certain foods despite negative consequences. It is also suggested that the lack of investigation into which foods and food attributes (e.g., sugar) may have an addictive potential is evidence that food addiction does not parallel a substance-based addiction and more closely resembles a behavioral addiction. The present paper provides a commentary suggesting that the substance-based, food-addiction framework is more appropriate than the behavioral-addiction, eating-addiction perspective to conceptualize addictive-like food consumption. In order to illustrate this point, this manuscript will discuss behavioral components characteristic of all substance-use disorders, preliminary evidence to suggest that all foods are not equally associated with addictive-like eating, and key differences between the hypothesized eating addiction phenotype and the only existing behavioral addiction in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), gambling disorder. Further, this paper will consider implications of applying an addiction label to food versus eating and suggest future research directions to evaluate whether food addiction is a valid and clinically useful construct.

The relationship between high residential density in student dormitories and anxiety, binge eating and Internet addiction: a study of Chinese college students

Context

Although various studies have indicated that high residential density may affect health and psychological outcomes, to our knowledge, there have been no studies regarding the predictive nature of crowded living conditions on binge eating and the use of the Internet as coping strategies.

Methods

A total of 1048 Chinese college students (540 males and 508 females) were randomly selected and asked to complete a battery of questionnaires that included the Zung’s Self-Rating Anxiety Scale, the Internet Addiction Test, and Rosenbaum’s Self-Control Scale. Binge eating behaviors and compensatory behaviors were also reported, and variables about residential density were measured.

Results

Among female participants, binge eating scores were significantly predicted by anxiety caused by high-density living conditions (P = 0.008), and similarly, the frequency of compensatory behaviors was significantly predicted by anxiety caused by high-density living conditions (P = 0.000) and self-control (P = 0.003). Furthermore, the Internet Addiction Test scores were significantly predicted by the anxiety caused by high -density living conditions (P = 0.000) and self-control (P = 0.000). Among male participants, not only were the binge eating scores significantly predicted by the anxiety caused by high-density living conditions (P = 0.000) and self-control (P = 0.000), but the frequency of compensatory behaviors was also significantly predicted by the anxiety caused by high-density living conditions (P = 0.000) and self-control (P = 0.01). Furthermore, Internet Addiction Test scores were significantly predicted by anxiety caused by high-density living conditions (P = 0.000) and self-control (P = 0.000). It was further found that for both genders, subjective factors such as self-control, and the anxiety caused by high-density living conditions had a stronger impact on Internet addiction than objective factors, such as the size of the student’s dormitory room. Moreover, self-control was found to act as a moderator in the relationship between anxiety and Internet addiction among male participants.

Conclusion

Binge eating and Internet use could be considered coping strategies for Chinese college students facing high residential density in their dormitories.

Shared and unique mechanisms underlying binge eating disorder and addictive disorders

Scientific interest in "food addiction" is growing, but the topic remains controversial. One critique of "food addiction" is its high degree of phenotypic overlap with binge eating disorder (BED). In order to examine associations between problematic eating behaviors, such as binge eating and "food addiction," we propose the need to move past examining similarities and differences in symptomology. Instead, focusing on relevant mechanisms may more effectively determine whether "food addiction" contributes to disordered eating behavior for some individuals. This paper reviews the evidence for mechanisms that are shared (i.e., reward dysfunction, impulsivity) and unique for addiction (i.e., withdrawal, tolerance) and eating disorder (i.e., dietary restraint, shape/weight concern) frameworks. This review will provide a guiding framework to outline future areas of research needed to evaluate the validity of the "food addiction" model and to understand its potential contribution to disordered eating.

Interacting Neural Processes of Feeding, Hyperactivity, Stress, Reward, and the Utility of the Activity-Based Anorexia Model of Anorexia Nervosa

Anorexia nervosa (AN) is a psychiatric illness with minimal effective treatments and a very high rate of mortality. Understanding the neurobiological underpinnings of the disease is imperative for improving outcomes and can be aided by the study of animal models. The activity-based anorexia rodent model (ABA) is the current best parallel for the study of AN. This review describes the basic neurobiology of feeding and hyperactivity seen in both ABA and AN, and compiles the research on the role that stress-response and reward pathways play in modulating the homeostatic drive to eat and to expend energy, which become dysfunctional in ABA and AN.

The role of the opioid system in binge eating disorder

Binge eating disorder is characterized by excessive, uncontrollable consumption of palatable food within brief periods of time. Excessive intake of palatable food is thought to be driven by hedonic, rather than energy homeostatic, mechanisms. However, reward processing does not only comprise consummatory actions; a key component is represented by the anticipatory phase directed at procuring the reward. This phase is highly influenced by environmental food-associated stimuli, which can robustly enhance the desire to eat even in the absence of physiological needs. The opioid system (endogenous peptides and their receptors) has been strongly linked to the rewarding aspects of palatable food intake, and perhaps represents the key system involved in hedonic overeating. Here we review evidence suggesting that the opioid system can also be regarded as one of the systems that regulates the anticipatory incentive processes preceding binge eating hedonic episodes.

A daily diary study of perceived social isolation, dietary restraint, and negative affect in binge eating

Negative affect and dietary restraint are key predictors of binge eating, yet less is known about the impact of social factors on binge eating. The study sought to replicate and extend research on the relationships between negative affect, dietary restraint, perceived social isolation and binge eating using a daily diary methodology. College women (N = 54) completed measures of dietary restraint, negative affect, perceived social isolation, and binge eating daily for 14 days. Participants completed the measures nightly each day. A series of generalized estimating equations showed that dietary restraint was associated with less binge eating while controlling for negative affect and for perceived social isolation separately. Negative affect and perceived social isolation were associated with greater binge eating while controlling for restraint in separate analyses, but only perceived social isolation was significant when modeled simultaneously. All two-way interactions between negative affect, dietary restraint, and perceived social isolation predicting binge eating were nonsignificant. This study furthers our understanding of predictors of binge eating in a nonclinical sample. Specifically, these data suggest perceived social isolation, negative affect, and dietary restraint are important variables associated with binge eating in daily life and warrant further research.

Pharmacological approaches to the management of binge eating disorder

In the USA, binge eating disorder (BED) is the most common eating disorder, with a lifetime prevalence of ~3.5 % in adult women, 2.0 % in adult men, and 1.6 % in adolescents. BED is characterized by frequent episodes of binge eating that are accompanied by a sense of loss of control over eating and result in marked psychological distress. BED is highly co-morbid with obesity and with depression and other psychiatric conditions, and it is associated with substantial role impairment. Currently, there are no US FDA-approved pharmacological treatments for BED. Animal and human studies implicate underlying dysregulation in dopamine, opioid, acetylcholine, and serotonin neurocircuitry within brain reward regions in the pathogenesis and maintenance of BED. To date, the efficacy of various agents that target these and other neurotransmitter systems involved in motivated feeding behavior, mood regulation, and impulse control have been investigated in the treatment of BED. Several antidepressant and anticonvulsant agents have demonstrated efficacy in reducing binge eating frequency, but only in limited cases have these effects resulted in patients achieving abstinence, which is the primary goal of treatment; they also range from less (fluvoxamine) to more (topiramate) effective in achieving weight loss that is both clinically meaningful and significantly greater than placebo. Collectively, the literature on pharmacological treatment approaches to BED is limited in that very few agents have been studied in multiple, confirmatory trials with adequate follow up, and almost none have been evaluated in large patient samples that are diverse with respect to age, sex, and ethnicity. In addition, prior trials have not adequately addressed, through study design, the high placebo response commonly observed in this patient population. Several novel agents are in various phases of testing, and recent animal studies focusing on glutamate-signaling circuits linking the amygdala to the lateral hypothalamus offer new avenues for exploration and potential therapeutic development. Studies of newly FDA-approved medications for long-term obesity treatment and further explorations of dietary supplements and neutraceuticals with appetite- and mood-altering properties may also be worthwhile.

Two facets of stress and indirect effects on child diet through emotion-driven eating

OBJECTIVE

Stress has been associated with high-calorie, low-nutrient food intake (HCLN) and emotion-driven eating (EDE). However, effects on healthy food intake remain unknown. This study examined two facets of stress (self-efficacy, perceived helplessness) and food consumption, mediated by EDE.

METHODS

Cross-sectional data from fourth-graders (n=978; 52% female, 28% Hispanic) in an obesity intervention used self-report to assess self-efficacy, helplessness, EDE, fruit/vegetable (FV) intake, and high-calorie/low-nutrient (HCLN) food.

RESULTS

Higher stress self-efficacy was associated with higher FV intake, β=.354, p<0.001, and stress perceived helplessness had an indirect effect on HCLN intake through emotion-driven eating, indirect effect=.094, p<0.001; χ(2)(347)=659.930, p<0.001, CFI=0.940, TLI=0.930, RMSEA=0.030, p=1.00, adjusting for gender, ethnicity, BMI z-score, and program group.

CONCLUSIONS AND IMPLICATIONS

Stress self-efficacy may be more important for healthy food intake and perceived helplessness may indicate emotion-driven eating and unhealthy snack food intake. Obesity prevention programs may consider teaching stress management techniques to avoid emotion-driven eating.

Mice that gorged during dietary restriction increased foraging related behaviors and differed in their macronutrient preference when released from restriction

Caloric restriction (CR) can trigger gorging behavior. We examined macronutrient choice and behavior in mice that gorged during restriction compared to restricted non-gorgers and controls. Fifty MF1 male mice were restricted to 75% of ad-libitum food intake (FI), while ten controls were fed ad-lib. Body mass (BM) and FI were measured two and 24-h after food inclusion over 14-days. ‘Gorging’ mice were defined as those which ate over 25% of their daily FI in 2-h. The top 11 gorgers and the lowest 9 gorgers, along with 10 controls, had their behavior analysed during restriction, and were then provided with an unrestricted food choice, consisting of three diets that were high in fat, protein or carbohydrate. During restriction gorgers ate on average 51% of their daily FI in the 2-h following food introduction while the non-gorgers ate only 16%. Gorgers lost significantly more BM than non-gorgers possibly due to an increased physical activity linked to anticipation of daily food provision. Controls and non-gorgers spent most of their time sleeping. After restriction, both gorgers and non-gorgers were hyperphagic until their lost weight was regained. All 3 groups favoured high fat food. Gorgers and non-gorgers had a significantly greater high carbohydrate diet intake than controls, and gorgers also had a significantly greater high protein diet intake than non-gorgers and controls. On unrestricted food, they did not continue to gorge, although they still had a significantly greater 2-h FI than the other groups. Elevated protein intake may play an important role in the recovery of the lost lean tissue of gorgers after restriction.

When chocolate seeking becomes compulsion: gene-environment interplay

BACKGROUND

Eating disorders appear to be caused by a complex interaction between environmental and genetic factors, and compulsive eating in response to adverse circumstances characterizes many eating disorders.

MATERIALS AND METHODS

We compared compulsion-like eating in the form of conditioned suppression of palatable food-seeking in adverse situations in stressed C57BL/6J and DBA/2J mice, two well-characterized inbred strains, to determine the influence of gene-environment interplay on this behavioral phenotype. Moreover, we tested the hypothesis that low accumbal D2 receptor (R) availability is a genetic risk factor of food compulsion-like behavior and that environmental conditions that induce compulsive eating alter D2R expression in the striatum. To this end, we measured D1R and D2R expression in the striatum and D1R, D2R and α1R levels in the medial prefrontal cortex, respectively, by western blot.

RESULTS

Exposure to environmental conditions induces compulsion-like eating behavior, depending on genetic background. This behavioral pattern is linked to decreased availability of accumbal D2R. Moreover, exposure to certain environmental conditions upregulates D2R and downregulates α1R in the striatum and medial prefrontal cortex, respectively, of compulsive animals. These findings confirm the function of gene-environment interplay in the manifestation of compulsive eating and support the hypothesis that low accumbal D2R availability is a "constitutive" genetic risk factor for compulsion-like eating behavior. Finally, D2R upregulation and α1R downregulation in the striatum and medial prefrontal cortex, respectively, are potential neuroadaptive responses that parallel the shift from motivated to compulsive eating.

Chronic subordination stress induces hyperphagia and disrupts eating behavior in mice modeling binge-eating-like disorder

Background: Eating disorders are associated with physical morbidity and appear to have causal factors like stressful life events and negative affect. Binge-eating disorder (BED) is characterized by eating in a discrete period of time a larger than normal amount of food, a sense of lack of control over eating, and marked distress. There are still unmet needs for the identification of mechanisms regulating excessive eating, which is in part due to the lack of appropriate animal models. We developed a naturalistic murine model of subordination stress-induced hyperphagia associated with the development of obesity. Here, we tested the hypotheses that the eating responses of subordinate mice recapitulate the BED and that limiting hyperphagia could prevent stress-associated metabolic changes.

Methods: Adult male mice were exposed to a model of chronic subordination stress (CSS) associated with the automated acquisition of food intake and we performed a detailed meal pattern analysis. Additionally, using a pair-feeding protocol we tested the hypothesis that the manifestation of obesity and the metabolic syndrome could be prevented by limiting hyperphagia.

Results: The architecture of feeding of subordinate mice was disrupted during the stress protocol due to disproportionate amount of food ingested at higher rate and with shorter satiety ratio than control mice. Subordinate mice hyperphagia was further exacerbated in response to either hunger or to the acute application of a social defeat. Notably, the obese phenotype but not the fasting hyperglycemia of subordinate mice was abrogated by preventing hyperphagia in a pair-feeding paradigm.

Conclusion: Overall, these results support the validity of our CSS to model BED allowing for the determination of the underlying molecular mechanisms and the generation of testable predictions for innovative therapies, based on the understanding of the regulation and the control of food intake.

Prevalence of screening-detected eating disorders in chinese females and exploratory associations with dietary practices

OBJECTIVE

China is undergoing dramatic Westernization, hence may be able to provide unique insights into the role of sociocultural factors in disease. The purpose of this exploratory study was two-fold: to describe the prevalence of screening-detected eating disorders and disordered eating in China at the first occasion of assessment in the large-scale China Health and Nutrition Survey (CHNS) and to explore the associations between dietary practices and disordered eating. Regarding the first objective, participants are provincially representative and in subsequent waves will be followed longitudinally.

METHOD

CHNS participants were recruited using multistage, cluster random sampling, beginning in 1989. In this study, participants comprised 259 female adolescents (12-17 years) and 979 women (18-35 years) who participated in the CHNS 2009 survey, which is the first CHNS survey to assess disordered eating. Dietary practice-disordered eating associations were investigated with logistic regression adjusting for age, body mass index, and urbanization.

RESULTS

Of the participants, 6.3% (95% CI: 4.8, 8.2) of adults and 7.8% (95% CI: 5.0, 12.0) of adolescents had a screening-detected eating disorder. Dietary practices had non-significant associations with disordered eating at the general population level, except for protein consumption among women. There was evidence that skipping meals and a high-fat diet may confer risk.

DISCUSSION

Screening-detected eating disorders in China are lower in prevalence than in developed countries. Dietary practices had fairly limited associations with disordered eating at the general population level; protein consumption, skipping meals, and a high-fat diet are candidate dietary practice exposures for disordered eating. Copyright © 2014 John Wiley & Sons, Ltd and Eating Disorders Association.

A mouse model for binge-like sucrose overconsumption: Contribution of enhanced motivation for sweetener consumption

Behavioral and neural features of binge-like sugar overconsumption have been studied using rat models. However, few mouse models are available to examine the interaction between neural and genetic underpinnings of bingeing. In the present study, we first aim to establish a simple mouse model of binge-like sucrose overconsumption using daytime limited access training in food-restricted male mice. Trained mice received 4-h limited access to both 0.5M sucrose solution and chow for 10 days. Three control groups received (1) 4-h sucrose and 20-h chow access, (2) 20-h sucrose and 4-h, or (3) 20-h chow access, respectively. Only the trained group showed progressively increased sucrose consumption during brief periods of time and developed binge-like excessive behavior. Next, we examined whether the present mouse model mimicked a human feature of binge eating known as "eating when not physically hungry." Trained mice consumed significantly more sucrose or non-caloric sweetener (saccharin) during post-training days even after they nocturnally consumed substantial chow prior to daytime sweetener access. In other trained groups, both a systemic administration of glucose and substantial chow consumption prior to the daytime limited sucrose access failed to reduce binge-like sucrose overconsumption. Our results suggest that even when caloric consumption is not necessarily required, limited access training shapes and triggers binge-like overconsumption of sweetened solution in trained mice. The binge-like behavior in trained mice may be mainly due to enhanced hedonic motivation for the sweetener's taste. The present study suggests that our mouse model for binge-like sugar overconsumption may mimic some human features of binge eating and can be used to investigate the roles of neural and genetic mechanisms in binge-like overconsumption of sweetened substances in the absence of physical hunger.

Evidence for a compulsive-like behavior in rats exposed to alternate access to highly preferred palatable food

Converging evidence suggests that recurrent excessive calorie restriction causes binge eating by promoting behavioral disinhibition and overeating. This interpretation suggests that cognitive adaptations may surpass physiological regulations of metabolic needs after recurrent cycles of dieting and binging. Intermittent access to palatable food has long been studied in rats, but the consequences of such diet cycling procedures on the cognitive control of food seeking remain unclear. Female Wistar rats were divided in two groups matched for food intake and body weight. One group received standard chow pellets 7 days/week, whereas the second group was given chow pellets for 5 days and palatable food for 2 days over seven consecutive weeks. Rats were also trained for operant conditioning. Intermittent access to palatable food elicited binging behavior and reduced intake of normal food. Rats with intermittent access to palatable food failed to exhibit anxiety-like behaviors in the elevated plus maze, but displayed reduced locomotor activity in the open field and developed a blunted corticosterone response following an acute stress across the diet procedure. Trained under a progressive ratio schedule, both groups exhibited the same motivation for sweetened food pellets. However, in contrast to controls, rats with a history of dieting and binging exhibited a persistent compulsive-like behavior when access to preferred pellets was paired with mild electrical foot shock punishments. These results highlight the intricate development of anxiety-like disorders and cognitive deficits leading to a loss of control over preferred food intake after repetitive cycles of intermittent access to palatable food.

Animal models of compulsive eating behavior

Eating disorders are multifactorial conditions that can involve a combination of genetic, metabolic, environmental, and behavioral factors. Studies in humans and laboratory animals show that eating can also be regulated by factors unrelated to metabolic control. Several studies suggest a link between stress, access to highly palatable food, and eating disorders. Eating "comfort foods" in response to a negative emotional state, for example, suggests that some individuals overeat to self-medicate. Clinical data suggest that some individuals may develop addiction-like behaviors from consuming palatable foods. Based on this observation, "food addiction" has emerged as an area of intense scientific research. A growing body of evidence suggests that some aspects of food addiction, such as compulsive eating behavior, can be modeled in animals. Moreover, several areas of the brain, including various neurotransmitter systems, are involved in the reinforcement effects of both food and drugs, suggesting that natural and pharmacological stimuli activate similar neural systems. In addition, several recent studies have identified a putative connection between neural circuits activated in the seeking and intake of both palatable food and drugs. The development of well-characterized animal models will increase our understanding of the etiological factors of food addiction and will help identify the neural substrates involved in eating disorders such as compulsive overeating. Such models will facilitate the development and validation of targeted pharmacological therapies.

Pharmacological manipulations in animal models of anorexia and binge eating in relation to humans

Eating disorders, such as anorexia nervosa (AN), bulimia nervosa (BN) and binge eating disorders (BED), are described as abnormal eating habits that usually involve insufficient or excessive food intake. Animal models have been developed that provide insight into certain aspects of eating disorders. Several drugs have been found efficacious in these animal models and some of them have eventually proven useful in the treatment of eating disorders. This review will cover the role of monoaminergic neurotransmitters in eating disorders and their pharmacological manipulations in animal models and humans. Dopamine, 5-HT (serotonin) and noradrenaline in hypothalamic and striatal regions regulate food intake by affecting hunger and satiety and by affecting rewarding and motivational aspects of feeding. Reduced neurotransmission by dopamine, 5-HT and noradrenaline and compensatory changes, at least in dopamine D2 and 5-HT(2C/2A) receptors, have been related to the pathophysiology of AN in humans and animal models. Also, in disorders and animal models of BN and BED, monoaminergic neurotransmission is down-regulated but receptor level changes are different from those seen in AN. A hypofunctional dopamine system or overactive α2-adrenoceptors may contribute to an attenuated response to (palatable) food and result in hedonic binge eating. Evidence for the efficacy of monoaminergic treatments for AN is limited, while more support exists for the treatment of BN or BED with monoaminergic drugs.

Greater emotional eating scores associated with reduced frontolimbic activation to palatable taste in adolescents

OBJECTIVE

This study examined the relation between self-reported emotional eating scores and frontolimbic brain response to palatable taste in adolescents.

METHODS

Participants included 162 adolescents (mean BMI percentile = 52.7, range 3-90). Participants completed a self-report survey assessing emotional eating and underwent functional magnetic resonance imaging (fMRI) while viewing pictures signaling subsequent delivery of a chocolate milkshake or a control taste and receiving the corresponding taste.

RESULTS

Results revealed no significant relation between emotional eating scores and brain response to anticipation of receipt of milkshake. In response to milkshake taste receipt, emotional eating scores were negatively related to activation in the right thalamus, the left insula and orbitofrontal cortex, and bilateral putamen and caudate. These findings remained significant after controlling for body mass index and body fat percentage.

CONCLUSIONS

The current results are discussed in the context of findings of reduced reward activation to palatable taste receipt in obese adults and adolescents.

Sex differences in binge eating patterns in male and female adult rats

OBJECTIVE

Several efforts are underway to model binge eating in animals in order to advance neurobiological models of risk. However, knowledge of sex differences in these models is currently lacking. The goal of the present study was to examine sex differences in binge eating phenotypes using a well-established rodent model (i.e., the binge eating resistant/binge eating prone model).

METHOD

Thirty male and 30 female adult Sprague-Dawley rats were exposed to feeding tests consisting of intermittent access to palatable food (PF). Rats were then categorized as binge eating prone (BEP) based on the amount and consistency of PF consumption across tests.

RESULTS

Across multiple methods for BEP classification, rates of BEP phenotypes were two to six times higher in female than male rats.

DISCUSSION

Findings provide support for sex differences in rodent models of binge eating and highlight the promise of the BER/BEP model for understanding neurobiological mechanisms underlying sex differences in risk.

CRF-CRF1 receptor system in the central and basolateral nuclei of the amygdala differentially mediates excessive eating of palatable food

Highly palatable foods and dieting are major contributing factors for the development of compulsive eating in obesity and eating disorders. We previously demonstrated that intermittent access to palatable food results in corticotropin-releasing factor-1 (CRF1) receptor antagonist-reversible behaviors, which include excessive palatable food intake, hypophagia of regular chow, and anxiety-like behavior. However, the brain areas mediating these effects are still unknown. Male Wistar rats were either fed chow continuously for 7 days/week (Chow/Chow group), or fed chow intermittently 5 days/week, followed by a sucrose, palatable diet 2 days/week (Chow/Palatable group). Following chronic diet alternation, the effects of microinfusing the CRF1 receptor antagonist R121919 (0, 0.5, 1.5 μg/side) in the central nucleus of the amygdala (CeA), the basolateral nucleus of the amygdala (BlA), or the bed nucleus of the stria terminalis (BNST) were evaluated on excessive intake of the palatable diet, chow hypophagia, and anxiety-like behavior. Furthermore, CRF immunostaining was evaluated in the brain of diet cycled rats. Intra-CeA R121919 blocked both excessive palatable food intake and anxiety-like behavior in Chow/Palatable rats, without affecting chow hypophagia. Conversely, intra-BlA R121919 reduced the chow hypophagia in Chow/Palatable rats, without affecting excessive palatable food intake or anxiety-like behavior. Intra-BNST treatment had no effect. The treatments did not modify the behavior of Chow/Chow rats. Immunohistochemistry revealed an increased number of CRF-positive cells in CeA--but not in BlA or BNST--of Chow/Palatable rats, during both withdrawal and renewed access to the palatable diet, compared with controls. These results provide functional evidence that the CRF-CRF1 receptor system in CeA and BlA has a differential role in mediating maladaptive behaviors resulting from palatable diet cycling.

Arcuate nucleus homeostatic systems are not altered immediately prior to the scheduled consumption of large, binge-type meals of palatable solid or liquid diet in rats and Mice

Meal feeding is a critical issue in the over-consumption of calories leading to human obesity. To investigate the mechanisms involved in the regulation of meal feeding in rodents, we studied a scheduled feeding regime that induces substantial food intake over short periods of time. Male Sprague-Dawley rats and C57BL6 mice were fed one of four palatable diets [45% fat pellet, 60% fat pellet or standard pellet supplemented with Ensure (EN; Abbott Laboratories, Maidenhead, UK) or 12.5% sucrose (SUC)] either ad lib. or with daily 2-h scheduled access and standard pellet available for 22 h. Energy balance gene expression in the hypothalamic arcuate nucleus (ARC) and nucleus accumbens (NAcc) reward gene expression were assessed by in situ hybridisation. Rats fed ad lib. on 45% or 60% fat diet were heavier and fatter than controls, and had reduced neuropeptide Y (NPY) gene expression in the ARC. Mice fed ad lib. on any of the palatable diets were heavier, fatter and had higher blood leptin than controls, and had reduced NPY and increased cocaine- and-amphetamine-regulated transcript mRNA in the ARC. Schedule-fed rats and mice quickly adapted their feeding behaviour to 2-h access on palatable food. Three schedule-fed groups binged: the percentage of daily calories consumed in 2 h on 45% fat diet, 60% fat diet or EN, respectively, was 55%, 63% and 49% in rats, and 86%, 86% and 45% in mice. However, changed feeding behaviour was not reflected in an induction of orexigenic neuropeptide or suppression of anorexigenic neuropeptide gene expression in the ARC, in the 2-h period prior to scheduled feeding. The mechanisms underlying large meal/binge-type eating may be regulated by nonhomeostatic processes involving other genes in the hypothalamus or other brain areas. However, assessment of opioid and dopamine receptor gene expression in the NAcc did not reveal evidence of the involvement of these genes in driving large meals, at least at the investigated time point.

Adrenocortical regulation, eating in the absence of hunger and BMI in young children

The purpose of this study was to examine relations among adrenocortical regulation, eating in the absence of hunger, and body mass index (BMI) in children ages 5-9years (N=43). Saliva was collected before and after the Trier Social Stress Test for Children (TSST-C), and was later assayed for cortisol. Area under the curve with respect to increase (AUCi) was used as a measure of changes in cortisol release from baseline to 60min post-TSST-C. Age- and sex-specific BMI scores were calculated from measured height and weight, and eating in the absence of hunger was assessed using weighed food intake during a behavioral procedure. We also included a measure of parents' report of child impulsivity, as well as family demographic information. Participants were stratified by age into younger (5-7years) and older (8-9years) groups. In younger children, parents' reports of child impulsivity were significantly and positively associated with BMI; cortisol AUCi was not associated with BMI or eating in the absence of hunger. In older children, however, greater stress-related cortisol AUCi was related to higher BMI scores and greater energy intake in the absence of hunger. The results suggest that cortisol AUCi in response to psychosocial stress may be linked to problems with energy balance in children, with some variation by age.