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.

Interactive influences of food, contexts and neurocognitive systems on addictive eating

Compulsive eating is a common symptom of different conditions, including obesity, binge eating disorder and bulimia. One hypothesis is that contemporary food products promote compulsive eating via addiction-like mechanisms. However, what is the addictive substance in food, and what is the phenotypic overlap between obesity / eating disorders and addictions are questions that remain unresolved. In this review, we applied a multilevel framework of addiction, which encompasses the 'drug' (certain foods), the person's mindset, and the context, to improve understanding of compulsive eating. Specifically, we reviewed evidence on the addictive properties of specific foods, the neurocognitive systems that control dietary choices, and their interaction with physical, emotional and social contexts. We focused on different target groups to illustrate distinct aspects of the proposed framework: the impact of food and contextual factors were examined across a continuum, with most studies conducted on healthy participants and subclinical populations, whereas the review of neurocognitive aspects focused on clinical groups in which the alterations linked to addictive and compulsive eating are particularly visible. The reviewed evidence suggest that macronutrient composition and level of processing are associated with the addictive properties of food; there are overlapping neuroadaptations in reward and decision-making circuits across compulsive eating conditions; and there are physical and social contexts that fuel compulsive eating by exploiting reward mechanisms and their interaction with emotions. We conclude that a biopsychosocial model that integrates food, neurobiology and context can provide a better understanding of compulsive eating manifestations in a transdiagnostic framework.

The Effect of Food Composition and Behavior on Neurobiological Response to Food: a Review of Recent Research

PURPOSE OF REVIEW

Controversy surrounds the construct of food addiction. The current review examines neurobiological evidence for the existence of food addiction as a valid diagnosis.

RECENT FINDINGS

Recent neuroimaging studies suggest significant overlap in the areas of the brain that are activated in relation to both food and drug addiction. Specifically, areas of the brain implicated in executive functioning (e.g., attention, planning, decision-making, inhibition), pleasure and the experience of reward, and sensory input and motor functioning display increased activation among individuals with symptoms of both food and drug addiction. Proposed symptoms of food addiction mirror those comprising other substance use disorder diagnoses, with similar psychological and behavioral sequelae. Results of neuroimaging studies suggest significant overlap in the areas of the brain that are activated in relation to both food and drug addiction, providing support for continued research into the construct of food addiction.

Relating goal-directed behaviour to grazing in persons with obesity with and without eating disorder features

BACKGROUND

Both obesity and eating disorders (ED) have been associated with reductions in purposeful, flexible goal-directed behaviour, and with an overreliance on more rigid habitual behaviour. It is currently unknown whether grazing, an eating style which is common in both conditions, is related to goal-directed behaviour. The current study therefore aimed to relate grazing to goal-directed behaviour in a group of participants with obesity with and without ED features, compared to a healthy-weight control group.

METHODS

Participants (N = 87; 67.8% women, mean age 28.57 years), of whom 19 had obesity and significant eating disorder features, 25 had obesity but without marked eating disorder features, and 43 were age- and sex-matched healthy-weight controls, completed two instrumental learning tasks assessing action-outcome contingency sensitivity and devaluation sensitivity, as well as demographic and eating disorder-related questionnaires. Gamma and Ordinary Least Squares regressions were performed to examine the effect of group and grazing on goal-directed behaviour.

RESULTS

Lower action-outcome contingency sensitivity was found in the group with obesity and with eating disorder features than in the group with obesity but without eating disorder features or in healthy controls. No group differences in devaluation sensitivity were found. A small but significant relationship was found between grazing severity and contingency sensitivity in the group with obesity and eating disorder features, such that increasing grazing severity was associated with less diminished contingency sensitivity.

CONCLUSIONS

There is some indication that in persons with obesity and eating disorder features instrumental behaviour is less flexible and adaptive; furthermore, within this group grazing may represent a goal-directed behaviour, despite unhelpful long-term implications of grazing.

Grazing behaviour and associations with obesity, eating disorders, and health-related quality of life in the Australian population

BACKGROUND

Grazing, including a compulsive subtype, represents an eating behaviour of recent interest in obesity and eating disorders (ED), however, there is little information regarding its prevalence and correlates in the general population. The current study aimed to report on the distribution of compulsive grazing (CG) and non-compulsive grazing (NCG) in the Australian population, and to assess associations with obesity, ED, and health-related functioning.

METHODS

A representative sample of 3047 individuals aged ≥15 years (50.8% female) completed a cross-sectional survey in 2016 assessing grazing, quality of life, BMI, and ED symptoms. Prevalence data were obtained, and logistic regressions and multivariate analyses were conducted to examine relationships between grazing and obesity, ED, and health-related quality of life.

RESULTS

The point prevalence of regular NCG was 38.04% (95% CI [36.33, 39.78]; n = 1159) and CG was 10.24% (95% CI [9.21, 11.37]; n = 312). Persons with regular CG had almost twice the odds of a BMI ≥ 30 than of a BMI in the "healthy" range compared to those with no grazing. CG presented stronger associations with ED features and binge-type ED diagnostic groups than NCG, with high rates found in BED-Broad and BN, although some associations with ED features were also present for NCG. Those with both ED and obesity had an 11-fold increase in the odds of engaging in CG than in no grazing, compared to those without. Mental health-related quality of life was lower in those who engaged in CG in the population, as well as in those with obesity.

CONCLUSIONS

Grazing, especially when associated with a more severe sense of loss of control, is a problematic eating behaviour in the general population, as well as in persons with high BMI, a binge-type ED, or both.

The short inventory of grazing (SIG): development and validation of a new brief measure of a common eating behaviour with a compulsive dimension

BACKGROUND

Grazing, the repetitious and unplanned eating of small amounts of food with or without a sense of loss of control (LOC), is an eating pattern of recent interest which is highly prevalent in eating disorders and obesity. The current study aimed to (1) assess psychometric properties of a short inventory of grazing (SIG), consisting of a "grazing in general" item and a "compulsive/LOC grazing" item and (2) examine associations between compulsive and non-compulsive grazing and body mass index (BMI), eating disorder psychopathology, distress and health-related quality of life.

METHODS

Participants recruited from a university and the community (n = 227; 75.3% female; age = 25.00 (9.88; 17.58-57.17) years; BMI = 23.24 (4.91, 14.20-46.06) kg/m²) completed an online test battery including the SIG. Parametric and non-parametric statistics were computed to assess internal consistency, test-retest reliability and construct validity, to test associations between the SIG and the other study variables, and to examine between-group differences.

RESULTS

The SIG demonstrated appropriate psychometric properties. Results indicated that both grazing in general and low-frequency LOC grazing are common; however, LOC grazing of moderate-severe frequency and/or associated with marked distress is unusual. Frequency of LOC grazing, but not grazing in general, was significantly associated with higher BMI, psychological distress, compensatory behaviours and lower mental health-related quality of life. The presence of compulsive grazing was also associated with eating disorder caseness and binge-type eating disorder diagnostic groups.

CONCLUSIONS

Results support the positioning of "compulsive" LOC grazing on a continuum of problematic eating. The SIG is a parsimonious measure of this eating pattern of emergent interest.

Kleine-Levin syndrome; An update and mini-review

Since 1962, when Critchley and Hoffman coined the term Kleine-Levin Syndrome (KLS) for the triad of hypersomnia, excessive eating and "often abnormal behavior" which they have observed in 11 adolescent boys, the number of patients recognized with this rare syndrome expanded, the spectrum of the clinical presentation, disease course, prognosis, gender specificity and the presence of familial cases were established. However, in spite of the progress made in neuroscience, the search for the cause, neuroanatomy, pathophysiology and drug treatment of KLS is still ongoing. In this mini-review we will describe in some detail the scientific efforts made to understand in depth the complex symptomatology of KLS and refer also to updated findings reached up till now.

Childhood risk factors for lifetime bulimic or compulsive eating by age 30 years in a British national birth cohort

OBJECTIVE

To examine whether previously identified childhood risk factors for bulimia or compulsive eating (BCE) predict self-reported lifetime BCE by age 30 years in a prospective birth cohort.

METHOD

Using data from the 1970 British Cohort Study at birth, 5, and 10 years, associations between 22 putative childhood risk factors and self-reported lifetime BCE at 30 years were examined, adjusting for sex and socioeconomic status.

RESULTS

Only female sex (odds ratio (OR): 9.2; 95% confidence interval (CI): 1.9-43.7; p = 0.005), low self-esteem (OR:2.9; 95%CI: 1.1-7.5; p = 0.03) and high maternal education (OR:5.4; 95%CI: 2.0-14.8; p = 0.001) were significantly associated with higher risk of BCE, whereas high SES at 10 years was significantly protective (OR:0.2; 95%CI: 0.1-0.8; p = 0.022) of BCE in fully adjusted multivariable logistic regression analysis.

DISCUSSION

Our findings do not support a strong role for childhood weight status and eating behaviours in the development of bulimia and compulsive eating pathology, rather suggesting a focus on self esteem may have greater relative importance. Findings in relation to maternal education and SES need further exploration.

The inverse agonist of CB1 receptor SR141716 blocks compulsive eating of palatable food

Dieting and the increased availability of highly palatable food are considered major contributing factors to the large incidence of eating disorders and obesity. This study was aimed at investigating the role of the cannabinoid (CB) system in a novel animal model of compulsive eating, based on a rapid palatable diet cycling protocol. Male Wistar rats were fed either continuously a regular chow diet (Chow/Chow, control group) or intermittently a regular chow diet for 2 days and a palatable, high-sucrose diet for 1 day (Chow/Palatable). Chow/Palatable rats showed spontaneous and progressively increasing hypophagia and body weight loss when fed the regular chow diet, and excessive food intake and body weight gain when fed the palatable diet. Diet-cycled rats dramatically escalated the intake of the palatable diet during the first hour of renewed access (7.5-fold compared to controls), and after withdrawal, they showed compulsive eating and heightened risk-taking behavior. The inverse agonist of the CB1 receptor, SR141716 reduced the excessive intake of palatable food with higher potency and the body weight with greater efficacy in Chow/Palatable rats, compared to controls. Moreover, SR141716 reduced compulsive eating and risk-taking behavior in Chow/Palatable rats. Finally, consistent with the behavioral and pharmacological observations, withdrawal from the palatable diet decreased the gene expression of the enzyme fatty acid amide hydrolase in the ventromedial hypothalamus while increasing that of CB1 receptors in the dorsal striatum in Chow/Palatable rats, compared to controls. These findings will help understand the role of the CB system in compulsive eating.