The role of reward circuitry and food addiction in the obesity epidemic: An update

5-Methoxy-2-aminoindane Reverses Diet-Induced Obesity and Improves Metabolic Parameters in Mice: A Potential New Class of Antiobesity Therapeutics

The escalating prevalence of obesity and its related disorders represents a daunting global health challenge. Unfortunately, current pharmacological interventions for obesity remain limited and are often associated with debilitating side effects. Against this backdrop, the psychoactive aminoindane derivative 5-methoxy-2-aminoindane (MEAI) has gained considerable attention for its ability to induce a pleasurable, alcohol-like sensation while curbing alcohol consumption. Given the potential impact of MEAI on food addiction and energy homeostasis, we examined its metabolic efficacy on appetite regulation, obesity, and related comorbidities under acute and chronic settings, utilizing a mouse model of diet-induced obesity (DIO). Our results demonstrated that MEAI treatment significantly reduced DIO-induced overweight and adiposity by preserving lean mass and decreasing fat mass. Additionally, MEAI treatment exhibited positive effects on glycemic control by attenuating DIO-induced hyperglycemia, glucose intolerance, and hyperinsulinemia. Furthermore, MEAI reduced DIO-induced hepatic steatosis by decreasing hepatic lipid accumulation and lowering liver triglyceride and cholesterol levels, primarily by inhibiting de novo lipid synthesis. Metabolic phenotyping revealed that MEAI increased energy expenditure and fat utilization while maintaining food consumption similar to that of the vehicle-treated group. Lastly, MEAI normalized voluntary locomotion actions without any overstimulatory effects. These findings provide compelling evidence for the antiobesity effects of MEAI treatment and call for further preclinical testing. In conclusion, our study highlights the potential of MEAI as a novel therapeutic approach for treating obesity and its associated metabolic disorders, offering hope for the development of new treatment options for this global health challenge.

Dietary intake in children and adolescents with food addiction: A systematic review

Food addiction (FA) is characterized by behavioral changes related to the consumption of palatable foods, marked by dependence, impulsivity, and compulsion. Children and adolescents are more vulnerable to FA owing to their significant consumption of ultra-processed foods. This review aims to investigate the differences in dietary intake in pediatric populations with and without FA. We conducted a systematic literature review. PubMed, ScienceDirect, and PsycINFO databases were searched up to July 2023. Potentially eligible studies were independently checked by two researchers. The methodological quality of the included studies was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for analytical cross-sectional studies. Of the 4868 articles identified, six studies were included. All the included studies had high methodological quality. High consumption of calories and fat was observed in children and adolescents with FA. A diet quality analysis showed that the consumption of ultra-processed foods, such as sugary drinks, sweets, and chips, was related to FA. Given these findings, we concluded that FA in childhood may be associated with higher energy consumption and, consequently, higher intake of macronutrients. Few studies have examined the relationship between FA and food intake in childhood, and more studies are required.

Social isolation postweaning alters reward-related dopamine dynamics in a region-specific manner in adolescent male rats

Early development is characterized by dynamic transitions in brain maturation, which may be impacted by environmental factors. Here, we sought to determine the effects of social isolation from postweaning and during adolescence on reward behavior and dopaminergic signaling in male rats. Subjects were socially isolated or group housed at postnatal day 21. Three weeks later, extracellular dopamine concentrations were examined in the medial prefrontal cortex (mPFC) and nucleus accumbens shell (NAc) during a feeding bout. Surprisingly, opposing effects were found in which increased mPFC dopamine concentrations were observed in group housed, but not isolated, rats. In stark contrast, increased dopamine levels were found in the NAc of isolated, but not group housed, rats. Moreover, the absence of an effect in the mPFC of the isolated rats could not be reversed by subsequent group housing, demonstrating the remarkable long-term effects on dopamine signaling dynamics. When provided a highly palatable food, the isolated subjects exhibited a dramatic increase in mPFC dopamine levels when the chocolate was novel, but no effects following chronic chocolate consumption. In contrast, the group housed subjects showed significantly increased dopamine levels only with chronic chocolate consumption. The dopamine changes were correlated with differences in behavioral measures. Importantly, the deficit in reward-related behavior during isolation could be reversed by microinjection of either dopamine or cocaine into the mPFC. Together, these data provide evidence that social isolation from postweaning and during adolescence alters reward-induced dopamine levels in a brain region-specific manner, which has important functional implications for reward-related behavior.

Mendelian Randomization Analysis Identifies Inverse Causal Relationship between External Eating and Metabolic Phenotypes

Disordered eating contributes to weight gain, obesity, and type 2 diabetes (T2D), but the precise mechanisms underlying the development of different eating patterns and connecting them to specific metabolic phenotypes remain unclear. We aimed to identify genetic variants linked to eating behaviour and investigate its causal relationships with metabolic traits using Mendelian randomization (MR). We tested associations between 30 genetic variants and eating patterns in individuals with T2D from the Volga-Ural region and investigated causal relationships between variants associated with eating patterns and various metabolic and anthropometric traits using data from the Volga-Ural population and large international consortia. We detected associations between HTR1D and CDKAL1 and external eating; between HTR2A and emotional eating; between HTR2A, NPY2R, HTR1F, HTR3A, HTR2C, CXCR2, and T2D. Further analyses in a separate group revealed significant associations between metabolic syndrome (MetS) and the loci in CRP, ADCY3, GHRL, CDKAL1, BDNF, CHRM4, CHRM1, HTR3A, and AKT1 genes. MR results demonstrated an inverse causal relationship between external eating and glycated haemoglobin levels in the Volga-Ural sample. External eating influenced anthropometric traits such as body mass index, height, hip circumference, waist circumference, and weight in GWAS cohorts. Our findings suggest that eating patterns impact both anthropometric and metabolic traits.

Long-term regulation of fat sensing in rainbow trout (Oncorhynchus mykiss) fed a vegetable diet from the first feeding: focus on free fatty acid receptors and their signalling

Taste plays a fundamental role in an animal’s ability to detect nutrients and transmits key dietary information to the brain, which is crucial for its growth and survival. Providing alternative terrestrial ingredients early in feeding influences the growth of rainbow trout (RT, Oncorhynchus mykiss). Thus, the present study aimed to assess the influence, via long-term feeding (from the first feeding to 8 months), of alternative plant ingredients (V diet for vegetable diet v. C diet for a control diet) in RT on the mechanism of fat sensing at the gustatory level. After the feeding trial, we studied the pathways of the fat-sensing mechanism in tongue tissue and the integrated response in the brain. To this end, we analysed the expression pattern of free fatty acid receptors (ffar) 1 and 2, markers of calcium-signalling pathways (phospholipase Cβ, Orai, Stim or Serca), the serotonin level (a key neurotransmitter in taste buds) and the expression pattern of appetite-regulating neuropeptides in the hypothalamus (central area of appetite regulation). The results revealed that the V diet modified the expression pattern of ffar1 and paralogs of ffar2 genes in tongue tissue, along with differential regulation of calcium-signalling pathways and a defect in serotonin level and brain turnover, without influencing neuropeptide expression. This study is the first to support that changes in feeding behaviour of RT fed a V diet could be due to the difference in nutrient sensing and a decrease in hedonic sensation. We revealed that RT have similar fat-detection mechanisms as mammals.

Food Addiction and Binge Eating Disorder in Relation to Dietary Patterns and Anthropometric Measurements: A Descriptive-Analytic Cross-Sectional Study in Iranian Adults with Obesity

Obesity is associated with maladaptive eating behaviors, including food addiction (FA) and binge eating disorder (BED). However, the key factors influencing the development of maladaptive eating behaviors remain unknown. Adherence to specified dietary patterns has been suspected of making indirect impacts. This study investigates the association of FA and BED with dietary patterns and anthropometric measurements among 400 Iranian adults (aged 18-60; 66.25% women) living with obesity (body mass index [BMI] ≥ 30 kg/m2). The Binge Eating Scale and Yale Food Addiction Scale were used to measure BED and FA. A validated 147-item semi-quantitative food frequency questionnaire underwent principal component analysis and identified three major dietary patterns: mixed, unhealthy, and healthy dietary pattern. After adjusting for confounders, higher adherence to unhealthy dietary patterns was associated with an increased risk of FA, while higher adherence to healthy dietary patterns was associated with a lower risk of FA. Also, those within obesity class III had a significantly higher risk of FA and BED than those in obesity class I. This study suggests that adherence to an unhealthy dietary pattern may be associated with a higher risk of FA. It also highlights the link between higher BMI and maladaptive eating behaviors.

Food addiction as a mediator between depressive symptom severity and body mass index

Depression is associated with an increased risk of cardiometabolic disease linked to weight gain driven by complex interactions between multiple risk factors, including overeating behaviours. However, risk factors that mediate the relationship between depressive symptoms and weight gain remain to be fully elucidated. This study examined food addiction symptoms as a potential mediator on the relationship between depressive symptom severity and adiposity as measured by body mass index (BMI), and evaluated whether this relationship was contingent on appetite symptom profile and sex. In a sample of 628 adults, depressive symptom severity was assessed using the Centre for Epidemiological Studies Depression Scale (CES-D), and food addiction symptoms were measured using the Yale Food Addiction Scale (YFAS, version 2). Participant demographics, including BMI, appetite presentations and sex, were assessed using self-report questions. Mediation and moderated mediation analyses were performed to determine relationships between variables. The prevalence of depressogenic food addiction in the present sample was 21.7%. After accounting for age and averaged amount of exercise, food addiction symptoms fully mediated the relationship between depressive symptom severity and BMI. Appetite symptom profile was a significant moderator of this relationship, with effects more pronounced in those with increased appetite compared to decreased or unchanged appetite. While sex was not a significant moderator, being male or female was associated with higher food addiction scores. This study supports food addiction symptoms as an important behavioural risk factor for increased adiposity linked to greater depressive symptom severity, particularly in those experiencing increased appetite during a depressive episode. Assessment and monitoring of food addiction symptoms may have utility in reducing the risk of increased BMI and adverse health outcomes in those experiencing more severe depressive symptoms.

Psychopathological factors and personality dimensions on dysfunctional eating behaviors in a sample of individuals with obesity

Introduction

Obesity and eating disorders are considered to be part of a broad spectrum of disorders associated with weight issues and maladaptive eating styles. Several studies show that psychopathological and personality characteristics contribute to the development and maintenance of obesity and dysfunctional eating behaviors, showing a bidirectional relationship. The purpose of this study was to understand the role of psychopathological factors and personality dimensions on dysfunctional eating behaviors in a sample of individuals with obesity.

Methods

The study was conducted with 96 individuals with obesity (31 males and 65 females) who underwent psychological assessment. The instruments administered included the Cognitive Behavioral Assessment 2.0 - Primary Scales, the Minnesota Multiphasic Personality Inventory-2, and the Eating Disorder Inventory. Relationships between dysfunctional eating behaviors and personality and psychopathological factors were explored through mediation analysis.

Results and discussion

Our results showed that difficulties related to impulse control and behavior, along with negative and dysphoric emotions, may be associated with difficulties in eating behavior. Mediation analysis showed that the combination of depressive and obsessive-compulsive symptomatology may exacerbate or contribute to the occurrence of eating disorders. These psychopathological aspects should be taken into account during the assessment of patients who decide to undergo bariatric surgery and should be targets of specific psychological interventions.

Disentangling the role of NAc D1 and D2 cells in hedonic eating

Overeating is driven by both the hedonic component ('liking') of food, and the motivation ('wanting') to eat it. The nucleus accumbens (NAc) is a key brain center implicated in these processes, but how distinct NAc cell populations encode 'liking' and 'wanting' to shape overconsumption remains unclear. Here, we probed the roles of NAc D1 and D2 cells in these processes using cell-specific recording and optogenetic manipulation in diverse behavioral paradigms that disentangle reward traits of 'liking' and 'wanting' related to food choice and overeating in healthy mice. Medial NAc shell D2 cells encoded experience-dependent development of 'liking', while D1 cells encoded innate 'liking' during the first food taste. Optogenetic control confirmed causal links of D1 and D2 cells to these aspects of 'liking'. In relation to 'wanting', D1 and D2 cells encoded and promoted distinct aspects of food approach: D1 cells interpreted food cues while D2 cells also sustained food-visit-length that facilitates consumption. Finally, at the level of food choice, D1, but not D2, cell activity was sufficient to switch food preference, programming subsequent long-lasting overconsumption. By revealing complementary roles of D1 and D2 cells in consumption, these findings assign neural bases to 'liking' and 'wanting' in a unifying framework of D1 and D2 cell activity.

Higher body weight-dependent neural activation during reward processing

Obesity is associated with alterations in brain structure and function, particularly in areas related to reward processing. Although brain structural investigations have demonstrated a continuous association between higher body weight and reduced gray matter in well-powered samples, functional neuroimaging studies have typically only contrasted individuals from the normal weight and obese body mass index (BMI) ranges with modest sample sizes. It remains unclear, whether the commonly found hyperresponsiveness of the reward circuit can (a) be replicated in well-powered studies and (b) be found as a function of higher body weight even below the threshold of clinical obesity. 383 adults across the weight spectrum underwent functional magnetic resonance imaging during a common card-guessing paradigm simulating monetary reward. Multiple regression was used to investigate the association of BMI and neural activation in the reward circuit. In addition, a one-way ANOVA model comparing three weight groups (normal weight, overweight, obese) was calculated. Higher BMI was associated with higher reward response in the bilateral insula. This association could no longer be found when participants with obesity were excluded from the analysis. The ANOVA revealed higher activation in obese vs. lean, but no difference between lean and overweight participants. The overactivation of reward-related brain areas in obesity is a consistent finding that can be replicated in large samples. In contrast to brain structural aberrations associated with higher body weight, the neurofunctional underpinnings of reward processing in the insula appear to be more pronounced in the higher body weight range.

[Physical growth and dietary characteristics of children with attention deficit hyperactivity disorder: a cross-sectional study]

OBJECTIVES

To investigate the physical growth and dietary characteristics of children with attention deficit hyperactivity disorder (ADHD), and to analyze their relationship with core symptoms of ADHD.

METHODS

A total of 268 children who were newly diagnosed with ADHD in Children's Hospital of Nanjing Medical University from June to December 2020 were included in the ADHD group, and 102 healthy children who underwent physical examination during the same period were selected as the control group. Physical evaluations and dietary surveys were conducted for both groups. ADHD diagnosis and scoring were performed according to the Diagnostic and Statistical Manual of Mental Disorders (5th edition). Factor analysis, Spearman correlation analysis, and mediation analysis were used to study the relationship between core symptoms of ADHD, dietary patterns, and physical growth.

RESULTS

The rate of overweight/obesity in the ADHD group was significantly higher than that in the control group (35.8% vs 21.6%, P<0.05). Three dietary patterns were extracted from the food frequency questionnaire: vegetarian dietary pattern, traditional dietary pattern, and snack/fast food pattern. The factor score for the snack/fast food pattern in the ADHD group was higher than that in the control group (P<0.05). There was a significant positive correlation between ADHD symptom scores, snack/fast food pattern factor scores, and body fat percentage (P<0.05). The mediation analysis showed that the snack/fast food pattern played a partial mediating role in the relationship between ADHD symptom scores and body fat percentage, with a mediation proportion of 26.66%.

CONCLUSIONS

The rate of overweight/obesity in children with ADHD is higher than that in non-ADHD children. Core symptoms of ADHD are related to dietary patterns and physical growth, with the snack/fast food pattern playing a partial mediating role in the relationship between core symptoms of ADHD and physical growth.

Pharmacological strategies for appetite modulation in eating disorders: a narrative review

BACKGROUND

A substantial increase in the prevalence of eating disorders has been noticed over the past decades. Priority in the treatment of eating disorders is justifiably given to psychosocial interventions. However, it is also well known that centrally acting drugs can significantly affect appetite and food consumption.

AIM

To narratively review the available neurobiological data on the mechanisms of central regulation of eating behavior as a rationale to summarize pharmacological strategies for appetite modulation in eating disorders.

METHODS

The authors have carried out a narrative review of scientific papers published from January 2013 to March 2023 in the PubMed and Web of Science electronic databases. Studies were considered eligible if they included data on the neurobiological mechanisms of appetite regulation or the results of clinical trials of centrally acting drugs in eating disorders. Relevant studies were included regardless of their design. Descriptive analysis was used to summarize the obtained data.

RESULTS

The review included 51 studies. The available neurobiological and clinical data allowed us to identify the following pharmacological strategies for appetite modulation in eating disorders: serotonergic, catecholaminergic, amino acidergic and peptidergic. However, implementation of these data into clinical practice difficult due to an insufficient number of good-quality studies, which is particularly relevant for adolescents as there is a research gap in this population.

CONCLUSION

The progress in neurobiological understanding of the mechanisms of central regulation of appetite opens opportunities for new pharmacotherapeutic approaches aimed at changing the patterns of eating behavior. Obviously, treatment of eating disorders is a much broader problem and cannot be reduced to the correction of eating patterns. Nevertheless, at certain stages of treatment, drug-induced modulation of appetite can play an important role among multi-targeted biological and psychosocial interventions. Translation of neurobiological data into clinical practice requires a large number of clinical studies to confirm the long-term efficacy and safety of pharmacotherapeutic approaches and to develop personalized algorithms for the treatment of various forms of eating disorders in different age groups.

Neural oscillations in the ventral striatum reveal differences between the encoding of palatable food and ethanol consumption

BACKGROUND

Across multiple levels of investigation, there appear to be convergent neuronal processes underlying substance use and other motivated behaviors (i.e., the pursuit and consumption of rewarding substances). The consumption of alcohol and sweet, high-fat food engages many of the same brain regions, especially, the ventral striatum. In the current study, we hypothesized that ventral striatal local field potentials (LFPs) recorded during self-administration sessions could be used to detect when the consumption of 10% ethanol or sweet-fat food (SF) was occurring compared to all other behaviors, including naturalistic controls (i.e., water or house-chow).

METHODS

We used an intermittent limited access approach to condition Sprague-Dawley rats to consume either ethanol or SF while we recorded LFPs. We used machine learning and simple logistic regressions to determine whether LFP features could classify when consumption of each substance was occurring, and whether a general model could predict consumption of both substances. We report performance as the average area under the receiver operator characteristic curve (AUROC).

RESULTS

Consumption of a single substance was differentiable from all other behaviors, as evidenced by the AUROC (ethanol = 0.84 and SF = 0.83, p < 0.01). Models built from the combined dataset (general) did modestly overall (general → general = 0.68, p < 0.05), and did not detect the consumption of the two substances similarly (general → SF = 0.5 and general → ethanol = 0.63, p > 0.05).

CONCLUSIONS

Models successfully classified ethanol and SF consumption versus all other behavior/naturalistic controls. However, the findings highlight differences in how the ventral striatum represents the consumption of ethanol and SF and show that, although there is potential for finding biomarkers related to substance use, it may be difficult to build a model that performs well detecting multiple substances.

Current Insights into the Potential Role of fMRI in Discovering the Mechanisms Underlying Obesity

Obesity is becoming one of the major global health concerns. This chronic disease affects around 650 million people worldwide and is an underlying cause of a number of significant comorbidities. According to the World Health Organization (WHO) report on obesity from 2022, this disorder became the fourth leading cause of deaths in Europe. Thus, understanding the mechanisms underlying obesity is of essential importance to successfully prevent and treat this disease. The aim of this study was to review the current insights into the potential role of fMRI in discovering the mechanisms underlying obesity on the basis of recent scientific literature published up to December 2022 and searches of the PubMed, Google Scholar and Web of Science databases. The literature assessed indicated that a growing body of evidence suggests that obesity leads to changes in both structure and connectivity within the central nervous system. Emerging data from recent functional magnetic resonance imaging (fMRI) studies prove that obese individuals present an increased motivational drive to eat as well as impaired processing in reward- and control-related brain regions. Apart from this, it is clear that fMRI might be a useful tool in detection of obesity-induced changes within the central nervous system.

The Effects of Obesity on the Inflammatory, Cardiovascular, and Neurobiological Responses to Exercise in Older Adults

Obesity with advancing age leads to increased health complications that are involved in various complex physiological processes. For example, inflammation is a critical cardiovascular disease risk factor that plays a role in the stages of atherosclerosis in both aging and obesity. Obesity can also induce profound changes to the neural circuitry that regulates food intake and energy homeostasis with advancing age. Here we discuss how obesity in older adults impacts inflammatory, cardiovascular, and neurobiological functions with an emphasis on how exercise mediates each topic. Although obesity is a reversible disorder through lifestyle changes, it is important to note that early interventions are crucial to prevent pathological changes seen in the aging obese population. Lifestyle modifications such as physical activity (including aerobic and resistance training) should be considered as a main intervention to minimize the synergistic effect of obesity on age-related conditions, such as cerebrovascular disease.

Metabolic Hormone Action in the VTA: Reward-Directed Behavior and Mechanistic Insights

Dysfunctional signaling in midbrain reward circuits perpetuates diseases characterized by compulsive overconsumption of rewarding substances such as substance abuse, binge eating disorder, and obesity. Ventral tegmental area (VTA) dopaminergic activity serves as an index for how rewarding stimuli are perceived and triggers behaviors necessary to obtain future rewards. The evolutionary linking of reward with seeking and consuming palatable foods ensured an organism's survival, and hormone systems that regulate appetite concomitantly developed to regulate motivated behaviors. Today, these same mechanisms serve to regulate reward-directed behavior around food, drugs, alcohol, and social interactions. Understanding how hormonal regulation of VTA dopaminergic output alters motivated behaviors is essential to leveraging therapeutics that target these hormone systems to treat addiction and disordered eating. This review will outline our current understanding of the mechanisms underlying VTA action of the metabolic hormones ghrelin, glucagon-like peptide-1, amylin, leptin, and insulin to regulate behavior around food and drugs of abuse, highlighting commonalities and differences in how these five hormones ultimately modulate VTA dopamine signaling.

Altered anticipatory brain responses in eating disorders: A neuroimaging meta-analysis

OBJECTIVE

Functional neuroimaging studies have found differential neural activation patterns during anticipation-related paradigms in participants with eating disorders (EDs) compared to controls. However, publications reported conflicting results on the directionality and location of the abnormal activations. There is an urgent need to integrate our existing knowledge of anticipation, both rewarding and aversive, to elucidate these differences.

METHOD

We conducted an activation likelihood estimation (ALE) meta-analysis to quantitatively review functional neuroimaging studies that evaluated differences between brain correlates of anticipation in participants with and without disordered eating. PubMed, Web of Sciences, PsycINFO, Medline and EMBASE were searched for studies published up to November 2022. Exploratory sub-analyses to check for differences between reward and non-reward anticipation among all anticipation paradigms.

RESULTS

Twenty-one references met the inclusion criteria for meta-analysis. The meta-analysis across anticipation all tasks identified a significant hyperactivation cluster in the right putamen in participants with disordered eating (n = 17 experiments) and a significant hypoactivation cluster in the left inferior parietal lobule (n = 13 experiments), in participants with disordered eating compared to controls.

CONCLUSIONS

These findings and sub-analyses of reward- and non-reward-related cues suggest potential pathophysiological mechanisms underlying anticipatory responses to rewarding and aversive cues in ED.

Associations among SNPs in two addictive genes, food addiction, and antioxidant markers in recreationally active young women

INTRODUCTION

food addiction is associated with genetic polymorphisms and decreased antioxidant intake.

OBJECTIVES

this study determined the associations among food addiction, dopamine receptor 2 (DRD2) and toll-interleukin 1 receptor (TIR) domain-containing adaptor protein (TIRAP rs625413) gene polymorphisms, antioxidant capacities, and zinc levels among recreationally active Turkish women.

METHODS

the Yale Food Addiction Scale was used to evaluate the food addiction status. Serum antioxidant capacities and zinc levels were evaluated by blood analyses. Deoxyribonucleic acid (DNA) extraction was performed using peripheral blood leukocytes, and the polymorphism status of the DRD2 Taq 1A and TIRAP genes was investigated using a commercial kit.

RESULTS

the frequencies of the heterozygous genotypes of DRD2 Taq 1A and TIRAP were 23.1 % and 31.4 %, respectively, and the frequency of risk allele homozygous genotypes was 3.2 %. Most participants (94.4 %) had a nonpolymorphic/wild (CC) genotype in both genes; however, 11.5 % of the participants had a food addiction. The differences between serum antioxidant capacities, zinc levels, and body mass indices of those with and without food addiction were statistically significant. However, there were no differences in the serum zinc and antioxidant levels among the different genotypes.

CONCLUSION

food addiction in young Turkish women was not associated with DRD2 Taq 1A or TIRAP polymorphisms but was associated with serum antioxidant capacities and zinc levels. Further studies on different loci of the same genes or genotypes of different genes with larger sample sizes are warranted.

Eating behavior-mediated association between attention deficit hyperactivity disorder and body fat mass

Background

Adverse eating behaviors and a high rate of obesity have been identified among children diagnosed with attention deficit hyperactivity disorder (ADHD). In this study, we investigate the relationships between eating behaviors and body fat mass among children with ADHD.

Methods

All participants were recruited from the Children's Health Care Department of the Children's Hospital of Nanjing Medical University from June 2019 to June 2020. ADHD was diagnosed according to the diagnostic criteria of the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) by psychiatrists. Core ADHD symptoms defined by the DSM-5 were inattention and hyperactivity/impulsivity. The anthropomorphic indices defined by the World Health Organization (WHO) were utilized in this study (body mass index [BMI], underweight, normal body mass, overweight, obesity, short stature). Body fat mass, fat mass percentage (FM%), skeletal muscle mass, skeletal muscle mass percentage (SMM%) were tested via body composition meter, and eating behaviors were assessed by parents using the Chinese version of the Children's Eating Behavior Questionnaire (CEBQ). The CEBQ was comprised of subscales related to food avoidant behaviors (satiety responsiveness, slowness in eating, fussiness, and emotional undereating) and food approach behaviors (food responsiveness, enjoyment of Food, desire to drink, and emotional overeating). The associations among ADHD, obesity and adverse eating behavior were tested through correlation analysis, and a mediating effect model was established to explore the effect of eating behaviors.

Results

A total of 548 participants aged 4-12 years were recruited. Among them, 396 were diagnosed with ADHD, with the remaining 152 enrolled in a control group. Compared with the control group, the ADHD group had higher incidences of overweight (22.5% vs. 14.5%) and obesity (13.4% vs. 8.6%) (p < 0.05). The ADHD group was more likely to display "slowness in eating" (11.01 ± 3.32 vs. 9.74 ± 2.95), "fussiness" (15.61 ± 3.54 vs. 15.03 ± 2.84), "food responsiveness" (11.96 ± 4.81 vs. 9.88 ± 3.71) and "desire to drink" (8.34 ± 3.46 vs. 6.58 ± 2.72) (p < 0.05). Moreover, The FM% of children with ADHD was positively correlated with inattention (β = 0.336, 95% CI: 0.001 to 0.673) and "food responsiveness" (β = 0.509, 95% CI: 0.352 to 0.665) in the multiple linear regression model. The mediation effect model showed that "food responsiveness" accounted for a significant portion (64.2%) of the mediating effect.

Conclusion

Children with ADHD had higher prevalence of overweight and obesity. As an important risk factor, food responsiveness may connect core symptoms of ADHD with obesity.

Selective Modulation of Hippocampal Theta Oscillations in Response to Morphine versus Natural Reward

Despite the overlapping neural circuits underlying natural and drug rewards, several studies have suggested different behavioral and neurochemical mechanisms in response to drug vs. natural rewards. The strong link between hippocampal theta oscillations (4-12 Hz) and reward-associated learning and memory has raised the hypothesis that this rhythm in hippocampal CA1 might be differently modulated by drug- and natural-conditioned place preference (CPP). Time-frequency analysis of recorded local field potentials (LFPs) from the CA1 of freely moving male rats previously exposed to a natural (in this case, food), drug (in this case, morphine), or saline (control) reward cue in the CPP paradigm showed that the hippocampal CA1 theta activity represents a different pattern for entrance to the rewarded compared to unrewarded compartment during the post-test session of morphine- and natural-CPP. Comparing LFP activity in the CA1 between the saline and morphine/natural groups showed that the maximum theta power occurred before entering the unrewarded compartment and after the entrance to the rewarded compartment in morphine and natural groups, respectively. In conclusion, our findings suggest that drug and natural rewards could differently affect the theta dynamic in the hippocampal CA1 region during reward-associated learning and contextual cueing in the CPP paradigm.

Hyperpalatable Foods Consumption in a Representative Sample of the General Population in Brazil: Differences of Binge and Non-Binge Eating Meals

The availability of hyper-palatable foods (HPF) increased over the past three decades worldwide, a period when eating disorders (ED) and obesity have become global public health concerns. The present study aimed to assess HPF consumption during binge and non-binge meals in a representative sample of adults with and without ED from a metropolitan city in Brazil. A total of 2297 individuals were interviewed in their homes by trained lay interviewers to assess the presence of binge eating disorder (BED), bulimia nervosa (BN), and recurrent binge eating (RBE). Information on their food consumption in objective and subjective binge eating episodes (OBE and SBE, respectively), as well as in the 24 h food recall were obtained. Individuals from the general population consumed 56% of their total calories from HPF. In non-binge meals, people with BN consumed substantially fewer calories from HPF than BED (63% vs. 48%) and RBE (63% vs. 48%) groups. During OBE, participants consumed an average of 70% of the calories from HPF, with no between-group differences. During SBE, subjects with BN consumed substantially fewer calories from HPF than those with BED (76% vs. 50%). In conclusion, HPF were highly consumed by the Brazilian population. However, there was a greater impact on BED and RBE subjects and during binge eating episodes.

Effect of exposure to endocrine disrupting chemicals in obesity and neurodevelopment: The genetic and microbiota link

Current evidence highlights the importance of the genetic component in obesity and neurodevelopmental disorders (attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD) and intellectual disability (ID)), given that these diseases have reported an elevated heritability. Additionally, environmental stressors, such as endocrine disrupting chemicals (EDCs) have been classified as obesogens, neuroendocrine disruptors, and microbiota disrupting chemicals (MDCs). For this reason, the importance of this work lies in examining two possible biological mechanistic pathways linking obesity and neurodevelopmental/behavioural disorders: EDCs - gene and EDCs - microbiota interactions. First, we summarise the shared mechanisms of action of EDCs and the common genetic profile in the bidirectional link between obesity and neurodevelopment. In relation to interaction models, evidence from the reviewed studies reveals significant interactions between pesticides/heavy metals and gene polymorphisms of detoxifying and neurotransmission systems and metal homeostasis on cognitive development, ASD and ADHD symptomatology. Nonetheless, available literature about obesity is quite limited. Importantly, EDCs have been found to induce gut microbiota changes through gut-brain-microbiota axis conferring susceptibility to obesity and neurodevelopmental disorders. In view of the lack of studies assessing the impact of EDCs - gene interactions and EDCs - mediated dysbiosis jointly in obesity and neurodevelopment, we support considering genetics, EDCs exposure, and microbiota as interactive factors rather than individual contributors to the risk for developing obesity and neurodevelopmental disabilities at the same time.

Underreporting of energy intake is not associated with the reported consumption of NOVA-classified food groups in socially vulnerable women

Few studies have investigated which types of food are least reported among underreporters of energy intake (EI). This study assessed the association between the underreporting of EI and the consumption report of food groups according to NOVA classification in women in social vulnerability. EI was measured through three 24-h dietary recalls administered by the research team. Total energy expenditure (TEE) was evaluated using the doubly labelled water method. The percentage of EI arising from each NOVA group food classification (unprocessed/minimally processed foods, culinary ingredients, processed foods and ultra-processed foods [UPF]) was calculated. The agreement between the EI and the TEE was assessed using the ratio EI:TEE. Associations were assessed with Pearson's correlation and multivariable linear regression, adjusted for age, education and body fat. The sample (63 women, age: 30.8 years, Body Mass Index: 27.6 kg/m² ) reported an EI of 1849 kcal and a TEE of 2223 kcal, with a mean EI:TEE of 0.85. There were no significant correlations between the EI:TEE and the reported food intake according to NOVA classifications. Multivariable linear regression also did not show any significant associations (UPF: 8.47, 95% CI: [-3.65; 20.60] %kcal; Processed: -6.85, [-19.21; 7.71] %kcal; Culinary ingredients: 1.30 [-5.10; 7.71] %kcal; Unprocessed/minimally processed: -2.92 [-10.98; 5.13] %kcal). In conclusion, socially vulnerable women that underreport their EI do not report a lower intake of any specific group of foods according to NOVA classification.

More complex than you might think: Neural representations of food reward value in obesity

Obesity reached pandemic proportions and weight-loss treatments are mostly ineffective. The level of brain activity in the reward circuitry is proposed to be proportionate to the reward value of food stimuli, and stronger in people with obesity. However, empirical evidence is inconsistent. This may be due to the double-sided nature of high caloric palatable foods: at once highly palatable and high in calories (unhealthy). This study hypothesizes that, viewing high caloric palatable foods, a hedonic attentional focus compared to a health and a neutral attentional focus elicits more activity in reward-related brain regions, mostly in people with obesity. Moreover, caloric content and food palatability can be decoded from multivoxel patterns of activity most accurately in people with obesity and in the corresponding attentional focus. During one fMRI-session, attentional focus (hedonic, health, neutral) was manipulated using a one-back task with individually tailored food stimuli in 32 healthy-weight people and 29 people with obesity. Univariate analyses (p < 0.05, FWE-corrected) showed that brain activity was not different for palatable vs. unpalatable foods, nor for high vs. low caloric foods. Instead, this was higher in the hedonic compared to the health and neutral attentional focus. Multivariate analyses (MVPA) (p < 0.05, FDR-corrected) showed that palatability and caloric content could be decoded above chance level, independently of either BMI or attentional focus. Thus, brain activity to visual food stimuli is neither proportionate to the reward value (palatability and/or caloric content), nor significantly moderated by BMI. Instead, it depends on people's attentional focus, and may reflect motivational salience. Furthermore, food palatability and caloric content are represented as patterns of brain activity, independently of BMI and attentional focus. So, food reward value is reflected in patterns, not levels, of brain activity.

Food Addiction: A Comprehensive Review

Food addiction is associated with dysfunctions in the reward circuit, such as hyperresponsiveness during the exposure to high-calorie flavors in overweight and obese individuals. Similar to drug addiction, there is also impaired self-regulatory control supported by deregulation of the frontostriatal circuit. The inclusion of validated measures of food addiction in clinical research, such as the Yale Food Addiction Scale, has increased the understanding of the clinical utility of this concept. Furthermore, food addiction, eating disorders, and obesity are interrelated. Thus, it is important to recognize food addiction among individuals affected by obesity and candidates for bariatric surgery (ie, preoperative and postoperative assessment). In this context, it has been reported that food addiction may impede weight loss and increase the likelihood of regaining weight when associated with personality traits such as neuroticism and impulsiveness, which are also related to mood disorders, anxiety, and addictive behaviors.

No significant effect of frequent online sexual behaviour on Pavlovian-to-instrumental transfer (PIT): Implications for compulsive sexual behaviour disorder

Reward based learning is broadly acknowledged to underpin the development and maintenance of addictive behaviour although the mechanism in sexual compulsivity is less understood. Using a Pavlovian-to-Instrumental Transfer (PIT) task we tested whether the motivational aspect of conditioned Pavlovian conditioned stimulus invigorated instrumental responding in relation to specific compatible monetary rewards. Performance on the task was analysed between two groups of males based on Low (N = 38) and High (N = 41) self-report online sexual behaviour (OSB). Psychometric tests including sexual compulsivity scale and behavioural activation/behavioural inhibition (BIS/BAS) were also administered to determine the relationship between OSB and general reward sensitivity. We show clear evidence of acquisition in the Pavlovian and instrumental conditioning phases. Specific transfer effect was greater in the High-OSB group although the difference compared to the Low-OSB group was non-significant. OSB negatively correlated with both BIS and BAS indicative of introversion and low reward sensitivity. OSB positively correlated with sexual compulsivity although it is unclear whether individuals in the High-OSB group considered their behaviour either excessive or problematic. These findings contribute to the ongoing debate regarding the nature of problematic OSB. Fundamental differences in motivational characteristics and mechanism contributing to compulsive behaviour in relation to high-OSB might indicate incompatibility with behavioural addiction models. PIT was not enhanced in high-OSB by appetitive conditioning, although problematic OSB could stem from failure to inhibit actions. Further research should investigate whether aversive conditioning differentially affects responding in high-OSB individuals, potentially explaining perseverant behaviour despite negative consequences.

Inflammation in VTA Caused by HFD Induces Activation of Dopaminergic Neurons Accompanied by Binge-like Eating

Binge eating is a characteristic symptom observed in obese individuals that is related to dysfunction of dopaminergic neurons (DNs). Intermittent administration of a high-fat diet (HFD) is reported to induce binge-like eating, but the underlying mechanisms remain unclear. We generated dopaminergic neuron specific IKKβ deficient mice (KO) to examine the effects of inflammation in DNs on binge-like eating under inflammatory conditions associated with HFD. After administration of HFD for 4 weeks, mice were fasted for 24 h, and then the consumption of HFD was measured for 2 h. We also evaluated that the mRNA expressions of inflammatory cytokines, glial markers, and dopamine signaling-related genes in the ventral tegmental area (VTA) and striatum. Moreover, insulin was administered intraventricularly to assess downstream signaling. The consumption of HFD was significantly reduced, and the phosphorylation of AKT in the VTA was significantly increased in female KO compared to wild-type (WT) mice. Analyses of mRNA expressions revealed that DNs activity and inflammation in the VTA were significantly decreased in female KO mice. Thus, our data suggest that HFD-induced inflammation with glial cell activation in the VTA affects DNs function and causes abnormal eating behaviors accompanied by insulin resistance in the VTA of female mice.

The Burden of Carbohydrates in Health and Disease

Foods high in carbohydrates are an important part of a healthy diet, since they provide the body with glucose to support bodily functions and physical activity. However, the abusive consumption of refined, simple, and low-quality carbohydrates has a direct implication on the physical and mental pathophysiology. Then, carbohydrate consumption is postulated as a crucial factor in the development of the main Western diseases of the 21st century. We conducted this narrative critical review using MedLine (Pubmed), Cochrane (Wiley), Embase, and CinAhl databases with the MeSH-compliant keywords: carbohydrates and evolution, development, phylogenetic, GUT, microbiota, stress, metabolic health, consumption behaviors, metabolic disease, cardiovascular disease, mental disease, anxiety, depression, cancer, chronic kidney failure, allergies, and asthma in order to analyze the impact of carbohydrates on health. Evidence suggests that carbohydrates, especially fiber, are beneficial for the well-being and growth of gut microorganisms and consequently for the host in this symbiotic relationship, producing microbial alterations a negative effect on mental health and different organic systems. In addition, evidence suggests a negative impact of simple carbohydrates and refined carbohydrates on mood categories, including alertness and tiredness, reinforcing a vicious circle. Regarding physical health, sugar intake can affect the development and prognosis of metabolic disease, as an uncontrolled intake of refined carbohydrates puts individuals at risk of developing metabolic syndrome and subsequently developing metabolic disease.

Mediating effect of self-control in the relationship between psychological distress and food addiction among college students

Psychological distress is a possible trigger contributing to food addiction, which is characterized by a loss of behavioral control and compulsive food intake. However, little is known about its underlying mechanisms. Self-control, an important self-regulation skill, may mediate the effect of psychological distress on food addiction. A cross-sectional survey was used to explore the direct relationship between psychological distress and food addiction, and the mediating role of self-control in this relationship. Food addiction, psychological distress, and self-control were evaluated using the Chinese versions of the Yale Food Addiction Scale 2.0, Depression-Anxiety-Stress Scale, and Self-control Scale, respectively. Correlation analyses showed that food addiction was positively correlated with psychological distress, but negatively related to self-control. Structural equation modeling revealed the mediating role of self-control in the relationship between food addiction and psychological distress. As a significant predictor of food addiction, psychological distress may induce food addiction directly or indirectly through the effect of self-control. These findings provide a deeper understanding of the relationship between psychological distress and food addiction, and the underlying mechanism. As such, psychological distress and self-control should be included in prevention and intervention strategies to address food addiction among college students.

The influence of the subcortex and brain stem on overeating: How advances in functional neuroimaging can be applied to expand neurobiological models to beyond the cortex

Functional neuroimaging has become a widely used tool in obesity and eating disorder research to explore the alterations in neurobiology that underlie overeating and binge eating behaviors. Current and traditional neurobiological models underscore the importance of impairments in brain systems supporting reward, cognitive control, attention, and emotion regulation as primary drivers for overeating. Due to the technical limitations of standard field strength functional magnetic resonance imaging (fMRI) scanners, human neuroimaging research to date has focused largely on cortical and basal ganglia effects on appetitive behaviors. The present review draws on animal and human research to highlight how neural signaling encoding energy regulation, reward-learning, and habit formation converge on hypothalamic, brainstem, thalamic, and striatal regions to contribute to overeating in humans. We also consider the role of regions such as the mediodorsal thalamus, ventral striatum, lateral hypothalamus and locus coeruleus in supporting habit formation, inhibitory control of food craving, and attentional biases. Through these discussions, we present proposals on how the neurobiology underlying these processes could be examined using functional neuroimaging and highlight how ultra-high field 7-Tesla (7 T) fMRI may be leveraged to elucidate the potential functional alterations in subcortical networks. Focus is given to how interactions of these regions with peripheral endocannabinoids and neuropeptides, such as orexin, could be explored. Technical and methodological aspects regarding the use of ultra-high field 7 T fMRI to study eating behaviors are also reviewed.

Association between Leptin (G2548A) and Leptin Receptor (Q223R) Polymorphisms with Plasma Leptin, BMI, Stress, Sleep and Eating Patterns among the Multiethnic Young Malaysian Adult Population from a Healthcare University

Relative leptin resistance in childhood to absolute leptin resistance in maturity suggests sleep, eating behaviour, and the psychological state as probable causes. The current body of research provides inconclusive evidence linking G2548A and Q223R to obesity. Furthermore, we could find very little data that have observed the association between the environment and gene polymorphism, especially in the multiethnic population that exists in Malaysia. This study searched for a possible link between sleeping habits, eating behaviour, and stress indicators with plasma leptin and its genetic variation in young adult Malaysian healthcare students. The study involved 185 first- and second-year medical and dental students from a healthcare university. Polymerase Chain Reaction−Restriction Fragment Length Polymorphism(PCR-RFLP) determined the genotype, Enzyme Linked Immunoabsorbant Assay (ELISA) tested the serum leptin, and a self-administered questionnaire evaluated sleep, eating behaviour, and psychological condition. Gender and ethnicity are linked to fasting plasma leptin levels (p < 0.001). Plasma leptin also affects stress, anxiety, and sadness. Leptin (LEP) and Leptin Receptor (LEPR) polymorphisms were not associated with BMI, plasma leptin, sleep, eating behaviour, or psychological state. Young adult Malaysian Indians were obese and overweight, while Chinese were underweight. These findings imply overweight and obese participants were in stage I of leptin resistance and lifestyle change or leptin therapy could prevent them from becoming cripplingly obese as they age.

An evidence review of the association of immune and inflammatory markers with obesity-related eating behaviors

Background

Eating behaviors contribute to disproportionate energy intake and are linked to the development of obesity. Animal studies support the role of inflammatory cytokines and chemokines in the regulation of obesity-related eating behaviors and offer a potential target to combat obesity through the modulation of inflammation. However, more complex eating behaviors are present in humans, and their relationships with immune/inflammation markers are unclear. The present study reviewed current literature to synthesize the evidence on the association of immune/inflammation markers with obesity-related eating behaviors in humans.

Methods

A systematic search of three electronic databases yielded 811 articles, of which 11 met the inclusion criteria.

Results

The majority of the included studies (91%) were either case-control or cross-sectional studies. A variety of immune/inflammation markers and obesity-related eating behaviors have been assessed in the chosen studies. Three out of four studies identified a positive relationship between C-reactive protein (CRP)/high-sensitivity CRP and loss of control eating. Other inflammatory markers that potentially have a positive relationship with obesity-related eating behaviors include fractalkine and fibrinogen. Additionally, immune molecules, including interferon gamma (INF-γ), interleukin (IL)-7, IL-10, and α-melanocyte-stimulating hormone-reactive immunoglobulin G (α-MSH/IgG) immune complex, may have negative associations with obesity-related eating behaviors. However, most findings were identified by single studies.

Conclusion

Limited studies have been conducted in humans. Current evidence indicates a potential bi-directional relationship between inflammatory/immune markers and obesity-related eating behaviors. Additional studies with sophisticated research design and comprehensive theoretical models are warranted to further delineate the relationship between immune/inflammation markers and obesity-related eating behaviors.

Brain regulation of hunger and motivation: The case for integrating homeostatic and hedonic concepts and its implications for obesity and addiction

Obesity and other eating disorders are marked by dysregulations to brain metabolic, hedonic, motivational, and sensory systems that control food intake. Classic approaches in hunger research have distinguished between hedonic and homeostatic processes, and have mostly treated these systems as independent. Hindbrain structures and a complex network of interconnected hypothalamic nuclei control metabolic processes, energy expenditure, and food intake while mesocorticolimbic structures are though to control hedonic and motivational processes associated with food reward. However, it is becoming increasingly clear that hedonic and homeostatic brain systems do not function in isolation, but rather interact as part of a larger network that regulates food intake. Incentive theories of motivation provide a useful route to explore these interactions. Adapting incentive theories of motivation can enable researchers to better how motivational systems dysfunction during disease. Obesity and addiction are associated with profound alterations to both hedonic and homeostatic brain systems that result in maladaptive patterns of consumption. A subset of individuals with obesity may experience pathological cravings for food due to incentive sensitization of brain systems that generate excessive 'wanting' to eat. Further progress in understanding how the brain regulates hunger and appetite may depend on merging traditional hedonic and homeostatic concepts of food reward and motivation.

Functional Magnetic Resonance Imaging and Obesity-Novel Ways to Seen the Unseen

Obesity remains a pandemic of the 21st century. While there are many causes of obesity and potential treatments that are currently known, source data indicate that the number of patients is constantly increasing. Neural mechanisms have become the subject of research and there has been an introduction of functional magnetic resonance imaging in obesity-associated altered neural signaling. Functional magnetic resonance imaging has been established as the gold standard in the assessment of neuronal functions related to nutrition. Thanks to this, it has become possible to delineate those regions of the brain that show altered activity in obese individuals. An integrative review of the literature was conducted using the keywords ““functional neuroimaging” OR “functional magnetic resonance “OR “fmri” and “obesity” and “reward circuit and obesity” in PubMed and Google Scholar databases from 2017 through May 2022. Results in English and using functional magnetic resonance imaging to evaluate brain response to diet and food images were identified. The results from functional magnetic resonance imaging may help to identify relationships between neuronal mechanisms and causes of obesity. Furthermore, they may provide a substrate for etiology-based treatment and provide new opportunities for the development of obesity pharmacotherapy.

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.

Neuropeptide Y interaction with dopaminergic and serotonergic pathways: interlinked neurocircuits modulating hedonic eating behaviours

Independent from homeostatic needs, the consumption of foods originating from hyperpalatable diets is defined as hedonic eating. Hedonic eating can be observed in many forms of eating phenotypes, such as compulsive eating and stress-eating, heightening the risk of obesity development. For instance, stress can trigger the consumption of palatable foods as a type of coping strategy, which can become compulsive, particularly when developed as a habit. Although eating for pleasure is observed in multiple maladaptive eating behaviours, the current understanding of the neurobiology underlying hedonic eating remains deficient. Intriguingly, the combined orexigenic, anxiolytic and reward-seeking properties of Neuropeptide Y (NPY) ignited great interest and has positioned NPY as one of the core neuromodulators operating hedonic eating behaviours. While extensive literature exists exploring the homeostatic orexigenic and anxiolytic properties of NPY, the rewarding effects of NPY continue to be investigated. As deduced from a series of behavioural and molecular-based studies, NPY appears to motivate the consumption and enhancement of food-rewards. As a possible mechanism, NPY may modulate reward-associated monoaminergic pathways, such as the dopaminergic and serotoninergic neural networks, to modulate hedonic eating behaviours. Furthermore, potential direct and indirect NPYergic neurocircuitries connecting classical homeostatic and hedonic neuropathways may also exist involving the anti-reward centre the lateral habenula. Therefore, this review investigates the participation of NPY in orchestrating hedonic eating behaviours through the modulation of monoaminergic pathways.

Association of the dopamine D2 receptor rs1800497 polymorphism with food addiction, food reinforcement, and eating behavior in Chilean adults

PURPOSE

The regulation of food intake and body weight involves two interacting systems: (a) The homeostatic system (including biological regulators of hunger and satiety) and (b) the non-homeostatic system, (involving concepts of food reinforcement and food addiction). Studies have established a strong genetic component in eating behavior and obesity. The TaqI A1 polymorphism (rs1800497) has previously been associated with eating behavior, diminished dopamine D2 receptor (DRD2) density, higher body mass, and food reinforcement, but relations to food addiction remain unclear.

AIM

To evaluate the association between the polymorphism rs1800497 with eating behavior, food reinforcement and food addiction in Chilean adults.

METHODS

This cross-sectional study recruited a convenience sample of 97 obese, 25 overweight and 99 normal-weight adults (18-35 years). Anthropometric measurements were performed by standard procedures. Eating behavior was assessed using the: Yale Food Addiction Scale (YFAS), the Three Factor Eating Behavior Questionnaire and the Food Reinforcement Value Questionnaire (FRVQ). The DRD2 genotype (rs1800497) was determined by taqman assays.

RESULTS

Twenty-two percentage of the participants met the criteria for food addiction. Food addiction was higher in women than men (26% vs 10.7%) and in obese compared to non-obese (40% vs 6%). There was no relationship between food addiction and DRD2 genotype. However when stratified by sex and nutritional status, obese female carriers of the A1 allele reported greater scores on emotional eating and snack food reinforcement compared to non-carriers.

CONCLUSIONS

The DRD2 polymorphism is associated with some hedonic aspects of eating behavior, namely food reinforcement and emotional eating but not food addiction, and this association may be moderated by sex and obesity status, with obese women who are carriers of this genetic variant at higher risk.

LEVEL OF EVIDENCE

Level V: evidence obtained from a cross-sectional descriptive study.

Taste of Fat and Obesity: Different Hypotheses and Our Point of View

Obesity results from a temporary or prolonged positive energy balance due to an alteration in the homeostatic feedback of energy balance. Food, with its discriminative and hedonic qualities, is a key element of reward-based energy intake. An alteration in the brain reward system for highly palatable energy-rich foods, comprised of fat and carbohydrates, could be one of the main factors involved in the development of obesity by increasing the attractiveness and consumption of fat-rich foods. This would induce, in turn, a decrease in the taste of fat. A better understanding of the altered reward system in obesity may open the door to a new era for the diagnosis, management and treatment of this disease.

Weight Status Modulated Brain Regional Homogeneity in Long-Term Male Smokers

BACKGROUND

Tobacco smoking and being overweight could lead to adverse health effects, which remain an important public health problem worldwide. Research indicates that overlapping pathophysiology may contribute to tobacco addiction and being overweight, but the neurobiological interaction mechanism between the two factors is still unclear.

METHODS

The current study used a mixed sample design, including the following four groups: (i) overweight long-term smokers (n = 24); (ii) normal-weight smokers (n = 28); (iii) overweight non-smokers (n = 19), and (iv) normal-weight non-smokers (n = 28), for a total of 89 male subjects. All subjects underwent resting-state functional magnetic resonance imaging (rs-fMRI). Regional homogeneity (ReHo) was used to compare internal cerebral activity among the four groups. Interaction effects between tobacco addiction and weight status on ReHo were detected using a two-way analysis of variance, correcting for age, years of education, and head motion.

RESULTS

A significant interaction effect between tobacco addiction and weight status is shown in right superior frontal gyrus. Correlation analyses show that the strengthened ReHo value in the right superior frontal gyrus is positively associated with pack-year. Besides, the main effect of tobacco addiction is specially observed in the occipital lobe and cerebellum posterior lobe. As for the main effect of weight status, the right lentiform nucleus, left postcentral gyrus, and brain regions involved in default mode network (DMN) survived.

CONCLUSIONS

These results shed light on an antagonistic interaction on brain ReHo between tobacco addiction and weight status in the right superior frontal gyrus, which may be a clinical neuro-marker of comorbid tobacco addiction and overweight. Our findings may provide a potential target to develop effective treatments for the unique population of comorbid tobacco addiction and overweight people.

Microbiota and body weight control: Weight watchers within?

Background

Despite several decades of research, managing body weight remains an unsolved clinical problem. Health problems associated with dysregulated body weight, such as obesity and cachexia, exhibit several gut microbiota alterations. There is an increased interest in utilising the gut microbiota for body weight control, as it responds to intervention and plays an important role in energy extraction from food, as well as biotransformation of nutrients.

Scope of the review

This review provides an overview of the role of the gut microbiota in the physiological and metabolic alterations observed in two body weight dysregulation-related disorders, namely obesity and cachexia. Second, we assess the available evidence for different strategies, including caloric restriction, intermittent fasting, ketogenic diet, bariatric surgery, probiotics, prebiotics, synbiotics, high-fibre diet, and fermented foods – effects on body weight and gut microbiota composition. This approach was used to give insights into the possible link between body weight control and gut microbiota configuration.

Major conclusions

Despite extensive associations between body weight and gut microbiota composition, limited success could be achieved in the translation of microbiota-related interventions for body weight control in humans. Manipulation of the gut microbiota alone is insufficient to alter body weight and future research is needed with a combination of strategies to enhance the effects of lifestyle interventions.

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The gut microbiota is involved in the control of nutrient availability, appetite, and body weight.

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Both obesity and cachexia are associated with altered gut microbiota.

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Specific dietary and surgical approaches positively impact body weight and gut microbiota.

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Manipulation of the gut microbiota alone is insufficient to alter body weight in humans.

Molecular aspects of fructose metabolism and metabolic disease

Excessive sugar consumption is increasingly considered as a contributor to the emerging epidemics of obesity and the associated cardiometabolic disease. Sugar is added to the diet in the form of sucrose or high-fructose corn syrup, both of which comprise nearly equal amounts of glucose and fructose. The unique aspects of fructose metabolism and properties of fructose-derived metabolites allow for fructose to serve as a physiological signal of normal dietary sugar consumption. However, when fructose is consumed in excess, these unique properties may contribute to the pathogenesis of cardiometabolic disease. Here, we review the biochemistry, genetics, and physiology of fructose metabolism and consider mechanisms by which excessive fructose consumption may contribute to metabolic disease. Lastly, we consider new therapeutic options for the treatment of metabolic disease based upon this knowledge.

Lower ΔFosB expression in the dopaminergic system after stevia consumption in rats housed under environmental enrichment conditions

Environmental enrichment (EE) has been proven to reduce drug seeking and the development of addiction-related behaviors in rodent models, but the effects of EE on natural reward acquisition in the form of sweet beverages are poorly understood. Accumulating evidence shows that the intake of sugar, the main ingredient of sweet beverages, alters the dopaminergic system, leading to addiction-related physiological and molecular changes. Sugar in sweet beverages has been replaced with natural sweeteners, such as stevia extract, which has greater sweetener potential but no energy content. Our research group found that sucralose consumption increased the expression of ΔFosB in reward-related nuclei, suggesting activation of the dopaminergic system. The present study assessed the effects of EE on stevia consumption and the expression of ΔFosB in the nucleus accumbens, caudate putamen, and prefrontal cortex. Sixteen male Wistar rats, 21 days old, were randomly assigned to an EE group (n = 8) or standard environment (SE) group (n = 8) and reared for 30 days. On postnatal day 52 (PND52), the brains of four animals in each housing condition were extracted to determine basal ΔFosB levels. Stevia consumption with intermittent access and ΔFosB immunoreactivity were measured for 21 days in the remainder of the rats. Compared with SE animals, EE animals exhibited a reduction of stevia consumption and alterations of ΔFosB immunoreactivity in the reward system. These results indicate that EE reduces stevia consumption and the stevia-induced ΔFosB expression, suggesting addiction-related changes in dopaminergic nuclei, which may be interpreted as a neuroprotective effect.

The Relationship of Food Addiction With Other Eating Pathologies and Impulsivity: A Case-Control Study

The concept of food addiction (FA) has become central in recent years in understanding the psychological etiology of obesity. In this matched case-control study from Turkey, it was aimed to examine the prevalence of FA and related risk factors in four consecutive body mass index (BMI) categories. The case group consisted of pre-operative bariatric surgery patients with BMI over 35.0 kg/m2 (n = 40) and the control group was composed of age- and gender- matching individuals from the other categories, namely obese (n = 35), overweight (n = 40), and normal weight (n = 40). The Yale Food Addiction Scale (YFAS) and a standardized clinical interview using the DSM-5 substance use disorders criteria adopted for FA, the Eating Disorder Examination Questionnaire (EDEQ) and the Barratt Impulsivity Scale (BIS-11) were used as assessment instruments. It was found that FA was significantly associated with more serious eating pathologies, more frequent weight-cycling and earlier onset of dieting, higher impulsivity, and higher BMI. Motor and total impulsivity scores showed a positive albeit week correlation with the severity of FA but no significant correlation with BMI, indicating a relationship between impulsivity and weight gain in some but not all individuals. The severity of FA predicted the increase in BMI. Our findings suggest that FA is associated with weight gain in a group of individuals, plausibly through impulsive overeating. Emphasis on FA and its clinical implications such as addiction-based treatments may improve outcomes in obesity and facilitate health promotion.

Associations of Stress and Appetite Hormones with Binge Eating in Females with Anorexia Nervosa after Weight Restoration: A Longitudinal Study

Binge eating is a transdiagnostic eating disorder symptom that can occur in patients with anorexia nervosa (AN), persisting after weight restoration, and impeding their recovery. However, little is known about the biological predictors of binge eating after AN weight restoration. The goals of this exploratory study of 73 females with AN were: (1) to examine changes in cortisol, the adrenocorticotropic hormone, norepinephrine, ghrelin (total and active), and leptin levels across the admission, discharge, and 3 months post-discharge from the inpatient AN weight restoration; and (2) to determine whether the target hormones were associated with objective or subjective binge eating (OBE or SBE). The participants completed the self-reported Eating Disorder Examination Questionnaire, Beck Anxiety Inventory, and Beck Depression Inventory-II, and provided fasting whole blood samples for hormone assays. The results showed significant changes in body mass index (BMI), cortisol, total ghrelin, and leptin levels over the three time points. The cortisol levels at admission and discharge were significantly associated with the number of SBE episodes at 3 months post-discharge. Findings suggest the need to replicate and confirm the role of cortisol in predicting the emergence of SBE and uncover the mechanisms underlying SBE and cortisol to prevent SBE and its negative consequences.

Obesity as a Condition Determined by Food Addiction: Should Brain Endocannabinoid System Alterations Be the Cause and Its Modulation the Solution?

Obesity is a complex disorder, and the number of people affected is growing every day. In recent years, research has confirmed the hypothesis that food addiction is a determining factor in obesity. Food addiction is a behavioral disorder characterized by disruptions in the reward system in response to hedonic eating. The endocannabinoid system (ECS) plays an important role in the central and peripheral control of food intake and reward-related behaviors. Moreover, both obesity and food addiction have been linked to impairments in the ECS function in various brain regions integrating peripheral metabolic signals and modulating appetite. For these reasons, targeting the ECS could be a valid pharmacological therapy for these pathologies. However, targeting the cannabinoid receptors with inverse agonists failed when used in clinical contexts as a consequence of the induction of affective disorders. In this context, new classes of drugs acting either on CB1 and/or CB2 receptors or on synthetic and degradation enzymes of endogenous cannabinoids are being studied. However, further investigation is necessary to find safe and effective treatments that can exert anti-obesity effects, normalizing reward-related behaviors without causing important adverse mood effects.

Peter JV. Sugars and Sweet Taste: Addictive or Rewarding?

The notion of food "addiction" often focuses on the overconsumption of sweet tasting foods or so-called sugar "addiction". In the extreme, some have suggested that sugar and sweet tastes elicit neural and behavioral responses analogous to those observed with drugs of abuse. These concepts are complicated by the decades long uncertainty surrounding the validity and reproducibility of functional magnetic resonance imaging (fMRI) methodologies used to characterize neurobiological pathways related to sugar and sweet taste stimuli. There are also questions of whether sweet taste or post-ingestion metabolic consequences of sugar intake would lead to addiction or excessive caloric intake. Here, we present a focused narrative review of literature related to the reward value of sweet taste which suggests that reward value can be confounded with the construct of "addictive potential". Our review seeks to clarify some key distinctions between these constructs and questions the applicability of the addiction construct to human over-eating behaviors. To adequately frame this broad discussion requires the flexibility offered by the narrative review paradigm. We present selected literature on: techniques used to link sugar and sweet tastes to addiction neurobiology and behaviors; sugar and sweet taste "addiction"; the relationship of low calorie sweetener (LCS) intake to addictive behaviors and total calorie intake. Finally, we examined the reward value of sweet tastes and contrasted that with the literature describing addiction. The lack of reproducibility of fMRI data remains problematic for attributing a common neurobiological pathway activation of drugs and foods as conclusive evidence for sugar or sweet taste "addiction". Moreover, the complicated hedonics of sweet taste and reward value are suggested by validated population-level data which demonstrate that the consumption of sweet taste in the absence of calories does not increase total caloric intake. We believe the neurobiologies of reward value and addiction to be distinct and disagree with application of the addiction model to sweet food overconsumption. Most hypotheses of sugar "addiction" attribute the hedonics of sweet foods as the equivalent of "addiction". Further, when addictive behaviors and biology are critically examined in totality, they contrast dramatically from those associated with the desire for sweet taste. Finally, the evidence is strong that responses to the palatability of sweets rather than their metabolic consequences are the salient features for reward value. Thus, given the complexity of the controls of food intake in humans, we question the usefulness of the "addiction" model in dissecting the causes and effects of sweet food over-consumption.

Post-traumatic stress disorder may set the neurobiological stage for eating disorders: A focus on glutamatergic dysfunction

Post-traumatic stress disorder (PTSD) is a trauma and stress-related disorder which has been shown to be highly comorbid with, and commonly a precedent of, the eating disorders anorexia nervosa, bulimia nervosa, and binge eating disorder. The objective of this review is to discuss a potential overlapping neurobiological mechanism for this comorbidity. Alterations in glutamatergic neurotransmission have been observed in all four of the aforementioned disorders. Excessive excitation via glutamate contributes to excitotoxicity, and over-activation of the hypothalamic-pituitary-adrenal axis, both of which have implications for the deterioration of various brain structures. Prominent structures impacted include the hippocampus, hypothalamus, and prefrontal cortex, all of which are integral to the regulation of stress and eating. The current review suggests that altered glutamate function by trauma or extreme stress may facilitate PTSD and subsequent eating disorder onset, and that glutamatergic modulation may be a key treatment for individuals suffering from these conditions. This overlapping mechanism may help inform future research on individuals with comorbid PTSD and eating disorders, and it could also help inform ways to potentially prevent the onset of these conditions.

A narrative review of reward sensitivity, rash impulsivity, and food addiction in adolescents

Adolescence represents a neurodevelopmental period characterised by heightened reward drive and weaker inhibitory control that may increase vulnerability to compulsive overconsumption of highly-palatable foods and food addiction. This narrative review aimed to summarise research investigating the presence of food addiction in adolescents and establish the role that impulsivity traits (i.e., reward sensitivity and rash impulsivity), previously linked to substance and behavioural addictions, play in contributing to food addiction in this cohort. It was found that the prevalence of food addiction was typically higher in studies that recruited adolescents who were overweight/obese or from clinical populations. Overall, impulsivity was found to be more consistently associated with food addiction, while the relationships between measures of reward sensitivity and food addiction were mixed. Findings of this review suggest trait impulsivity may contribute to food addiction in adolescents, however, further longitudinal and prospective research is recommended to confirm these findings and to investigate the potential interactive effects of reward sensitivity and rash impulsivity.