The biology of binge eating

A mixed-methods longitudinal examination of weight-related self-monitoring and disordered eating among a population-based sample of emerging adults

BACKGROUND

Weight-related self-monitoring (WRSM) apps are used by millions, but the effects of their use remain unclear. This study examined longitudinal relationships between WRSM and disordered eating among a population-based sample of emerging adults.

METHODS

Participants (n = 138) were recruited from EAT 2010-2018 (Eating and Activity over Time study) to participate in a mixed-methods (quantitative and qualitative) longitudinal study to understand the impacts of WRSM. In 2018, participants (Mage=21.7 ± 1.9 years) reported motivations for use and types of WRSM apps used. Dependent variables collected in 2022 (Mage=25.7 ± 1.9 years) included past year total number of disordered weight control behaviors, disordered muscle building behaviors, compulsive exercise, and binge eating. Linear and logistic regressions were used adjusting for sociodemographics, body mass index, and baseline disordered eating. Semi-structured interviews (n = 25) were analyzed using inductive thematic analysis.

RESULTS

Participants using WRSM apps for weight management demonstrated an increase in disordered weight control behaviors over time (β = 0.894, p = .012). Using WRSM apps for "healthy" eating was marginally associated with an increase in disordered weight control behaviors. (β = 0.673, p = .052). Qualitatively, participants reported varied temporality between WRSM and disordered eating, but believed that app use encouraged restriction/binge cycles and normalized disordered eating.

CONCLUSIONS

Findings suggest there may be individual variation in the relationships between WRSM and disordered eating, but that using WRSM apps with the motivation of managing eating or weight may increase disordered eating in some. Additionally, WRSM apps may normalize or encourage disordered eating. Therefore, safeguards, including screening and monitoring, are needed to ensure WRSM does not cause or escalate harm among WRSM users.

1-Methyltryptophan treatment ameliorates high-fat diet-induced depression in mice through reversing changes in perineuronal nets

Depression and obesity are prevalent disorders with significant public health implications. In this study, we used a high-fat diet (HFD)-induced obese mouse model to investigate the mechanism underlying HFD-induced depression-like behaviors. HFD-induced obese mice exhibited depression-like behaviors and a reduction in hippocampus volume, which were reversed by treatment with an indoleamine 2,3-dioxygenase (IDO) inhibitor 1-methyltryptophan (1-MT). Interestingly, no changes in IDO levels were observed post-1-MT treatment, suggesting that other mechanisms may be involved in the anti-depressive effect of 1-MT. We further conducted RNA sequencing analysis to clarify the potential underlying mechanism of the anti-depressive effect of 1-MT in HFD-induced depressive mice and found a significant enrichment of shared differential genes in the extracellular matrix (ECM) organization pathway between the 1-MT-treated and untreated HFD-induced depressive mice. Therefore, we hypothesized that changes in ECM play a crucial role in the anti-depressive effect of 1-MT. To this end, we investigated perineuronal nets (PNNs), which are ECM assemblies that preferentially ensheath parvalbumin (PV)-positive interneurons and are involved in many abnormalities. We found that HFD is associated with excessive accumulation of PV-positive neurons and upregulation of PNNs, affecting synaptic transmission in PV-positive neurons and leading to glutamate-gamma-aminobutyric acid imbalances in the hippocampus. The 1-MT effectively reversed these changes, highlighting a PNN-related mechanism by which 1-MT exerts its anti-depressive effect.

The Effectiveness of Transcranial Direct Current Stimulation (tDCS) in Binge Eating Disorder (BED)-Review and Insight into the Mechanisms of Action

INTRODUCTION

Binge eating disorder (BED) is the most common eating disorder among those contributing to the development of obesity, and thus acts as a significant burden on the lives and health of patients. It is characterized by complex neurobiology, which includes changes in brain activity and neurotransmitter secretion. Existing treatments are moderately effective, and so the search for new therapies that are effective and safe is ongoing.

AIM AND METHODS

This review examines the use of transcranial direct current stimulation (tDCS) in the treatment of binge eating disorder. Searches were conducted on the PubMed/Medline, Research Gate, and Cochrane databases.

RESULTS

Six studies were found that matched the review topic. All of them used the anodal stimulation of the right dorsolateral prefrontal cortex (DLPFC) in BED patients. tDCS proved effective in reducing food cravings, the desire to binge eat, the number of binging episodes, and food intake. It also improved the outcomes of inhibitory control and the treatment of eating disorder psychopathology. The potential mechanisms of action of tDCS in BED are explained, limitations in current research are outlined, and recommendations for future research are provided.

CONCLUSIONS

Preliminary evidence suggests that the anodal application of tDCS to the right DLPFC reduces the symptoms of BED. However, caution should be exercised in the broader use of tDCS in this context due to the small number of studies performed and the small number of patients included. Future studies should incorporate neuroimaging and neurophysiological measurements to elucidate the potential mechanisms of action of tDCS in BED.

From gut microbiota to brain: implications on binge eating disorders

The prevalence of eating disorders has been increasing over the last 50 years. Binge eating disorder (BED) and bulimia nervosa (BN) are two typical disabling, costly and life-threatening eating disorders that substantially compromise the physical well-being of individuals while undermining their psychological functioning. The distressing and recurrent episodes of binge eating are commonly observed in both BED and BN; however, they diverge as BN often involves the adoption of inappropriate compensatory behaviors aimed at averting weight gain. Normal eating behavior is coordinated by a well-regulated trade-off between intestinal and central ingestive mechanism. Conversely, despite the fact that the etiology of BED and BN remains incompletely resolved, emerging evidence corroborates the notion that dysbiosis of gastrointestinal microbiome and its metabolites, alteration of gut-brain axis, as well as malfunctioning central circuitry regulating motivation, execution and reward all contribute to the pathology of binge eating. In this review, we aim to outline the current state of knowledge pertaining to the potential mechanisms through which each component of the gut-brain axis participates in binge eating behaviors, and provide insight for the development of microbiome-based therapeutic interventions that hold promise in ameliorating patients afflicted with binge eating disorders.

The Clinical Phenotype of Binge Eating Disorder among Postmenopausal Women: A Pilot Study

Binge eating disorder (BED), a form of overnutrition, may impact healthy aging for postmenopausal women. In community samples, 12-26% of older women (ages 60+) engage in binge eating. In younger adults, BED is comorbid with physical and psychological morbidities. However, little is known regarding the clinical phenotype, including medical and psychiatric comorbidities, of BED in postmenopausal women. This pilot study sought to identify psychosomatic, cardiometabolic, body composition, and physical function characteristics of postmenopausal, older adult (age ≥60 years) women with BED. Participants (N = 21, ages 60-75) completed a battery of physical assessments and surveys assessing psychosomatic health. Overall, 62% of women reported BE onset during peri- or post-menopause. Rates of comorbid depression, anxiety, sleep problems, and a history of severe menopausal symptoms were high. Cardiometabolic health was poor, and 42.9% met the criteria for metabolic syndrome. Additionally, 71.4% met the BMI criteria for obesity, and 40% of this sample met the criteria for sarcopenic obesity. Almost half of the sample presented with at least one mobility limitation; 85.7% had poor endurance. Evidence suggests that BED is highly comorbid with other chronic health conditions and may complicate treatment of these conditions, warranting further investigation and increased attention from healthcare providers serving postmenopausal women.

Maternal Over- and Malnutrition and Increased Risk for Addictive and Eating Disorders in the Offspring

Evidence from human and animal studies has shown that maternal overnutrition and/or obesity are linked with neurobehavioral changes in the offspring. This fetal programming is characterized by adaptive responses to changes in the nutritional state during early life. In the past decade, an association has been made between overconsumption of highly-palatable food by the mother during fetal development and abnormal behaviors resembling addiction in the offspring. Maternal overnutrition can lead to alterations in the offspring's brain reward circuitry leading to hyperresponsiveness of this circuit following exposure to calorie-dense foods later in life. Given the accumulating evidence indicating that the central nervous system plays a pivotal role in regulating food intake, energy balance, and the motivation to seek food, a dysfunction in the reward circuitry may contribute to the addiction-like behaviors observed in the offspring. However, the underlying mechanisms leading to these alterations in the reward circuitry during fetal development and their relevance to the increased risk for the offspring to later develop addictive-like behaviors is still unclear. Here, we review the most relevant scientific reports about the impact of food overconsumption during fetal development and its effect on addictive-like behaviors of the offspring in the context of eating disorders and obesity.

Eating disorder features in bipolar disorder: clinical implications

BACKGROUND

Bipolar disorder (BD) is associated with elevated rates of eating disorders (EDs), but the nature and impact of specific ED features are unclear.

AIMS

This study sought to identify which ED features are common in BD, and whether these relate to quality of life (QoL) impairment and body mass index (BMI).

METHOD

A clinical sample of 73 adults with BD completed self-report measures of health, ED features, emotion regulation ability, impulsivity, and QoL.

RESULTS

Binge eating (45%), excessive dietary restriction (39%), overvaluation of weight/shape (51%), purging (16%) and driven exercise (27%) were common, and associated with a poorer clinical picture, including poorer QoL and poorer emotion regulation. Furthermore, regular binge eating episodes explained a significant proportion of variance in QoL impairment after controlling for other significant predictors. The best predictors of BMI were number of medical conditions, impulsivity and positive beliefs about binge eating.

CONCLUSIONS

ED features that may not meet criteria for a fully diagnosable ED - particularly overvaluation of weight/shape and binge eating - warrant greater attention, as they may still significantly worsen QoL. Future research should focus on modifying existing psychological interventions to better target ED features among individuals with BD and thereby improve clinical outcomes.

The Association of Perceived Vulnerability to Disease with Cognitive Restraint and Compensatory Behaviors

Individual differences exist in perceived vulnerability to disease (PVD). PVD is associated with negative responses (e.g., disgust) towards individuals with obesity and heightened sensitivity regarding personal appearance. Through increasing fear of fat (FOF), PVD may be associated with cognitive restraint and compensatory behaviors. We utilized an adult sample (n = 247; 53.3% male sex assigned at birth) recruited through Amazon's MTurk prior to the COVID-19 pandemic to investigate associations between PVD, cognitive restraint and compensatory behaviors. Participants completed the Perceived Vulnerability to Disease Scale, Eating Disorder Diagnostic Scale, Dutch Eating Behaviors Questionnaire, and Goldfarb's Fear of Fat Scale. Mediation analyses were used to test our hypotheses. Perceived infectability (PVD-Infection) was associated with cognitive restraint and compensatory behaviors through increased FOF. Perceived germ aversion (PVD-Germ) was associated with cognitive restraint, but FOF did not mediate this association. Sex-stratified analyses revealed no significant sex differences. PVD may be an overlooked factor associated with cognitive restraint and compensatory behaviors in males and females. FOF was an important mediating factor in these associations. Increased engagement in cognitive restraint and compensatory behaviors may reflect attempts to reduce FOF. Future longitudinal research should explore whether PVD is a risk factor for cognitive restraint and compensatory behaviors.

Corticotropin-releasing factor system in the lateral septum: Implications in the pathophysiology of obesity

Obesity is a pandemic associated with lifestyles changes. These include excess intake of obesogenic foods and decreased physical activity. Brain areas, like the lateral hypothalamus (LH), ventral tegmental area (VTA), and nucleus accumbens (NAcc) have been linked in both homeostatic and hedonic control of feeding in experimental models of diet-induced obesity. Interestingly, these control systems are regulated by the lateral septum (LS), a relay of γ-aminobutyric (GABA) acid neurons (GABAergic neurons) that inhibit the LH and GABAergic interneurons of the VTA. Furthermore, the LS has a diverse receptor population for neurotransmitters and neuropeptides such as dopamine, glutamate, GABA and corticotropin-releasing factor (CRF), among others. Particularly, CRF a key player in the stress response, has been related to the development of overweight and obesity. Moreover, evidence shows that LS neurons neurophysiologically regulate reward and stress, although there is little evidence of LS taking part in homeostatic and hedonic feeding. In this review, we discuss the evidence that supports the role of LS and CRF on feeding, and how alterations in this system contribute to weight gain obesity.

Decreased excitability of leptin-sensitive anterior insula pyramidal neurons in a rat model of compulsive food demand

Compulsive eating is an overlapping construct with binge eating that shares many characteristics with substance use disorders. Compulsive eating may impact millions of Americans; presenting in some cases of binge eating disorders, overweight/obesity, and among individuals who have not yet been diagnosed with a recognized eating disorder. To study the behavioral and neurobiological underpinnings of compulsive eating, we employ a published rodent model using cyclic intermittent access to a palatable diet to develop a self-imposed binge-withdrawal cycle. Here, we further validated this model of compulsive eating in female Wistar rats, through the lens of behavioral economic analyses and observed heightened demand intensity, inelasticity and essential value as well as increased food-seeking during extinction. Using electrophysiological recordings in the anterior insular cortex, a region previously implicated in modulating compulsive-like eating in intermittent access models, we observed functional adaptations of pyramidal neurons. Within the same neurons, application of leptin led to further functional adaptations, suggesting a previously understudied, extrahypothalamic role of leptin in modulating feeding-related cortical circuits. Collectively, the findings suggest that leptin may modulate food-related motivation or decision-making via a plastic cortical circuit that is influenced by intermittent access to a preferred diet. These findings warrant further study of whether behavioral economics analysis of compulsive eating can impact disordered eating outcomes in humans and of the translational relevance of a leptin-sensitive anterior insular circuit implicated in these behaviors.

Modified Dual Pathway Model for Binge Eating: The Role of Emotion Dysregulation

We tested a modification of the dual pathway model using two sequential mediators between body dissatisfaction and binge eating: restricted eating and difficulties in emotion regulation replacing negative affect. A total of 435 college students completed an online survey. Results from path analyses indicated that the relationship between body dissatisfaction and binge eating was not mediated by restricted eating for neither women nor men. However, this relationship was mediated first by restricted eating and then by difficulties in emotion regulation for women only. Moreover, this relationship was mediated by difficulties in emotion regulation for both women and men. A post hoc analysis indicated that the above mediation results were still significant after adding negative affect into the model. No mediations through negative affect were significant. Clinical implications include the conceptualization and intervention of eating concerns within an emotion dysregulation framework.

The physiological control of eating: signals, neurons, and networks

During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.

Individuals Diagnosed with Binge-Eating Disorder Have DNA Hypomethylated Sites in Genes of the Metabolic System: A Pilot Study

Binge-eating disorder, recently accepted as a diagnostic category, is differentiated from bulimia nervosa in that the former shows the presence of binge-eating episodes and the absence of compensatory behavior. Epigenetics is a conjunct of mechanisms (like DNA methylation) that regulate gene expression, which are dependent on environmental changes. Analysis of DNA methylation in eating disorders shows that it is reduced. The present study aimed to analyze the genome-wide DNA methylation differences between individuals diagnosed with BED and BN. A total of 46 individuals were analyzed using the Infinium Methylation EPIC array. We found 11 differentially methylated sites between BED- and BN-diagnosed individuals, with genome-wide significance. Most of the associations were found in genes related to metabolic processes (ST3GAL4, PRKAG2, and FRK), which are hypomethylated genes in BED. Cg04781532, located in the body of the PRKAG2 gene (protein kinase AMP-activated non-catalytic subunit gamma 2), was hypomethylated in individuals with BED. Agonists of PRKAG2, which is the subunit of AMPK (AMP-activated protein kinase), are proposed to treat obesity, BED, and BN. The present study contributes important insights into the effect that BED could have on PRKAG2 activation.

The Role of the Gut Microbiome, Immunity, and Neuroinflammation in the Pathophysiology of Eating Disorders

There is a growing recognition that both the gut microbiome and the immune system are involved in a number of psychiatric illnesses, including eating disorders. This should come as no surprise, given the important roles of diet composition, eating patterns, and daily caloric intake in modulating both biological systems. Here, we review the evidence that alterations in the gut microbiome and immune system may serve not only to maintain and exacerbate dysregulated eating behavior, characterized by caloric restriction in anorexia nervosa and binge eating in bulimia nervosa and binge eating disorder, but may also serve as biomarkers of increased risk for developing an eating disorder. We focus on studies examining gut dysbiosis, peripheral inflammation, and neuroinflammation in each of these eating disorders, and explore the available data from preclinical rodent models of anorexia and binge-like eating that may be useful in providing a better understanding of the biological mechanisms underlying eating disorders. Such knowledge is critical to developing novel, highly effective treatments for these often intractable and unremitting eating disorders.

Breaking It Down: Investigation of Binge Eating Components in Animal Models to Enhance Translation

Binge eating (BE) is a core eating disorder behavior that is present across nearly all eating disorder diagnoses (e. g., bulimia nervosa, binge eating disorder, anorexia nervosa binge/purge subtype), and is also widely present in the general population. Despite the prevalence of BE, limited treatment options exist and there are often high rates of relapse after treatment. There is evidence showing that genetic factors contribute to the heritability of BE and support for biological contributions to BE. However, more work is needed to fully understand neurobiological mechanisms underlying BE. One approach to target this problem is to separate BE into its distinct clinical components that can be more easily modeled using pre-clinical approaches. To date, a variety of animal models for BE have been used in pre-clinical studies; but there have been challenges translating this work to human BE. Here, we review these pre-clinical approaches by breaking them down into three clinically-significant component parts (1) consumption of a large amount of food; (2) food consumption within a short period of time; and (3) loss of control over eating. We propose that this rubric identifies the most frequently used and effective ways to model components of BE behavior using pre-clinical approaches with the strongest clinical relevance. Finally, we discuss how current pre-clinical models have been integrated with techniques using targeted neurobiological approaches and propose ways to improve translation of pre-clinical work to human investigations of BE that could enhance our understanding of BE behavior.

Diet, Stress and Mental Health

Introduction: There has long been an interest in the effects of diet on mental health, and the interaction of the two with stress; however, the nature of these relationships is not well understood. Although associations between diet, obesity and the related metabolic syndrome (MetS), stress, and mental disorders exist, causal pathways have not been established. Methods: We reviewed the literature on the relationship between diet, stress, obesity and psychiatric disorders related to stress. Results: Diet and obesity can affect mood through direct effects, or stress-related mental disorders could lead to changes in diet habits that affect weight. Alternatively, common factors such as stress or predisposition could lead to both obesity and stress-related mental disorders, such as depression and posttraumatic stress disorder (PTSD). Specific aspects of diet can lead to acute changes in mood as well as stimulate inflammation, which has led to efforts to assess polyunsaturated fats (PUFA) as a treatment for depression. Bidirectional relationships between these different factors are also likely. Finally, there has been increased attention recently on the relationship between the gut and the brain, with the realization that the gut microbiome has an influence on brain function and probably also mood and behavior, introducing another way diet can influence mental health and disorders. Brain areas and neurotransmitters and neuropeptides that are involved in both mood and appetite likely play a role in mediating this relationship. Conclusions: Understanding the relationship between diet, stress and mood and behavior could have important implications for the treatment of both stress-related mental disorders and obesity.

Associations Between Approach and Avoidance Coping, Psychological Distress, and Disordered Eating Among Candidates for Bariatric Surgery

BACKGROUND

Individuals seeking bariatric surgery evidence risk for binge and disordered eating behaviors, which can lead to poorer post-surgical weight loss outcomes. Use of avoidant coping strategies to manage stress, along with symptoms of depression, are associated with disordered eating in the general population. However, the role of coping has not been examined among candidates for bariatric surgery, and coping and depression have rarely been considered in combination. Given the emerging standard that psychologists are involved in evaluations and treatment before and after surgery, consideration of these variables is clinically relevant.

METHODS

Participants were 399 patients undergoing pre-surgical bariatric psychological assessment. Hierarchical linear regression analyses tested whether gender, age, and BMI; approach and avoidance coping; and depression and anxiety were associated with disordered eating (binge eating, restraint, eating concerns, shape concerns, weight concerns) in a cross-sectional study design.

RESULTS

In initial steps of the model controlling demographic variables, approach coping predicted less and avoidance coping predicted more disordered eating across most outcomes examined. In models including depression and anxiety, avoidance (but not approach) coping remained a relevant predictor. The effects of depression were also quite robust, such that participants who were more depressed reported more disordered eating. More anxious participants reported more restrained eating.

CONCLUSIONS

Avoidance coping and depressive symptoms emerged as key variables in understanding recent disordered eating among patients considering bariatric surgery. Pre-surgical psychological evaluations and treatment approaches could be enhanced with consideration of patient coping strategies, particularly avoidant coping responses to stress, independent of psychological distress.

A double-blind, placebo-controlled study of vortioxetine in the treatment of binge-eating disorder

BACKGROUND

Binge-eating disorder (BED) is associated with impaired quality of life and has a number of untoward public health associations. There are few established pharmacological treatments for BED, and available options are not suitable for all individuals. Vortioxetine is a recently developed pharmacological agent with effects on the serotonergic but also other neurochemical systems, which has yet to be evaluated in this context.

METHOD

Eighty adults with BED were recruited for a double-blind, placebo-controlled study. Participants received 12-week treatment with vortioxetine (10 mg/day for 1 week, then increasing to 20 mg/day) or placebo in a parallel design. The primary efficacy outcome measures were binge-eating frequency and weight. Safety data were collected. Effects of active versus placebo treatment were characterized using linear repeated measures models.

RESULTS

Both vortioxetine and placebo treatment were associated with significant reductions in binge-eating frequency. Vortioxetine did not differentiate significantly from placebo on any efficacy measure. Frequency of adverse events did not differ between groups.

DISCUSSION

Vortioxetine was not more effective than placebo in the treatment of BED. The ability to detect pharmacological treatment benefit may have been hindered by the relatively high placebo response and drop out. Future work should seek to better understand and predict placebo response in BED, with a view to more targeted treatment interventions and, potentially, sample enrichment.

Role of eating disorders-related polymorphisms in obesity pathophysiology

Human biological system provides innumerable neuroendocrine inputs for food intake control, with effects on appetite's modulation and the satiety signs. Its regulation is very complex, engaging several molecular interactions with many tissues, hormones, and neural circuits. Thus, signaling molecules that control food intake are critical for normal energy homeostasis and a deregulation of these pathways can lead to eating disorders and obesity. In line of this, genetic factors have a significantly influence of the regulation of neural circuits controlling the appetite and satiety pathways, as well as the regulation of brain reward systems. Single Nucleotide Polymorphisms (SNPs) in genes related to hypothalamic appetite and satiety mechanisms, further in multiple neurotransmitter systems may contribute to the development of major Eating Disorders (EDs) related to obesity, among them Binge Eating Disorder (BED) and Bulimia Nervosa (BN), which are discussed in this review.

A randomized comparison of long acting methylphenidate and cognitive behavioral therapy in the treatment of binge eating disorder

Cognitive behavioral therapy (CBT) is a well-established treatment for binge eating disorder (BED); however, this treatment is underutilized, highlighting the need for additional treatment alternatives. Dopamine neurotransmission has been associated with dysregulated eating, and pharmaceutical agents targeting the dopamine system are associated with decreased binge eating and weight. The primary objective of the current investigation was to evaluate the efficacy of psychostimulant medication versus current best practices in the treatment of BED symptoms, in a randomized trial of methylphenidate versus CBT for BED. The secondary objective was to evaluate the ability of impulsivity to predict treatment outcomes. Female outpatients with BED were randomized to receive methylphenidate (n = 22) or CBT (n = 27) for 12 weeks. The primary outcome was objective binge episode frequency; secondary outcomes included subjective binge episode frequency, body mass index (BMI), BED symptoms, and quality of life. Results showed that both treatments had a significant impact on primary and secondary outcomes. Methylphenidate and CBT were associated with decreases in subjective and objective binge episodes; methylphenidate was associated with greater decreases in BMI. Two impulsivity traits predicted clinical outcomes. Results provide preliminary support for the therapeutic benefit of methylphenidate in BED treatment, and prognostic utility of impulsivity in this context.

Sufficient intake of high-fat food attenuates stress-induced social avoidance behavior

AIMS

Psychosocial stress is a form of mental stress associated with human relationships that underlies the pathogenesis of mental disorders such as depression. Previous studies have suggested that intake of energy-dense foods, also known as "palatable foods," can relieve psychosocial stress. However, it remains unclear whether the volume of palatable food affects abnormal behavior induced by psychosocial stress. In the present study, we aimed to determine whether levels of high-fat food intake significantly influence psychosocial stress using the social-defeat stress (SDS) paradigm.

MAIN METHODS

Mice subjected to SDS ate either a high-fat or normal chow diet for 10 days. Behavioral tests were conducted following the completion of the SDS paradigm. The hypothalamus, liver, and blood were examined post-mortem.

KEY FINDINGS

Mice with sufficient intake of high-fat chow immediately following exposure to SDS did not exhibit social avoidance behavior, suggesting that a high-fat diet may improve social behavior. However, inadequate intake of high-fat food, which did not alter cholesterol metabolism or hypothalamic-pituitary-adrenal axis activity, was not associated with such benefits, instead increased anxiety-like behavior.

SIGNIFICANCE

The results of the present study demonstrate that eating a high-fat diet may attenuate stress, but that this benefit disappears with insufficient intake of high-fat foods. The benefits of a high-fat diet under SDS may be related to cholesterol metabolism in the liver.

Transcriptional regulation of the endocannabinoid system in a rat model of binge-eating behavior reveals a selective modulation of the hypothalamic fatty acid amide hydrolase gene

OBJECTIVE

Binge-eating episodes are recurrent and are defining features of several eating disorders. Thus binge-eating episodes might influence eating disorder development of which exact underlying mechanisms are still largely unknown.

METHODS

Here we focused on the transcriptional regulation of the endocannabinoid system, a potent regulator of feeding behavior, in relevant rat brain regions, using a rat model in which a history of intermittent food restriction and a frustration stress induce binge-like palatable food consumption.

RESULTS

We observed a selective down-regulation of fatty acid amide hydrolase (faah) gene expression in the hypothalamus of rats showing the binge-eating behavior with a consistent reduction in histone 3 acetylation at lysine 4 of the gene promoter. No relevant changes were detected for any other endocannabinoid system components in any brain regions under study, as well as for the other epigenetic mechanisms investigated (DNA methylation and histone 3 lysine 27 methylation) at the faah gene promoter.

DISCUSSION

Our findings suggest that faah transcriptional regulation is a potential biomarker of binge-eating episodes, with a relevant role in the homeostatic regulation of food intake.

Cocaine- and amphetamine-regulated transcript (CART): A multifaceted neuropeptide

Over the last 35 years, the continuous discovery of novel neuropeptides has been the key to the better understanding of how the central nervous system has integrated with neuronal signals and behavioral responses. Cocaine and amphetamine-regulated transcript (CART) was discovered in 1995 in the rat striatum but later was found to be highly expressed in the hypothalamus. The widespread distribution of CART peptide in the brain complicated the understanding of the role played by this neurotransmitter. The main objective of the current compact review is to piece together the fragments of available information about origin, expression, distribution, projection, and function of CART peptides. Accumulative evidence suggests CART as a neurotransmitter and neuroprotective agent that is mainly involved in regulation of feeding, addiction, stress, anxiety, innate fear, neurological disease, neuropathic pain, depression, osteoporosis, insulin secretion, learning, memory, reproduction, vision, sleep, thirst and body temperature. In spite of the vast number of studies about the CART, the overall pictures about the CART functions are sketchy. First, there is a lack of information about cloned receptor, specific agonist and antagonist. Second, CART peptides are detected in discrete sets of neurons that can modulate countless activities and third; CART peptides exist in several fragments due to post-translational processing. For these reasons the overall picture about the CART peptides are sketchy and confounding.

[Genetics factors in pathogenesis and clinical genetics of binge eating disorder]

Genetic studies have shown that binge eating disorder (ВЕD) aggregates in families, heritability was estimated as about 60% and additive genetic influences on BED up to 50%. Using a genetic approach has proved useful for verifying the diagnostic categories of BED using DSM-IV criteria and supporting the validity of considering this pathology as a separate nosological category. The results confirmed the genetic and pathogenic originality of BED as a separate psychopathological phenomenon, but not a subtype of obesity. It seems fruitful to considerate BED as a disease with hereditary predisposition with significant genetic influence and a complex psychopathological syndrome, including not only eating disorders, but also depressive and addictive component. A possible mechanism of pathogenesis of BED may be the interaction of the neuroendocrine and neurotransmitters systems including the active involvement of the reward system in response to a variety of chronic stress influences with the important modulatory role of specific personality traits. The high level of genetic influence on the certain clinical manifestations of BED confirms the ability to identify the subphenotypes of BED on genetic basis involving clinical criteria. It can not only contribute to further genetic studies, taking into account more homogeneous samples, but also help in finding differentiated therapeutic approaches.

The duration of intermittent access to preferred sucrose-rich food affects binge-like intake, fat accumulation, and fasting glucose in male rats

Many people restrict their palatable food intake. In animal models, time-limiting access to palatable foods increases their intake while decreasing intake of less preferred alternatives; negative emotional withdrawal-like behavior is sometimes reported. In drug addiction models, intermittent extended access drives greater changes in use than brief access. When it comes to palatable food, the impact of briefer vs. longer access durations within intermittent access conditions remains unclear. Here, we provided male rats with chow or with weekday access to a preferred, sucrose-rich diet (PREF) (2, 4, or 8 h daily) with chow otherwise available. Despite normal energy intake, all restricted access conditions increased weight gain by 6 weeks and shifted diet acceptance within 1 week. They increased daily and 2-h intake of PREF with individual vulnerability and decreased chow intake. Rats with the briefest access had the greatest binge-like (2-h) intake, did not lose weight on weekends despite undereating chow, and were fattier by 12 weeks. Extended access rats (8 h) showed the greatest daily intake of preferred food and corresponding undereating of chow, slower weight gain when PREF was unavailable, and more variable daily energy intake from week to week. Increased fasting glucose was seen in 2-h and 8-h access rats. During acute withdrawal from PREF to chow diet, restricted access rats showed increased locomotor activity. Thus, intermittent access broadly promoted weight gain, fasting hyperglycemia and psychomotor arousal during early withdrawal. More restricted access promoted greater binge-like intake and fat accumulation, whereas longer access promoted evidence of greater food reward tolerance.

Intermittent, extended access to preferred food leads to escalated food reinforcement and cyclic whole-body metabolism in rats: Sex differences and individual vulnerability

Compulsive binge eating is a hallmark of binge eating disorder and bulimia nervosa and is implicated in some obesity cases. Eating disorders are sexually dimorphic, with females more often affected than males. Animal models of binge-like eating based on intermittent access to palatable food exist; but, little is known regarding sex differences or individual vulnerability in these models with respect to the reinforcing efficacy of food, the development of compulsive- and binge-like eating, or associated changes in whole-body metabolism or body composition. Adolescent male (n = 24) and female (n = 32) Wistar rats were maintained on chow or a preferred, high-sucrose, chocolate-flavored diet in continuous or intermittent, extended access conditions. Body weight and composition, intake, fixed- and progressive-ratio operant self-administration, and whole body energy expenditure and respiratory exchange ratios were measured across an 11-week study period. Subgroup analyses were conducted to differentiate compulsive-like "high responder" intermittent access rats that escalated to extreme progressive-ratio self-administration performance vs. more resistant "low responders." Female rats had greater reinforcing efficacy of food than males in all diet conditions and were more often classified as "high responders". In both sexes, rats with intermittent access showed cycling of fuel substrate utilization and whole-body energy expenditure. Further, "high-responding" intermittent access female rats had especially elevated respiratory exchange ratios, indicating a fat-sparing phenotype. Future studies are needed to better understand the molecular and neurobiological basis of the sex and individual differences we have observed in rats and their translational impact for humans with compulsive, binge eating disorders.

A spontaneous binge-like eating model in mice using unpredictable once weekly access to palatable diets

Many pre-clinical models of binge-like eating involve predictable, scheduled, access to a palatable diet high in fat (HF), where access may be preceded by anticipatory behaviour. Here, to introduce spontaneity into the binge-type consumption of palatable diets, mice were allowed 2 h access on a random day once per week and at a random time within an 8 h window either side of the transition from dark phase to light phase. Despite normal intake of a stock diet prior to unpredictable access to HF diet, mice immediately initiated a substantial eating episode when presented with HF diet. Following this consumption, compensatory hypophagia was observed relative to stock diet-fed controls, and cumulative energy intakes converged. There were no effects of HF diet on body weight or body composition over a 12-week period. Binge-like consumption was also observed on unpredictable access to the complete liquid diet, chocolate Ensure, but not with a 10% sucrose solution. Binge-like responses to unpredictable access to HF diet or Ensure were similar in male and female mice, although there were effects of sex on caloric consumption from stock diet in the compensatory period following palatable diet intake, with higher intakes in females. The timing of the 2h access period relative to light phase transition affected intake of palatable diets, but less robustly than the equivalent effect on stock diet intake during the same timed periods - the diurnal patterning of energy intake was diet sensitive. The large spontaneous binge-like consumption on unpredictable access to either solid or liquid palatable diets in mice of either sex offers the potential to combine these attributes with other manipulations where a developing obesity is part of the binge-like eating phenotype.

Eating disorders in premenstrual dysphoric disorder: a neuroendocrinological pathway to the pathogenesis and treatment of binge eating

BACKGROUND

This case report details the presentation, treatment and post-operative outcome of an adult female with co-occurring binge eating disorder and premenstrual dysphoric disorder (PMDD).

CASE PRESENTATION

The patient, self-presenting for treatment, reported having struggled with severe, debilitating physical and psychological PMDD symptoms for nearly a decade. After having taken part in a number of unsuccessful first- and second line treatments in primary and secondary care, the patient was referred to tertiary care at the Department of Gynecology at Oslo University Hospital in Norway. Chemical menopause using a gonadotropin-releasing hormone (GnRH) agonist was induced, predicting the desired response (i.e. resolution of PMDD symptoms) to bilateral salpingo-oophorectomy (BSO). At three- and six months post BSO follow-up, the patient reported complete resolution of all reported PMDD symptoms including marked increase in appetite (i.e. hyperphagia), specific food cravings and auxiliary binge eating.

CONCLUSIONS

To our knowledge, this is the first case documenting the recovery from an eating disorder following surgical ovarian suppression. Our findings lend supports to existing studies linking binge eating to hormonal changes in the mid-luteal phase of the menstrual cycle, and may help advance new treatment options for a selected, severely impaired group of females struggling with excessive appetite and binge eating due to fluctuations in ovarian activity.

Hypothalamic CRF1 receptor mechanisms are not sufficient to account for binge-like palatable food consumption in female rats

OBJECTIVE

The present study evaluated the effect of systemic injection of the CRF1 receptor antagonist R121919, the corticosterone synthesis inhibitor metyrapone and central amygdala (CeA) injections of the nonselective CRF antagonist D-Phe-CRF_(12-41) in rats in which binge eating was evoked by stress and cycles of food restriction.

METHOD

Female rats were subjected or not to repeated cycles of regular chow food restriction/ad libitum feeding during which they were also given limited access (2 h) to palatable food. On the test day, rats were either exposed or not to the sight of the palatable food for 15 min without allowing access, before assessing food consumption.

RESULTS

Systemic injections of R121919, but not of the metyrapone, blocked binge-like eating behavior. Restricted and stressed rats showed up-regulation of crh1 receptor mRNA signal in the bed nucleus of the stria terminalis and CeA but not in basolateral amygdala (BLA) or in the paraventricular nucleus. Injection D-Phe-CRF_(12-41) in CeA but not in the BLA-blocked binge-like eating behavior.

DISCUSSION

These findings demonstrate that extra-hypothalamic CRF1 receptors, rather than those involved in endocrine functions, are involved in binge eating and the crucial role of CRF receptors in CeA. CRF1 receptor antagonism may represent a novel pharmacological treatment for binge-related eating disorders.

Cognitive impairment and gene expression alterations in a rodent model of binge eating disorder

Binge eating disorder (BED) is defined as recurrent, distressing over-consumption of palatable food (PF) in a short time period. Clinical studies suggest that individuals with BED may have impairments in cognitive processes, executive functioning, impulse control, and decision-making, which may play a role in sustaining binge eating behavior. These clinical reports, however, are limited and often conflicting. In this study, we used a limited access rat model of binge-like behavior in order to further explore the effects of binge eating on cognition. In binge eating prone (BEP) rats, we found novel object recognition (NOR) as well as Barnes maze reversal learning (BM-RL) deficits. Aberrant gene expression of brain derived neurotrophic factor (Bdnf) and tropomyosin receptor kinase B (TrkB) in the hippocampus (HPC)-prefrontal cortex (PFC) network was observed in BEP rats. Additionally, the NOR deficits were correlated with reductions in the expression of TrkB and insulin receptor (Ir) in the CA3 region of the hippocampus. Furthermore, up-regulation of serotonin-2C (5-HT_2C) receptors in the orbitoprefrontal cortex (OFC) was associated with BM-RL deficit. Finally, in the nucleus accumbens (NAc), we found decreased dopamine receptor 2 (Drd2) expression among BEP rats. Taken together, these data suggest that binge eating vegetable shortening may induce contextual and reversal learning deficits which may be mediated, at least in part, by the altered expression of genes in the CA3-OFC-NAc neural network.

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.

A Single Day of Excessive Dietary Fat Intake Reduces Whole-Body Insulin Sensitivity: The Metabolic Consequence of Binge Eating

Consuming excessive amounts of energy as dietary fat for several days or weeks can impair glycemic control and reduce insulin sensitivity in healthy adults. However, individuals who demonstrate binge eating behavior overconsume for much shorter periods of time; the metabolic consequences of such behavior remain unknown. The aim of this study was to determine the effect of a single day of high-fat overfeeding on whole-body insulin sensitivity. Fifteen young, healthy adults underwent an oral glucose tolerance test before and after consuming a high-fat (68% of total energy), high-energy (78% greater than daily requirements) diet for one day. Fasting and postprandial plasma concentrations of glucose, insulin, non-esterified fatty acids, and triglyceride were measured and the Matsuda insulin sensitivity index was calculated. One day of high-fat overfeeding increased postprandial glucose area under the curve (AUC) by 17.1% (p < 0.0001) and insulin AUC by 16.4% (p = 0.007). Whole-body insulin sensitivity decreased by 28% (p = 0.001). In conclusion, a single day of high-fat, overfeeding impaired whole-body insulin sensitivity in young, healthy adults. This highlights the rapidity with which excessive consumption of calories through high-fat food can impair glucose metabolism, and suggests that acute binge eating may have immediate metabolic health consequences for the individual.

Estrogenic suppression of binge-like eating elicited by cyclic food restriction and frustrative-nonreward stress in female rats

Because binge eating and emotional eating vary through the menstrual cycle in human females, we investigated cyclic changes in binge-like eating in female rats and their control by estrogens. Binge-like eating was elicited by three cycles of 4 days of food restriction and 4 days of free feeding followed by a single frustrative nonreward-stress episode (15 min visual and olfactory exposure to a familiar palatable food) immediately before presentation of the palatable food. Intact rats showed binge-like eating during the diestrous and proestrous phases of the ovarian cycle, but not during the estrous (periovulatory) phase. Ovariectomized (OVX) rats not treated with estradiol (E2) displayed binge-like eating, whereas E2-treated OVX rats did not. The procedure did not increase signs of anxiety in an open-field test. OVX rats not treated with E2 that were subjected to food restriction and sacrificed immediately after frustrative nonreward had increased numbers of cells expressing phosphorylated extracellular signal-regulated kinases (ERK) in the central nucleus of the amygdala (CeA), paraventricular nucleus of hypothalamus (PVN), and dorsal and ventral bed nuclei of the stria terminalis (BNST) compared with nonrestricted or E2-treated rats. These data suggest that this female rat model is appropriate for mechanistic studies of some aspects of menstrual-cycle effects on emotional and binge eating in human females, that anxiety is not a sufficient cause of binge-like eating, and that the PVN, CeA, and BNST may contribute to information processing underlying binge-like eating.

Stress, overeating, and obesity: Insights from human studies and preclinical models

Eating disorders and obesity have become predominant in human society. Their association to modern lifestyle, encompassing calorie-rich diets, psychological stress, and comorbidity with major diseases are well documented. Unfortunately the biological basis remains elusive and the pharmacological treatment inadequate, in part due to the limited availability of valid animal models. Human research on binge eating disorder (BED) proves a strong link between stress exposure and bingeing: state-levels of stress and negative affect are linked to binge eating in individuals with BED both in laboratory settings and the natural environment. Similarly, classical animal models of BED reveal an association between acute exposure to stressors and binging but they are often associated with unchanged or decreased body weight, thus reflecting a negative energy balance, which is uncommon in humans where most commonly BED is associated with excessive or unstable body weight gain. Recent mouse models of subordination stress induce spontaneous binging and hyperphagia, altogether more closely mimicking the behavioral and metabolic features of human BED. Therefore the translational relevance of subordination stress models could facilitate the identification of the neurobiological basis of BED and obesity-associated disease and inform on the development of innovative therapies.

Acute ghrelin changes food preference from a high-fat diet to chow during binge-like eating in rodents

Ghrelin, an orexigenic hormone released from the empty stomach, provides a gut-brain signal that promotes many appetitive behaviours, including anticipatory and goal-directed behaviours for palatable treats high in sugar and/or fat. In the present study, we aimed to determine whether ghrelin is able to influence and/or may even have a role in binge-like eating behaviour in rodents. Accordingly, we used a palatable scheduled feeding (PSF) paradigm in which ad lib. chow-fed rodents are trained to 'binge' on a high-fat diet (HFD) offered each day for a limited period of 2 hours. After 2 weeks of habituation to this paradigm, on the test day and immediately prior to the 2-hour PSF, rats were administered ghrelin or vehicle solution by the i.c.v. route. Remarkably and unexpectedly, during the palatable scheduled feed, when rats normally only binge on the HFD, those injected with i.c.v. ghrelin started to eat more chow and chow intake remained above baseline for the rest of the 24-hour day. We identify the ventral tegmental area (VTA) (a key brain area involved in food reward) as a substrate involved because these effects could be reproduced, in part, by intra-VTA delivery of ghrelin. Fasting, which increases endogenous ghrelin, immediately prior to a palatable schedule feed also increased chow intake during/after the schedule feed but, in contrast to ghrelin injection, did not reduce HFD intake. Chronic continuous central ghrelin infusion over several weeks enhanced binge-like behaviour in palatable schedule fed rats. Over a 4-week period, GHS-R1A-KO mice were able to adapt and maintain large meals of HFD in a manner similar to wild-type mice, suggesting that ghrelin signalling may not have a critical role in the acquisition or maintenance in this kind of feeding behaviour. In conclusion, ghrelin appears to act as a modulating factor for binge-like eating behaviour by shifting food preference towards a more nutritious choice (from HFD to chow), with these effects being somewhat divergent from fasting.

The core symptoms of bulimia nervosa, anxiety, and depression: A network analysis

Bulimia nervosa (BN) is characterized by symptoms of binge eating and compensatory behavior, and overevaluation of weight and shape, which often co-occur with symptoms of anxiety and depression. However, there is little research identifying which specific BN symptoms maintain BN psychopathology and how they are associated with symptoms of depression and anxiety. Network analyses represent an emerging method in psychopathology research to examine how symptoms interact and may become self-reinforcing. In the current study of adults with a Diagnostic and Statistical Manual for Mental Disorders-Fourth Edition (DSM-IV) diagnosis of BN (N = 196), we used network analysis to identify the central symptoms of BN, as well as symptoms that may bridge the association between BN symptoms and anxiety and depression symptoms. Results showed that fear of weight gain was central to BN psychopathology, whereas binge eating, purging, and restriction were less central in the symptom network. Symptoms related to sensitivity to physical sensations (e.g., changes in appetite, feeling dizzy, and wobbly) were identified as bridge symptoms between BN, and anxiety and depressive symptoms. We discuss our findings with respect to cognitive-behavioral treatment approaches for BN. These findings suggest that treatments for BN should focus on fear of weight gain, perhaps through exposure therapies. Further, interventions focusing on exposure to physical sensations may also address BN psychopathology, as well as co-occurring anxiety and depressive symptoms. (PsycINFO Database Record

Altered serum level of matrix metalloproteinase-9 and its association with decision-making in eating disorders

AIM

The aims of this study were to determine whether the serum levels of precursor brain-derived neurotrophic factor (proBDNF), mature BDNF (mBDNF), and matrix metalloproteinase-9 (MMP-9) are altered in patients with eating disorders (ED), including anorexia nervosa (AN) and bulimia nervosa (BN), and to explore whether those levels are associated with decision-making abilities.

METHODS

Nineteen women with AN, 28 women with BN, and 22 age-matched healthy control women (HC) were enrolled in the current study. All participants had their decision-making abilities assessed using the Iowa Gambling Task (IGT). Their eating-related pathophysiology and depressive/anxiety symptoms were also evaluated.

RESULTS

The MMP-9 level in AN was significantly lower than that in either BN or HC, but the serum levels of proBDNF and mBDNF did not differ among the three groups. Investigation of the serum levels of proBDNF and MMP-9 in patients with ED and controls revealed a significant correlation between them. In the BN, there were positive correlations between mBDNF level and IGT performance and also between MMP-9 level and IGT performance, but these correlations did not occur in AN. The MMP-9 level was positively associated with the Symptom Scale, one of the subscales of the Bulimic Investigatory Test, Edinburgh, only in AN.

CONCLUSION

These results suggest that the serum level of MMP-9 plays a role in the pathophysiology of AN, and both the serum levels of mBDNF and MMP-9 may be associated with decision-making abilities in patients with BN.

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.

OPRD1 Genetic Variation and Human Disease

The OPRD1 gene encodes the delta-opioid receptor, which has multiple functions including regulating reward pathways. The gene contains more than 2,000 verified genetic variants but only 2 currently have evidence for specific functions: rs1042114 disrupts maturation of the receptor and rs569356 affects OPRD1 expression. These polymorphisms and others in the gene have been found to be associated with human diseases. The most reproducible data are associations between opioid addiction and three variants in intron 1 (rs2236861, rs2236857, and rs3766951), which have been described in a number of independent populations. Several publications also point toward an association between anorexia and a haplotype block containing rs569356 and rs533123. Unfortunately the mechanisms underlying these two effects are currently unknown. In contrast, rs1042114 has been linked to Alzheimer's disease through an increasingly well-defined mechanism by which the variant allele reduces production of the beta-amyloid plaques associated with the disease. Additional studies of OPRD1 variants are necessary to replicate current findings and to delineate the functional roles of relevant polymorphisms.

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.

Examining the effect of binge eating and disinhibition on compensatory changes in energy balance following exercise among overweight and obese women

Some women behaviorally compensate for the energy expended during exercise by increasing their energy intake or becoming more sedentary, thereby decreasing their energy expenditure. Although behavioral compensation can attenuate or even reverse the energy deficit generated by exercise, few data are available on predictors of compensatory responses to exercise. The present study aimed to identify eating-related predictors of compensatory changes in energy balance following exercise. Overweight and obese, physically inactive women (N=48) completed self-report measures of disinhibition and binge eating and participated in two experimental conditions, exercise and rest, in counterbalanced order. Energy intake and expenditure were measured for 24-hours following each experimental condition to estimate energy balance. On average, women were 21.33±2.09years old and 63% were white. Of the sample, 63% compensated for the energy expended during exercise by increasing their energy intake or decreasing their energy expenditure. Linear mixed effects modeling with repeated measurement showed that disinhibition was not predictive of behavioral compensation. However, there was a significant difference between the negative energy balance observed following the rest condition and the positive energy balance observed following the exercise condition among women who reported binge eating, which was driven by a tendency to spend less time being physically active and more time being sedentary following exercise. These findings indicate that women who binge eat may be at greatest risk of compensating for exercise. Future research is needed to better understand psychosocial predictors and common mechanisms through which behavioral compensation is promoted.

The neurobiological basis of binge-eating disorder

Relatively little is known about the neuropathophysiology of binge-eating disorder (BED). Here, the evidence from neuroimaging, neurocognitive, genetics, and animal studies are reviewed to synthesize our current understanding of the pathophysiology of BED. Binge-eating disorder may be conceptualized as an impulsive/compulsive disorder, with altered reward sensitivity and food-related attentional biases. Neuroimaging studies suggest there are corticostriatal circuitry alterations in BED similar to those observed in substance abuse, including altered function of prefrontal, insular, and orbitofrontal cortices and the striatum. Human genetics and animal studies suggest that there are changes in neurotransmitter networks, including dopaminergic and opioidergic systems, associated with binge-eating behaviors. Overall, the current evidence suggests that BED may be related to maladaptation of the corticostriatal circuitry regulating motivation and impulse control similar to that found in other impulsive/compulsive disorders. Further studies are needed to understand the genetics of BED and how neurotransmitter activity and neurocircuitry function are altered in BED and how pharmacotherapies may influence these systems to reduce BED symptoms.

Behavioral and hormonal responses to stress in binge-like eating prone female rats

Binge eating episodes are frequently stimulated by stress. We developed a model of binge eating proneness based on individual sensitivity of young female Sprague Dawley rats to significantly increase sucrose consumption in response to stress. The rats were subjected to unpredictable intermittent 1-h access to 10% sucrose. After the stabilization of sucrose intake, rats were assessed for consistency of higher (for binge-like eating prone, BEP) or lower (for binge-like eating resistant, BER) sucrose intake in response to unpredictable episodes of foot-shock stress. The objectives of this study included demonstrating face validity of the BEP model and determining if some of the features of this model were pre-existing before exposure to intermittent access to sucrose and repeated stress. The BEP rats consumed a larger (20%>BER) amount of sucrose in a discrete (1-h) period of time compared to the BER phenotype in non-stressful conditions and significantly increased sucrose intake (50%>BER) under stress. Conversely, stress did not affect sucrose intake in BER rats. BEP rats showed higher sucrose intake compared to BER rats at the beginning of darkness as well as during the light period when they were sated and not physically hungry. Analyses of the sucrose licking microstructure revealed that BEP rats had a high motivational drive to consume sucrose in non-stressful condition and an increased hedonic value of sucrose when they were exposed to stressful conditions. BEP rats consumed sucrose much more rapidly under stressful conditions compared to BER rats. Finally, BEP rats demonstrated compulsive-like intake of sucrose (assessed in the light-dark box) and a blunted stress-induced increase in plasma corticosterone levels. Body weight and chow intake were not different between the phenotypes. Before exposure to intermittent access to sucrose and repeated stress, the BEP rats showed no clear evidence for compulsive sucrose intake. However, from the first 1-h access to sucrose, the BEP rats exhibited sucrose overeating; and from the first exposure to stress before intermittent access to sucrose, the BEP rats showed a blunted increase in corticosterone plasma levels. Innate sucrose hyperconsumption and altered reactivity of the hypothalamo-pituitary adrenal (HPA) axis to stress may be involved in the development of binge-like eating. Increased perceived hedonic value of palatable food and an increased motivation to consume this food despite aversive conditions as well as deregulated reactivity of the HPA axis may contribute to stress-induced bingeing on sucrose in BEP rats.

Role of relaxin-3/RXFP3 system in stress-induced binge-like eating in female rats

Binge eating is frequently stimulated by stress. The neuropeptide relaxin-3 (RLN3) and its native receptor RXFP3 are implicated in stress and appetitive behaviors. We investigated the dynamics of the central RLN3/RXFP3 system in a newly established model of stress-induced binge eating. Female Sprague-Dawley rats were subjected to unpredictable intermittent 1-h access to 10% sucrose. When sucrose intake stabilized, rats were assessed for consistency of higher or lower sucrose intake in response to three unpredictable episodes of foot-shock stress; and assigned as binge-like eating prone (BEP) or binge-like eating resistant (BER). BEP rats displayed elevated consumption of sucrose under non-stressful conditions (30% > BER) and an additional marked increase in sucrose intake (60% > BER) in response to stress. Conversely, sucrose intake in BER rats was unaltered by stress. Chow intake was similar in both phenotypes on 'non-stress' days, but was significantly reduced by stress in BER, but not BEP, rats. After stress, BEP, but not BER, rats displayed a significant increase in RLN3 mRNA levels in the nucleus incertus. In addition, in response to stress, BEP, but not BER, rats had increased RXFP3 mRNA levels in the paraventricular and supraoptic nuclei of the hypothalamus. Intracerebroventricular administration of a selective RXFP3 antagonist, R3(B1-22)R, blocked the stress-induced increase in sucrose intake in BEP rats and had no effect on sucrose intake in BER rats. These results provide important evidence for a role of the central RLN3/RXFP3 system in the regulation of stress-induced binge eating in rats, and have therapeutic implications for eating disorders.

Whole-person Integrative Eating: A Program for Treating Overeating, Overweight, and Obesity

The whole-person integrative eating (WPIE) model and program provides insights into the underlying causes of overeating as well as a comprehensive program for treating overeating, overweight, and obesity. A wide range of guidelines on food and eating from ancient food wisdom from Eastern healing systems, world religions, and cultural traditions, as well as Western nutritional science, were distilled into 6 principles: (1) eat fresh, whole foods; (2) eat with positive feelings; (3) eat with mindfulness; (4) eat with gratitude; (5) eat with loving regard; and (6) eat while dining with others. To assess how well individuals follow these guidelines, an 80-item questionnaire was developed and administered to a large sample of 5256 Americans who participated in a 6-wk, 18-lesson online e-course on integrative eating. Based on a factor analysis of the items, 7 distinct overeating styles emerged that are opposite of the perennial principles: (1) emotional eating, (2) fast foodism, (3) food fretting, (4) task snacking, (5) sensory disregard, (6) unappetizing atmosphere, and (7) solo dining. All were significantly and independently related to overeating frequency, and 5 of the 7 were significantly related to being overweight or obese. The case study presented here demonstrates how a 64-y-old woman who struggled with obesity throughout adolescence and adulthood was able to replace her 7 overeating styles with the 6 perennial integrative-eating guidelines for optimal eating. At the beginning of the year's coaching intervention, Barbara weighed 107 kg and wore a size 3×; 1 y later, she weighed approximately 75 kg and wears a medium, size 12. She has attributed her weight loss to the wholeness of the integrative-eating program she practices.