‘Food addiction’ and its association with a dopaminergic multilocus genetic profile

Insulin, Central Dopamine D2 Receptors, and Monetary Reward Discounting in Obesity

Animal research finds that insulin regulates dopamine signaling and reward behavior, but similar research in humans is lacking. We investigated whether individual differences in body mass index, percent body fat, pancreatic β-cell function, and dopamine D2 receptor binding were related to reward discounting in obese and non-obese adult men and women. Obese (n = 27; body mass index>30) and non-obese (n = 20; body mass index<30) adults were assessed for percent body fat with dual-energy X-ray absorptiometry and for β-cell function using disposition index. Choice of larger, but delayed or less certain, monetary rewards relative to immediate, certain smaller monetary rewards was measured using delayed and probabilistic reward discounting tasks. Positron emission tomography using a non-displaceable D2-specific radioligand, [¹¹C](N-methyl)benperidol quantified striatal D2 receptor binding. Groups differed in body mass index, percent body fat, and disposition index, but not in striatal D2 receptor specific binding or reward discounting. Higher percent body fat in non-obese women related to preference for a smaller, certain reward over a larger, less likely one (greater probabilistic discounting). Lower β-cell function in the total sample and lower insulin sensitivity in obese related to stronger preference for an immediate and smaller monetary reward over delayed receipt of a larger one (greater delay discounting). In obese adults, higher striatal D2 receptor binding related to greater delay discounting. Interestingly, striatal D2 receptor binding was not significantly related to body mass index, percent body fat, or β-cell function in either group. Our findings indicate that individual differences in percent body fat, β-cell function, and striatal D2 receptor binding may each contribute to altered reward discounting behavior in non-obese and obese individuals. These results raise interesting questions about whether and how striatal D2 receptor binding and metabolic factors, including β-cell function, interact to affect reward discounting in humans.

Emotional Eating Phenotype is Associated with Central Dopamine D2 Receptor Binding Independent of Body Mass Index

PET studies have provided mixed evidence regarding central D2/D3 dopamine receptor binding and its relationship with obesity as measured by body mass index (BMI). Other aspects of obesity may be more tightly coupled to the dopaminergic system. We characterized obesity-associated behaviors and determined if these related to central D2 receptor (D2R) specific binding independent of BMI. Twenty-two obese and 17 normal-weight participants completed eating- and reward-related questionnaires and underwent PET scans using the D2R-selective and nondisplaceable radioligand (N-[¹¹C]methyl)benperidol. Questionnaires were grouped by domain (eating related to emotion, eating related to reward, non-eating behavior motivated by reward or sensitivity to punishment). Normalized, summed scores for each domain were compared between obese and normal-weight groups and correlated with striatal and midbrain D2R binding. Compared to normal-weight individuals, the obese group self-reported higher rates of eating related to both emotion and reward (p < 0.001), greater sensitivity to punishment (p = 0.06), and lower non-food reward behavior (p < 0.01). Across normal-weight and obese participants, self-reported emotional eating and non-food reward behavior positively correlated with striatal (p < 0.05) and midbrain (p < 0.05) D2R binding, respectively. In conclusion, an emotional eating phenotype may reflect altered central D2R function better than other commonly used obesity-related measures such as BMI.

Current considerations regarding food addiction

"Food addiction" is an emerging area, and behavioral and biological overlaps have been observed between eating and addictive disorders. Potential misconceptions about applying an addiction framework to problematic eating behavior may inhibit scientific progress. Critiques of "food addiction" that focus on descriptive differences between overeating and illicit drugs are similar to early criticisms of the addictiveness of tobacco. Although food is necessary for survival, the highly processed foods associated with addictive-like eating may provide little health benefit. Individual differences are important in determining who develops an addiction. If certain foods are addictive, the identification of possible risk factors for "food addiction" is an important next step. Not all treatments for addiction require abstinence. Addiction interventions that focus on moderation or controlled use may lead to novel approaches to treating eating-related problems. Finally, addiction-related policies that focus on environmental (instead of educational) targets may have a larger public health impact in reducing overeating.

Food addiction in overweight and obese adolescents seeking weight-loss treatment

Some forms of overeating closely resemble addictive behaviour. The Yale Food Addiction Scale (YFAS) was developed to measure such addiction-like eating in humans and has been employed in numerous studies for examining food addiction in adults. Yet, little is known about food addiction in children and adolescents. Fifty adolescents were recruited at the beginning of treatment in a weight-loss hospital and completed the YFAS among other questionnaires. Nineteen participants (38%) received a YFAS diagnosis, who did not differ in age, body mass and gender distribution from those not receiving a diagnosis. However, those with food addiction reported more binge days, more frequent food cravings, higher eating, weight and shape concerns, more symptoms of depression and higher attentional and motor impulsivity. Eating restraint and nonplanning impulsivity did not differ between groups. Results replicate findings from studies in obese adults such that food addiction is not related to age, gender, body mass or eating restraint, but to higher eating pathology, more symptoms of depression and higher impulsivity. Furthermore, results highlight that particularly attentional impulsivity is related to 'food addiction'. Addiction-like eating appears to be a valid phenotype in a substantial subset of treatment-seeking, obese adolescents.

Food and addiction among the ageing population

Obesity among the elderly is a growing public health concern. Among the various factors that may contribute to the current rates of obesity is the rewarding aspect of highly palatable foods and beverages, which may lead to overconsumption and excess caloric intake. The present review describes recent research supporting the hypothesis that, for some individuals, the consumption these highly palatable foods and beverages may lead to the development of addictive-like behaviors. In particular, the authors consider the relevance of this hypothesis to the ageing population.

Which foods may be addictive? The roles of processing, fat content, and glycemic load

Objectives

We propose that highly processed foods share pharmacokinetic properties (e.g. concentrated dose, rapid rate of absorption) with drugs of abuse, due to the addition of fat and/or refined carbohydrates and the rapid rate the refined carbohydrates are absorbed into the system, indicated by glycemic load (GL). The current study provides preliminary evidence for the foods and food attributes implicated in addictive-like eating.

Design

Cross-sectional.

Setting

University (Study One) and community (Study Two).

Participants

120 undergraduates participated in Study One and 384 participants recruited through Amazon MTurk participated in Study Two.

Measurements

In Study One, participants (n = 120) completed the Yale Food Addiction Scale (YFAS) followed by a forced-choice task to indicate which foods, out of 35 foods varying in nutritional composition, were most associated with addictive-like eating behaviors. Using the same 35 foods, Study Two utilized hierarchical linear modeling to investigate which food attributes (e.g., fat grams) were related to addictive-like eating behavior (at level one) and explored the influence of individual differences for this association (at level two).

Results

In Study One, processed foods, higher in fat and GL, were most frequently associated with addictive-like eating behaviors. In Study Two, processing was a large, positive predictor for whether a food was associated with problematic, addictive-like eating behaviors. BMI and YFAS symptom count were small-to-moderate, positive predictors for this association. In a separate model, fat and GL were large, positive predictors of problematic food ratings. YFAS symptom count was a small, positive predictor of the relationship between GL and food ratings.

Conclusion

The current study provides preliminary evidence that not all foods are equally implicated in addictive-like eating behavior, and highly processed foods, which may share characteristics with drugs of abuse (e.g. high dose, rapid rate of absorption) appear to be particularly associated with “food addiction.”

Relation of the multilocus genetic composite reflecting high dopamine signaling capacity to future increases in BMI

Because food intake exerts its rewarding effect by increasing dopamine (DA) signaling in reward circuitry, it theoretically follows that individuals with a greater number of genotypes putatively associated with high DA signaling capacity are at increased risk for overeating and subsequent weight gain. We tested the association between the multilocus genetic composite risk score, defined by the total number of genotypes putatively associated with greater DA signaling capacity (i.e. TaqIA A2 allele, DRD2-141C Ins/Del and Del/Del genotypes, DRD4-S allele, DAT1-S allele, and COMT Val/Val genotype), and future increases in Body Mass Index (BMI) in three prospective studies. Participants in Study 1 (N = 30; M age = 15.2; M baseline BMI = 26.9), Study 2 (N = 34; M age = 20.9; M baseline BMI = 28.2), and Study 3 (N = 162; M age = 15.3, M baseline BMI = 20.8) provided saliva samples from which epithelial cells were collected, permitting DNA extraction. The multilocus genetic composite risk score was associated with future increases in BMI in all three studies (Study 1, r = 0.37; Study 2, r = 0.22; Study 3, r = 0.14) and the overall sample (r = 0.19). DRD4-S was associated with increases in BMI in Study 1 (r = 0.42), Study 2 (r = 0.27), and in the overall sample (r = 0.17). DAT1-S was associated with increases in BMI in Study 3 (r = 0.17) and in the overall sample (r = 0.12). There were no associations between the other genotypes (TaqIA, COMT, and DRD2-141C) and change in BMI over 2-year follow-up. Data suggest that individuals with a genetic propensity for greater DA signaling capacity are at risk for future weight gain and that combining alleles that theoretically have a similar function may provide a more reliable method of modeling genetic risk associated with future weight gain than individual genotypes.

The prevalence of food addiction as assessed by the Yale Food Addiction Scale: a systematic review

Obesity is a global issue and it has been suggested that an addiction to certain foods could be a factor contributing to overeating and subsequent obesity. Only one tool, the Yale Food Addiction Scale (YFAS) has been developed to specifically assess food addiction. This review aimed to determine the prevalence of food addiction diagnosis and symptom scores, as assessed by the YFAS. Published studies to July 2014 were included if they reported the YFAS diagnosis or symptom score and were published in the English language. Twenty-five studies were identified including a total of 196,211 predominantly female, overweight/obese participants (60%). Using meta-analysis, the weighted mean prevalence of YFAS food addiction diagnosis was 19.9%. Food addiction (FA) diagnosis was found to be higher in adults aged >35 years, females, and overweight/obese participants. Additionally, YFAS diagnosis and symptom score was higher in clinical samples compared to non-clinical counterparts. YFAS outcomes were related to a range of other eating behavior measures and anthropometrics. Further research is required to explore YFAS outcomes across a broader spectrum of ages, other types of eating disorders and in conjunction with weight loss interventions to confirm the efficacy of the tool to assess for the presence of FA.

A psycho-genetic study of hedonic responsiveness in relation to "food addiction"

While food addiction has no formally-recognized definition, it is typically operationalized according to the diagnostic principles established by the Yale Food Addiction Scale-an inventory based on the symptom criteria for substance dependence in the DSM-IV. Currently, there is little biologically-based research investigating the risk factors for food addiction. What does exist has focused almost exclusively on dopaminergic reward pathways in the brain. While brain opioid signaling has also been strongly implicated in the control of food intake, there is no research examining this neural circuitry in the association with food addiction. The purpose of the study was therefore to test a model predicting that a stronger activation potential of opioid circuitry-as indicated by the functional A118G marker of the mu-opioid receptor gene-would serve as an indirect risk factor for food addiction via a heightened hedonic responsiveness to palatable food. Results confirmed these relationships. In addition, our findings that the food-addiction group had significantly higher levels of hedonic responsiveness to food suggests that this bio-behavioral trait may foster a proneness to overeating, to episodes of binge eating, and ultimately to a compulsive and addictive pattern of food intake.

Food addiction in the light of DSM-5

The idea that specific kind of foods may have an addiction potential and that some forms of overeating may represent an addicted behavior has been discussed for decades. In recent years, the interest in food addiction is growing and research on this topic lead to more precise definitions and assessment methods. For example, the Yale Food Addiction Scale has been developed for the measurement of addiction-like eating behavior based on the diagnostic criteria for substance dependence of the fourth revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). In 2013, diagnostic criteria for substance abuse and-dependence were merged, thereby increasing the number of symptoms for substance use disorders (SUDs) in the DSM-5. Moreover, gambling disorder is now included along SUDs as a behavioral addiction. Although a plethora of review articles exist that discuss the applicability of the DSM-IV substance dependence criteria to eating behavior, the transferability of the newly added criteria to eating is unknown. Thus, the current article discusses if and how these new criteria may be translated to overeating. Furthermore, it is examined if the new SUD criteria will impact future research on food addiction, for example, if "diagnosing" food addiction should also be adapted by considering all of the new symptoms. Given the critical response to the revisions in DSM-5, we also discuss if the recent approach of Research Domain Criteria can be helpful in evaluating the concept of food addiction.

Hormonal and neural mechanisms of food reward, eating behaviour and obesity

With rising rates of obesity, research continues to explore the contributions of homeostatic and hedonic mechanisms related to eating behaviour. In this Review, we synthesize the existing information on select biological mechanisms associated with reward-related food intake, dealing primarily with consumption of highly palatable foods. In addition to their established functions in normal feeding, three primary peripheral hormones (leptin, ghrelin and insulin) play important parts in food reward. Studies in laboratory animals and humans also show relationships between hyperphagia or obesity and neural pathways involved in reward. These findings have prompted questions regarding the possibility of addictive-like aspects in food consumption. Further exploration of this topic may help to explain aberrant eating patterns, such as binge eating, and provide insight into the current rates of overweight and obesity.

Correlates of food addiction in obese individuals seeking bariatric surgery

Recent evidence suggests that palatable, high-calorie foods may have an addictive potential. Accordingly, obesity and overconsumption of such foods have been associated with addiction-like eating behaviour. The present study investigated whether individuals with obesity can be classified as food-addicted and which factors would differentiate between food-addicted and non-addicted individuals. We administered the German version of the Yale Food Addiction Scale and other questionnaires to obese individuals seeking bariatric surgery (N = 96). Results showed that 40% of the sample could be diagnosed as food-addicted. Food-addicted individuals reported more frequent food cravings, higher eating disorder psychopathology and more depressive symptoms than the non-addicted group. Age, body mass and gender distribution did not differ between groups. The food addiction group had higher attentional but similar motor and non-planning impulsivity, and had lower scores on the Alcohol Use Disorders Identification Test (AUDIT) compared with the non-addicted group. Scores on the AUDIT were associated with impulsivity in the non-addicted group only. We conclude that the prevalence of food addiction is higher in candidates for bariatric surgery compared with the general population and obese individuals not seeking bariatric surgery. A diagnosis of food addiction is associated with higher eating pathology and depression. Moreover, only attentional impulsivity, but not other dimensions of impulsivity, is associated with addictive eating. Finally, food addiction and impulsivity interactively predicted alcohol use, suggesting a crucial role of psychological variables and eating style in determining alcohol consumption in pre-bariatric patients, independent of body mass.

Sex differences in addictive disorders

Gender-dependent differences in the rate of initiation and frequency of misuse of addicting drugs have been widely described. Yet, men and women also differ in their propensity to become addicted to other rewarding stimuli (e.g., sex, food) or activities (e.g., gambling, exercising). The goal of the present review is to summarize current evidence for gender differences not only in drug addiction, but also in other forms of addictive behaviours. Thus, we first reviewed studies showing gender-dependent differences in drug addiction, food addiction, compulsive sexual activity, pathological gambling, Internet addiction and physical exercise addiction. Potential risk factors and underlying brain mechanisms are also examined, with particular emphasis given to the role of sex hormones in modulating addictive behaviours. Investigations on factors allowing the pursuit of non-drug rewards to become pathological in men and women are crucial for designing gender-appropriate treatments of both substance and non-substance addictions.

The association of "food addiction" with disordered eating and body mass index

INTRODUCTION

The contribution of an addictive process to elevated body mass index (BMI) and disordered eating is an area of growing interest. Yet, little is known about how "food addiction" may be related to disordered eating and obesity. The ability of addictive-like eating to account for eating pathology not captured by traditional eating disorders is unknown. No prior research has examined the association of "food addiction" with bulimia nervosa (BN). Finally, little is understood about the association of "food addiction" with patterns of dieting and weight gain. The current study was conducted to address these gaps in the literature.

MATERIAL AND METHODS

Participants (N=815) were recruited from online advertisements nationwide and completed measures related to "food addiction", BMI, weight history, and disordered eating.

RESULTS

Addictive-like eating was associated with elevated current and lifetime highest BMI, weight cycling, and eating pathology. The prevalence of "food addiction" was higher in participants with BN than in those with binge eating disorder (BED). "Food addiction" continued to be related to clinically relevant variables, especially elevated BMI, even when participants did not meet criteria for BED or BN. The co-occurrence of "food addiction" with eating disorders appears to be associated with a more severe variant of eating pathology.

DISCUSSION

An addictive-type response to highly palatable food may be contributing to eating-related problems, including obesity and eating disorders. BN relative to BED appears to be more strongly associated with "food addiction." Additionally, the concept of "food addiction" appears to capture clinically relevant information in participants who do not meet criteria for either BN or BED. Further examination of "food addiction" may be important in understanding the mechanisms underlying certain types of problematic eating behavior.

Food cravings, appetite, and snack-food consumption in response to a psychomotor stimulant drug: the moderating effect of "food-addiction"

There is mounting evidence that many highly processed foods have addictive properties, and that some cases of compulsive overeating resemble an addiction disorder. While support for the Yale Food Addiction Scale (YFAS) as a valid diagnostic tool has been impressive and continues to increase, to date, no research has examined the food-addiction construct in response to an actual food stimulus, and in relation to direct measures of appetite and food consumption. As part of a larger community-based study of overeating in healthy adults who were predominately overweight and obese (aged 25-50 years), 136 participants completed the YFAS, of whom 23 met the diagnostic criteria for food-addiction. They took part in a 2-day, double-blind, cross-over, single-dose drug challenge using a psychomotor stimulant (methylphenidate) and placebo. Participants were first assessed on ratings of appetite and food cravings after holding and tasting their favorite snack food, after which they were able to eat all or part of the snack, as they wished. Three separate repeated-measures analysis-of-variance procedures were carried out, each with two between-subjects factors (Diagnosis: food-addiction vs. non-food addiction) and (Sex: male vs. female) and 1 within-subjects factor (Days: drug vs. placebo). As anticipated, for all three dependent variables, there was a significant main effect for Days with a response decrease from placebo to the drug condition. With respect to food cravings and appetite ratings, results indicated that the food addiction group had significantly higher scores on both variables. For food consumption, there was a significant Days × Diagnosis interaction whereby the food-addiction group showed no food-intake suppression across days compared to the non-food-addiction group who demonstrated a significant decrease in snack-food consumption with methylphenidate. The finding that the food-addiction group was resistant to the food-intake suppression typically induced by a dopamine agonist supports evidence of dopamine signaling-strength differences in individuals with compulsive overeating compared to those without this disorder. This represents the first demonstration that individuals defined by their food-addiction status have a unique pattern of food-intake following a pharmacologic challenge with such agents.

Loss of control over eating: a description of the eating disorder/obesity spectrum in women

GOALS

This study aimed to analyse the association, commonalities and differences between obesity and eating disorders (ED).

METHOD

A total of 150 female patients [50 obese with bulimia nervosa (OB + BN), 50 obese with binge eating disorders (OB + BED), 50 obese without eating disorders (OB)] and 50 female healthy-eating/weight control (CG) volunteers participated in this study.

ASSESSMENT

All participants were assessed by the Eating Disorders Inventory-2 (EDI-2), the Symptom Checklist-Revised (SCL-90-R) and the Temperament and Character Inventory-Revised.

RESULTS

In general, all the groups differed significantly and showed linear trends (OB + BN > OB + BED > OB > CG) on general and eating psychopathology (SCL-90-R and EDI-2). Regarding personality traits, statistically significant differences across all four groups were found on Harm Avoidance and Self-Directedness. Whereas some symptoms were shared in extreme weight conditions, others were specifically related to ED.

CONCLUSIONS

The presence of binge and purge symptomatology in obese patients is clinically relevant. These findings help to understand the relationship between Obesity and ED.