Altered brain correlates of response inhibition and error processing in females with obesity and sweet food addiction: A functional magnetic imaging study

Cognitive and motor impulsivity in the healthy brain, and implications for eating disorders and obesity: A coordinate-based meta-analysis and systematic review

Alterations in the impulse-control balance, and in its neural bases, have been reported in obesity and eating disorders (EDs). Neuroimaging studies suggest a role of fronto-parietal networks in impulsive behaviour, with evaluation and anticipatory processes additionally recruiting meso-limbic regions. However, whether distinct facets of cognitive and motor impulsivity involve common vs. specific neural correlates remains unclear. We addressed this issue through Activation Likelihood Estimation (ALE) meta-analyses of fMRI studies on delay discounting (DD) and go/no-go (GNG) tasks, alongside conjunction and subtraction analyses. We also performed systematic reviews of neuroimaging studies using the same tasks in individuals with obesity or EDs. ALE results showed consistent activations in the striatum, anterior/posterior cingulate cortex, medial/left superior frontal gyrus and left supramarginal gyrus for impulsive choices in DD, while GNG tasks elicited mainly right-lateralized fronto-parietal activations. Conjunction and subtraction analyses showed: i) common bilateral responses in the caudate nucleus; ii) DD-specific responses in the ventral striatum, anterior/posterior cingulate cortex, left supramarginal and medial frontal gyri; iii) GNG-specific activations in the right inferior parietal cortex. Altered fronto-lateral responses to both tasks are suggestive of dysfunctional cortico-striatal balance in obesity and EDs, but these findings are controversial due to the limited number of studies directly comparing patients and controls. Overall, we found evidence for distinctive neural correlates of the motor and cognitive facets of impulsivity: the right inferior parietal lobe underpins action inhibition, whereas fronto-striatal regions and the left supramarginal gyrus are related to impulsive decision-making. While showing that further research on clinical samples is required to better characterize the neural bases of their behavioural changes, these findings help refining neurocognitive model of impulsivity and highlight potential translational implications for EDs and obesity treatment.

Task fMRI studies investigating inhibitory control in patients with obsessive-compulsive disorder and eating disorders: A comparative meta-analysis

BACKGROUND

Obsessive-compulsive disorder (OCD) and eating disorders (EDs) share similarities in terms of clinical characteristics and deficits in inhibitory control.

OBJECTIVE

To investigate whether inhibitory control could serve as a common behavioural phenotype between OCD and EDs and whether it might be underpinned by shared and/or distinct neural signatures.

METHOD

We performed a quantitative meta-analysis of brain function abnormalities during the inhibitory control task-based functional Magnetic Resonance Imaging (fMRI) scan across patients with OCD and EDs using seed-based d mapping (SDM).

RESULTS

The meta-analysis included sixteen OCD fMRI studies and ten EDs fMRI studies. And findings revealed that patients with OCD showed hypoactivation relative to healthy controls and patients with EDs in the anterior cingulate cortex, while compared to healthy controls and patients with OCD, patients with EDs showed hypoactivation in the right insula.

CONCLUSIONS

Patients with OCD and EDs are inclined to exhibit impaired inhibitory control, which may be attributed to different abnormal patterns of neural activation.

Patient perceptions regarding alcohol use after bariatric surgery

INTRODUCTION

Patients who have undergone bariatric surgery are at increased risk of an alcohol use disorder. Though patients understand this risk, the majority engage in post-surgical alcohol use. This suggests that education alone is not sufficient to reduce post-surgical drinking. To prevent development of post-surgical alcohol use disorders, we need better understanding of the reasons patients use alcohol following surgery. The purpose of this study was to identify factors associated with post-surgical alcohol use.

METHOD

Patients (N = 20) who were 1-3 years post-bariatric surgery and were consuming alcohol at least twice monthly participated in a 60-min interview. Participants responded about their knowledge regarding risk of post-surgical alcohol use and reasons why patients may start drinking. Deductive and inductive coding were completed by two independent raters.

RESULTS

Although nearly all participants were aware of the risks associated with post-surgical alcohol use, most believed that lifelong abstinence from alcohol was unrealistic. Common reasons identified for using alcohol after bariatric surgery included social gatherings, resuming pre-surgical use, and addiction transfer. Inductive coding identified three themes: participants consumed alcohol in different ways compared to prior to surgery; the effect of alcohol was substantially stronger than pre-surgery; and beliefs about why patients develop problematic alcohol use following surgery.

CONCLUSION

Patients consume alcohol after bariatric surgery for a variety of reasons and they do not believe recommending abstinence is useful. Understanding patient perceptions can inform interventions to minimize alcohol use after bariatric surgery. Modifications to traditional alcohol relapse prevention strategies may provide a more robust solution to decreasing negative outcomes experienced by individuals undergoing bariatric surgery.

Brain functional and structural magnetic resonance imaging of obesity and weight loss interventions

Obesity has tripled over the past 40 years to become a major public health issue, as it is linked with increased mortality and elevated risk for various physical and neuropsychiatric illnesses. Accumulating evidence from neuroimaging studies suggests that obesity negatively affects brain function and structure, especially within fronto-mesolimbic circuitry. Obese individuals show abnormal neural responses to food cues, taste and smell, resting-state activity and functional connectivity, and cognitive tasks including decision-making, inhibitory-control, learning/memory, and attention. In addition, obesity is associated with altered cortical morphometry, a lowered gray/white matter volume, and impaired white matter integrity. Various interventions and treatments including bariatric surgery, the most effective treatment for obesity in clinical practice, as well as dietary, exercise, pharmacological, and neuromodulation interventions such as transcranial direct current stimulation, transcranial magnetic stimulation and neurofeedback have been employed and achieved promising outcomes. These interventions and treatments appear to normalize hyper- and hypoactivations of brain regions involved with reward processing, food-intake control, and cognitive function, and also promote recovery of brain structural abnormalities. This paper provides a comprehensive literature review of the recent neuroimaging advances on the underlying neural mechanisms of both obesity and interventions, in the hope of guiding development of novel and effective treatments.

Cerebral 18 F-fluorodeoxyglucose metabolism alteration of reward- and motivation-related regions in groups of different BMI classifications

OBJECTIVE

This study explored the relationship between BMI and regional cerebral glucose metabolism and explicitly detected regions with significant differences in cerebral metabolism using positron emission tomography (PET)/magnetic resonance imaging in the resting state.

METHODS

Corresponding PET images acquired from 220 participants were sorted into four groups according to Asian BMI standards: underweight, normal weight, overweight, and obesity. Pearson correlation coefficient analysis was performed to assess the association between BMI and standard uptake value. The regional cerebral glucose metabolism was measured in the fasted state. The PET images were analyzed using statistical parameter maps. One-way ANOVA was used to explore differences in the standard uptake value as an indicator of regional cerebral glucose metabolism.

RESULTS

This study found that lower cerebral glucose metabolism in reward- and motivation-related regions was accompanied by more severe obesity and that regional cerebral glucose metabolism activities were negatively correlated with BMI. In addition, more severe obesity was accompanied by a larger range of areas with significant differences independent of current dietary status.

CONCLUSIONS

These findings suggest that the reward and motivation circuits may be a factor regulating energy balance and influencing the degree of obesity.

Neural structural abnormalities behind altered brain activation in obesity: Evidence from meta-analyses of brain activation and morphometric data

Obesity represents a risk factor for disability with a major bearing on life expectancy. Neuroimaging techniques are contributing to clarify its neurobiological underpinnings. Here, we explored whether structural brain abnormalities might accompany altered brain activations in obesity. We combined and compared data from brain activation studies for food stimuli and the data reported in structural voxel-based morphometry studies. We found that obese individuals have reduced grey matter density and functional activations in the thalamus and midbrain. A functional connectivity analysis based on these two clusters and its quantitative decoding showed that these regions are part of the reward system functional brain network. Moreover, we found specific grey matter hypo-densities in prefrontal cortex for the obese subjects, regions involved in controlled behaviour. These results support theories of obesity that point to reduced bottom-up reward processes (i.e., the Reward Deficit Theory), but also top-down theories postulating a deficit in cognitive control (i.e., the Inhibitory Control Deficit Theory). The same results also warrant a more systematic exploration of obesity whereby the reward of food and the intentional control over consummatory behaviour is manipulated.

Examination of Individual Differences in Susceptibility to Food Addiction using Alcohol and Addiction Research Domain Criteria (AARDoC): Recent Findings and Directions for the Future

Purpose of Review

Alcohol and Addiction Research Domain Criteria (AARDoC) is a transdiagnostic, circuits-based framework for studying addictive behaviors. We examined parallels in individual differences that might increase susceptibility to FA and other addictive disorders using the following units of analysis in AARDoC domains: craving, relative reinforcing value of food and attention bias in the incentive salience domain; decisional impulsivity (delay discounting) and inhibitory control (Go-No-Go, Conner’s Continuous Performance Test, and the flanker task) in the executive function domain; and emotion dysregulation and negative urgency in the negative emotionality domain.

Recent Findings

There are a number of parallels between FA and other addictions in the incentive salience and negative emotionality domains, but somewhat divergent findings in the executive function domain. Trauma appears to be an important environmental stressor in maintenance of FA.

Summary

AARDoC may be a useful organizing framework for studying addictions, including FA. Future studies should incorporate other units of analysis to better characterize FA.

Food Addiction and Emotional Eating Behaviors Co-Occurring with Problematic Smartphone Use in Adolescents?

Addiction in adolescence is increasing and has a significant impact on physical and mental health. Notably, addictions can be comorbid and affect each other. Despite the recent growing interest in food addiction (FA) and problematic smartphone use (PSU), few studies have investigated their association in adolescents. We investigated the relationship between FA and PSU in adolescents and the effects of eating behaviors. A total of 209 adolescents (44.5% male; mean age = 12.86 ± 0.7 years) participated in the current school-based community study. We found a positive correlation between the dimensional Yale Food Addiction Scale for Children 2.0 (dYFAS-C2.0) and the Smartphone Overdependence Scale after adjusting for age, sex, body mass index, and socioeconomic status. The high-risk PSU group accounted for 17.2% of participants. Furthermore, this group showed 2.3 times higher dYFAS-C2.0 scores than the general group. Emotional overeating and satiety responsiveness were correlated with PSU. A comprehensive evaluation of addiction symptoms is needed for proper intervention, especially in adolescents with symptoms of abnormal eating behaviors.

Cognitive function in binge eating disorder and food addiction: A systematic review and three-level meta-analysis

BACKGROUND

An extensive body of recent research has focused on the contribution of cognitive functioning to eating behaviors. In binge eating disorder (BED) and food addiction (FA), the extent of cognitive impairment is still unclear. This study aimed to characterize, among those with BED and FA, neurocognitive functions using performances based on neuropsychological tasks in the context of neutral stimuli in adults.

METHOD

MEDLINE, Embase, PsycINFO, Cochrane Database of Systematic Reviews, CINAHL and gray literature (ProQuest and OpenGrey) were used to identify studies that reported neurocognitive assessments in BED or FA up to December 2019. A three-level meta-analysis was conducted.

RESULTS

A significant overall effect was found for global cognitive impairments, suggesting that individuals with BED or FA have poorer performances when completing cognitive tasks. Analyses for specific cognitive domains revealed that individuals with BED showed poorer performances at tasks assessing cognitive flexibility, inhibitory control, attention and planning. Analyses regarding FA were inconclusive due to a lack of studies. Thus, the results were described qualitatively.

CONCLUSION

Our meta-analysis highlighted the cognitive weaknesses that seem to come with BED and the necessity to integrate them in the assessment and treatment of this condition. It also stressed the lack of quality studies surrounding the cognitive features of FA.

Food addiction in a large community sample of Canadian adults: prevalence and relationship with obesity, body composition, quality of life and impulsivity

BACKGROUND AND AIMS

Parallels between the persistent overconsumption of food and addictive drugs have given rise to the notion of food addiction. In a large community sample of Canadian adults, the current study examined the prevalence of food addiction and its relationship with obesity, quality of life and multiple indicators of impulsivity. A secondary goal was to analyze differences between obese and non-obese individuals with and without food addiction.

DESIGN

Cross-sectional in-person assessment.

SETTING

Hamilton, Ontario, Canada.

PARTICIPANTS

A total of 1432 community adults (age = mean ± standard deviation = 38.93 ± 13.7; 42% male) recruited from the general community using print, bus and internet advertisements.

MEASUREMENTS

Yale Food Addiction Scale 2.0, anthropometrics (including body mass index), body composition (e.g. body fat, muscle mass, body water), World Health Organization Quality of Life scale and impulsivity measures, including impulsive personality traits, delay discounting and behavioral inhibition.

FINDINGS

The prevalence of food addiction was 9.3% and substantially below that of obesity (32.7%), although food addiction was significantly more common among obese individuals (18.5%, P < 0.001). Food addiction was associated with significantly lower quality of life in all domains (βs = -0.21 to -0.34, Ps < 0.001) and significantly higher impulsive personality traits, particularly negative and positive urgency (βs = 0.37 and 0.30, Ps < 0.001). Subgroup contrasts within both the obese and non-obese strata revealed that food addiction was associated with significantly lower quality of life in all domains (Ps < 0.001). Food addiction among non-obese individuals was also associated with higher body mass index (P < 0.001).

CONCLUSION

In a general community sample, food addiction was present in slightly fewer than one in 10 individuals, approximately one-third the prevalence of obesity, but with twice the prevalence among obese individuals. Food addiction appears to be associated with substantively lower quality of life and elevations in impulsivity, particularly in deficits in emotional regulation.

Event-related potential (ERP) measures of error processing as biomarkers of externalizing disorders: A narrative review

Previous studies have shown that electrophysiological measures of error processing are affected in patients at risk or diagnosed with internalizing disorders, hence, suggesting that error processing could be a suitable biomarker for internalizing disorders. In this narrative review, we will evaluate studies that address the role of event-related potential (ERP) measures of error-processing in externalizing disorders and discuss to what extend these can be considered a biomarker for externalizing disorders. Currently, there is evidence for the notion that electrophysiological indices of error processing such as the error-related negativity (ERN) and error positivity (Pe) are reduced in individuals with substance use disorders, attention-deficit/hyperactivity disorder, and in forensic populations. However, it remains unclear whether this is also the case for other understudied disorders such as behavioral addiction. Furthermore, to fully understand how these deficits affect day to day behavior, we encourage research to focus on testing current theories and hypotheses of ERN and Pe. In addition, we argue that within an externalizing disorder, individual differences in error processing deficits may be related to prognosis and gender of the patient, methodological issues and presence of comorbidity. Next, we review studies that have related treatment trajectories with ERP measures of error processing, and we discuss the prospect of improving error processing as a treatment option. We conclude that ERP measures of error processing are candidate biomarkers for externalizing disorders, albeit we strongly urge researchers to continue looking into the predictive value of these measures in the etiology and treatment outcome through multi-method and longitudinal designs.

A Systematic Review of Obesity and Binge Eating Associated Impairment of the Cognitive Inhibition System

Altered functioning of the inhibition system and the resulting higher impulsivity are known to play a major role in overeating. Considering the great impact of disinhibited eating behavior on obesity onset and maintenance, this systematic review of the literature aims at identifying to what extent the brain inhibitory networks are impaired in individuals with obesity. It also aims at examining whether the presence of binge eating disorder leads to similar although steeper neural deterioration. We identified 12 studies that specifically assessed impulsivity during neuroimaging. We found a significant alteration of neural circuits primarily involving the frontal and limbic regions. Functional activity results show BMI-dependent hypoactivity of frontal regions during cognitive inhibition and either increased or decreased patterns of activity in several other brain regions, according to their respective role in inhibition processes. The presence of binge eating disorder results in further aggravation of those neural alterations. Connectivity results mainly report strengthened connectivity patterns across frontal, parietal, and limbic networks. Neuroimaging studies suggest significant impairment of various neural circuits involved in inhibition processes in individuals with obesity. The elaboration of accurate therapeutic neurocognitive interventions, however, requires further investigations, for a deeper identification and understanding of obesity-related alterations of the inhibition brain system.

Improvement in Uncontrolled Eating Behavior after Laparoscopic Sleeve Gastrectomy Is Associated with Alterations in the Brain-Gut-Microbiome Axis in Obese Women

BACKGROUND

Bariatric surgery is proven to change eating behavior and cause sustained weight loss, yet the exact mechanisms underlying these changes are not clearly understood. We explore this in a novel way by examining how bariatric surgery affects the brain-gut-microbiome (BGM) axis.

METHODS

Patient demographics, serum, stool, eating behavior questionnaires, and brain magnetic resonance imaging (MRI) were collected before and 6 months after laparoscopic sleeve gastrectomy (LSG). Differences in eating behavior and brain morphology and resting-state functional connectivity in core reward regions were correlated with serum metabolite and 16S microbiome data.

RESULTS

LSG resulted in significant weight loss and improvement in maladaptive eating behaviors as measured by the Yale Food Addiction Scale (YFAS). Brain imaging showed a significant increase in brain volume of the putamen (p.adj < 0.05) and amygdala (p.adj < 0.05) after surgery. Resting-state connectivity between the precuneus and the putamen was significantly reduced after LSG (p.adj = 0.046). This change was associated with YFAS symptom count. Bacteroides, Ruminococcus, and Holdemanella were associated with reduced connectivity between these areas. Metabolomic profiles showed a positive correlation between this brain connection and a phosphatidylcholine metabolite.

CONCLUSION

Bariatric surgery modulates brain networks that affect eating behavior, potentially through effects on the gut microbiota and its metabolites.

Morphopathological changes in obsessive-compulsive disorder

The pathophysiology of the obsessive-compulsive disorder (OCD) has been studied for many years using several structural magnetic resonance imaging, discovering that the anomalies of function and structure of the brain are widespread, they involve different areas, structures and circuits with a complex interconnectivity. More than that, these anomalies cover all the life of a patient, from early childhood, due to variations of developmental stages until adult life. The research is highly important also because OCD has a major hereditary factor, with the phenotype variance between 27–47% due to hereditary factors. Under this paper, that follows last 10 years studies in this area, we will find some relevant findings consisting on neuroanatomic changes, the morphology findings of striatum, globus pallidus and thalamus, the blood flow circuit changes in various regions of the brain, brain connectivity and various correlations of them. Not to forget that OCD must be understand as an emotional disorder but in the same time as a cognitive disorder too. This approach highlights the abnormalities that have been found in brain regions involved in the cognitive and emotional behavior, as for example: extended temporal, parietal, and occipital regions, anterior cingulate, frontal gyrus, amygdala.

Functional connectivity within the salience network differentiates autogenous- from reactive-type obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is a clinically heterogeneous condition. To better understand and treat patients, symptomatology of OCD has been categorized into more homogenous symptom dimensions. The autogenous-reactive classification model has proven helpful in the elucidation of the neurobiological substrates for clinical heterogeneity in OCD. The purpose of the current study was to systematically compare regional and network functional alterations between OCD subtypes based on the autogenous-reactive model.

METHODS

Autogenous-type OCD patients (OCD-AO, n = 40), reactive-type patients (OCD-RO, n = 42), and healthy controls (HC, n = 70) underwent functional magnetic resonance imaging (fMRI) scans. The amplitude of low-frequency fluctuation (ALFF) and regional homogeneity (ReHo) were compared among subjects. Areas of abnormal local spontaneous brain activity that differentiated OCD-AO and OCD-RO patients were identified and entered as seeds in functional connectivity (FC) analysis.

RESULTS

Compared to OCD-RO patients and HC participants, OCD-AO patients showed increased ALFF in the left anterior insula (AI), increased ReHo in the right AI, and hyperconnectivity between bilateral AI and anterior cingulate cortex (ACC). Both OCD-AO and OCD-RO patients shared regional function deficits in several areas within the prefrontal cortex, and stronger FC between bilateral AI and major nodes of the default mode network (DMN) compared to healthy controls.

CONCLUSION

The current results suggest that aberrant functional interaction between the salience network (SN) and the DMN may represent a common substrate in the pathophysiology of OCD, while impaired functional coupling within the SN is distinct to autogenous-type OCD patients. These findings provide further neurobiological evidence to support the autogenous-reactive classification model and contribute to the understanding of the neurobiological basis for clinical heterogeneity in OCD.

Reward-related brain activity and behavior are associated with peripheral ghrelin levels in obesity

BACKGROUND/OBJECTIVES

While excessive food consumption represents a key factor in the development of obesity, the underlying mechanisms are still unclear. Ghrelin, a gut-brain hormone involved in the regulation of appetite, is impaired in obesity. In addition to its role in eating behavior, this hormone was shown to affect brain regions controlling reward, including the striatum and prefrontal cortex, and there is strong evidence of impaired reward processing in obesity. The present study investigated the possibility that disrupted reward-related brain activity in obesity relates to ghrelin deficiency.

SUBJECTS/METHODS

Fifteen severely obese subjects (BMI > 35 kg/m²) and fifteen healthy non-obese control subjects (BMI < 30 kg/m²) were recruited. A guessing-task paradigm, previously shown to activate the ventral striatum, was used to assess reward-related brain neural activity by functional magnetic resonance imaging (fMRI). Fasting blood samples were collected for the measurement of circulating ghrelin.

RESULTS

Significant activations in the ventral striatum, ventromedial prefrontal cortex and extrastriate visual cortex were elicited by the fMRI task in both obese and control subjects. In addition, greater reward-related activations were present in the dorsolateral prefrontal cortex, and precuneus/posterior cingulate of obese subjects compared to controls. Obese subjects exhibited longer choice times after repeated reward and lower circulating ghrelin levels than lean controls. Reduced ghrelin levels significantly predicted slower post-reward choices and reward-related hyperactivity in dorsolateral prefrontal cortices in obese subjects.

CONCLUSION

This study provides evidence of association between circulating ghrelin and reward-related brain activity in obesity and encourages further exploration of the role of ghrelin system in altered eating behavior in obesity.

Neural correlates of inhibitory control in youth with symptoms of food addiction

Prior research has found that food addiction is associated with reward-related neural differences, but research has yet to examine whether there are also neural differences in inhibitory control. This may be particularly relevant during adolescence as it is a key developmental period where difficulties in inhibitory control are more prevalent. The Yale Food Addiction Scale is a self-report questionnaire that applies substance use disorder diagnostic criteria to certain foods that has also been adapted for children. Here we investigate the association between addictive-like eating and brain functioning during inhibitory control in youth. Seventy-six right-handed participants 8.2-17.8 years (44 male) were recruited. Participants performed a go/no-go task during functional magnetic resonance imaging and completed the Yale Food Addiction Scale for Children, after which they were categorized into two groups according to their scores (No Symptom Group = 0; YFAS-C Group: score ≥ 1). Inhibitory control was probed with a contrast of correct no-go versus go trials. An independent-samples t-test comparing groups revealed a significant difference in three primary clusters, all exclusively in the left hemisphere (No Symptom Group > YFAS-C Group): middle temporal gyrus/occipital gyrus, precuneus/calcarine sulcus, and inferior frontal gyrus. Specifically, the YFAS-C Group showed deactivation in all three clusters. Adolescents who endorse food addiction appear to show hypo-activation in response to the inhibitory control portion of a go/no-go task, which suggests possible inhibitory control difficulties.

Fat Addiction: Psychological and Physiological Trajectory

Obesity has become a major public health concern worldwide due to its high social and economic burden, caused by its related comorbidities, impacting physical and mental health. Dietary fat is an important source of energy along with its rewarding and reinforcing properties. The nutritional recommendations for dietary fat vary from one country to another; however, the dietary reference intake (DRI) recommends not consuming more than 35% of total calories as fat. Food rich in fat is hyperpalatable, and is liable to be consumed in excess amounts. Food addiction as a concept has gained traction in recent years, as some aspects of addiction have been demonstrated for certain varieties of food. Fat addiction can be a diagnosable condition, which has similarities with the construct of addictive disorders, and is distinct from eating disorders or normal eating behaviors. Psychological vulnerabilities like attentional biases have been identified in individuals described to be having such addiction. Animal models have provided an opportunity to explore this concept in an experimental setting. This discussion sheds light on fat addiction, and explores its physiological and psychological implications. The discussion attempts to collate the emerging literature on addiction to fat rich diets as a prominent subset of food addiction. It aims at addressing the clinical relevance at the community level, the psychological correlates of such fat addiction, and the current physiological research directions.

Food addiction linked to changes in ventral striatum functional connectivity between fasting and satiety

INTRODUCTION

The concept of "food addiction" (FA) has gained popularity in view of clinical and neurobiological overlaps between excessive food intake and addictive disorders. However, no studies have examined the link between FA and striatocortical circuits involved in addictive disorders, or the influence of homeostatic status, which regulates the drive to eat, on these systems. This study aims to investigate changes in striatal functional connectivity between fasted and fed conditions among adults ranging in body mass index (BMI) and FA symptoms.

METHODS

Thirty adults were recruited from the general community and completed self-reported surveys including demographics, FA symptoms using the Yale Food Addiction Scale, as well as height and weight measures, used to determine BMI. Participants completed two 3-T MRI scans, one in a fasted state and one in a fed state. We conducted seed-based analyses to examine between-session ("fasted > fed") change in resting-state functional connectivity of the ventral and dorsal striatum, and its association with FA scores (controlling for BMI).

RESULTS

Higher symptoms of FA correlated with greater changes in ventral caudate-hippocampus connectivity between fasted and fed conditions. FA symptoms did not correlate with connectivity in the dorsal caudate circuit. Post-hoc analyses revealed that participants with higher symptoms of FA had ventral caudate-hippocampus hyperconnectivity in the fasted scan only, as well as a significant reduction of this connectivity between the fasted and fed scans.

CONCLUSIONS

Heightened connectivity in the ventral striatum during a fasted state, which has been linked to reward prediction signals, underpins symptoms of FA. In contrast, connectivity in the dorsal striatum or "habit" system is unrelated to homeostatic status and FA symptoms, and is thus less relevant for subclinical manifestations of FA.

Hungry brains: A meta-analytical review of brain activation imaging studies on food perception and appetite in obese individuals

The dysregulation of food intake in chronic obesity has been explained by different theories. To assess their explanatory power, we meta-analyzed 22 brain-activation imaging studies. We found that obese individuals exhibit hyper-responsivity of the brain regions involved in taste and reward for food-related stimuli. Consistent with a Reward Surfeit Hypothesis, obese individuals exhibit a ventral striatum hyper-responsivity in response to pure tastes, particularly when fasting. Furthermore, we found that obese subjects display more frequent ventral striatal activation for visual food cues when satiated: this continued processing within the reward system, together with the aforementioned evidence, is compatible with the Incentive Sensitization Theory. On the other hand, we did not find univocal evidence in favor of a Reward Deficit Hypothesis nor for a systematic deficit of inhibitory cognitive control. We conclude that the available brain activation data on the dysregulated food intake and food-related behavior in chronic obesity can be best framed within an Incentive Sensitization Theory. Implications of these findings for a brain-based therapy of obesity are briefly discussed.

Decision Making Deficits in Relation to Food Cues Influence Obesity: A Triadic Neural Model of Problematic Eating

In this review article we propose a model of the brain systems, the deficiency of which may underlie problematic eating. This integrative model is based on studies that have focused on discrete brain components involved in problematic eating, combined with insights from studies on the neurocognitive basis of other addictive and problematic behaviors. The model includes: (a) a hyper-functioning reward anticipation and processing system (amygdala-striatum dependent) in response to food-related cues; (b) a hypo-functioning reflective and inhibitory control system (prefrontal cortex dependent), that fails to anticipate and properly weigh future outcomes; and (c) an altered interoceptive awareness system (insular cortex dependent) that translates homeostatic violation signals into a strong consumption desire that hijacks the inhibitory system and excites the reward system. We posit that when the abovementioned systems are imbalanced in such a way that the dopamine axis is hyperactive in relation to food cues and the inhibitory system is weak, and this is further aggravated by an altered interoceptive awareness system, people may experience loss of control or inability to resist tempting/rewarding foods. This loss of control over food consumption can explain, at least in part, the development of excess weight and contribute to the obesity epidemic.

Food-Related Impulsivity in Obesity and Binge Eating Disorder-A Systematic Update of the Evidence

The specific eating pattern of Binge Eating Disorder (BED) patients has provoked the assumption that BED might represent a phenotype within the obesity spectrum that is characterized by increased impulsivity. Following the guidelines of the PRISMA statement (preferred reporting items for systematic reviews and meta-analyses), we here provide a systematic update on the evidence on food-related impulsivity in obese individuals, with and without BED, as well as normal-weight individuals. We separately analyzed potential group differences in the impulsivity components of reward sensitivity and rash-spontaneous behavior. Our search resulted in twenty experimental studies with high methodological quality. The synthesis of the latest evidence consolidates conclusions drawn in our initial systematic review that BED represents a distinct phenotype within the obesity spectrum that is characterized by increased impulsivity. Rash-spontaneous behavior in general, and specifically towards food, is increased in BED, while food-specific reward sensitivity is also increased in obese individuals without BED, but potentially to a lesser degree. A major next step for research entails the investigation of sub-domains and temporal components of inhibitory control in BED and obesity. Based on the evidence of impaired inhibitory control in BED, affected patients might profit from interventions that address impulsive behavior.