Obesity and the brain: how convincing is the addiction model?

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.

Interrelationships among impulsive personality traits, food addiction, and Body Mass Index

OBJECTIVE

Impulsive personality traits have been robustly associated with alcohol and drug misuse, but have received little attention in the context of food addiction. The goal of the current study was to examine the interrelationships between impulsive personality traits, food addiction, and Body Mass Index (BMI), including indirect pathways of influence.

METHOD

Participants (N = 233) completed the Yale Food Addiction Scale (YFAS) to assess patterns of addictive consumption of food, the upps-p impulsivity scale to assess impulsive personality traits, and provided weight and height to generate BMI.

RESULTS

Significant positive associations were found between facets of impulsivity, food addiction symptoms, and BMI. Impulsivity was found to be indirectly associated with BMI by way of associations with addictive consumption of food. In particular, an inclination toward behaving irrationally while experiencing negative mood states (Negative Urgency) and low levels of task persistence (lack of Perseverance) were significantly associated with food addiction directly and that relationship was responsible for their relationship to BMI.

CONCLUSIONS

Dispositional impulsivity, routinely associated with high-risk behaviors including addictive consumption of alcohol and drugs, may be an important risk factor when considering tendency to engage in addictive consumption of food. Monitoring food addiction symptoms early may help reduce the likelihood that compulsive food consumption patterns result in weight gain and obesity. Methodological considerations are discussed.

Obese patients after gastric bypass surgery have lower brain-hedonic responses to food than after gastric banding

OBJECTIVES

Roux-en-Y gastric bypass (RYGB) has greater efficacy for weight loss in obese patients than gastric banding (BAND) surgery. We hypothesise that this may result from different effects on food hedonics via physiological changes secondary to distinct gut anatomy manipulations.

DESIGN

We used functional MRI, eating behaviour and hormonal phenotyping to compare body mass index (BMI)-matched unoperated controls and patients after RYGB and BAND surgery for obesity.

RESULTS

Obese patients after RYGB had lower brain-hedonic responses to food than patients after BAND surgery. RYGB patients had lower activation than BAND patients in brain reward systems, particularly to high-calorie foods, including the orbitofrontal cortex, amygdala, caudate nucleus, nucleus accumbens and hippocampus. This was associated with lower palatability and appeal of high-calorie foods and healthier eating behaviour, including less fat intake, in RYGB compared with BAND patients and/or BMI-matched unoperated controls. These differences were not explicable by differences in hunger or psychological traits between the surgical groups, but anorexigenic plasma gut hormones (GLP-1 and PYY), plasma bile acids and symptoms of dumping syndrome were increased in RYGB patients.

CONCLUSIONS

The identification of these differences in food hedonic responses as a result of altered gut anatomy/physiology provides a novel explanation for the more favourable long-term weight loss seen after RYGB than after BAND surgery, highlighting the importance of the gut-brain axis in the control of reward-based eating behaviour.

Ghrelin mimics fasting to enhance human hedonic, orbitofrontal cortex, and hippocampal responses to food

BACKGROUND

Ghrelin, which is a stomach-derived hormone, increases with fasting and energy restriction and may influence eating behaviors through brain hedonic reward-cognitive systems. Therefore, changes in plasma ghrelin might mediate counter-regulatory responses to a negative energy balance through changes in food hedonics.

OBJECTIVE

We investigated whether ghrelin administration (exogenous hyperghrelinemia) mimics effects of fasting (endogenous hyperghrelinemia) on the hedonic response and activation of brain-reward systems to food.

DESIGN

In a crossover design, 22 healthy, nonobese adults (17 men) underwent a functional magnetic resonance imaging (fMRI) food-picture evaluation task after a 16-h overnight fast (Fasted-Saline) or after eating breakfast 95 min before scanning (730 kcal, 14% protein, 31% fat, and 55% carbohydrate) and receiving a saline (Fed-Saline) or acyl ghrelin (Fed-Ghrelin) subcutaneous injection before scanning. One male subject was excluded from the fMRI analysis because of excess head motion, which left 21 subjects with brain-activation data.

RESULTS

Compared with the Fed-Saline visit, both ghrelin administration to fed subjects (Fed-Ghrelin) and fasting (Fasted-Saline) significantly increased the appeal of high-energy foods and associated orbitofrontal cortex activation. Both fasting and ghrelin administration also increased hippocampus activation to high-energy- and low-energy-food pictures. These similar effects of endogenous and exogenous hyperghrelinemia were not explicable by consistent changes in glucose, insulin, peptide YY, and glucagon-like peptide-1. Neither ghrelin administration nor fasting had any significant effect on nucleus accumbens, caudate, anterior insula, or amygdala activation during the food-evaluation task or on auditory, motor, or visual cortex activation during a control task.

CONCLUSIONS

Ghrelin administration and fasting have similar acute stimulatory effects on hedonic responses and the activation of corticolimbic reward-cognitive systems during food evaluations. Similar effects of recurrent or chronic hyperghrelinemia on an anticipatory food reward may contribute to the negative impact of skipping breakfast on dietary habits and body weight and the long-term failure of energy restriction for weight loss.

Overlap of food addiction and substance use disorders definitions: analysis of animal and human studies

Food has both homeostatic and hedonic components, which makes it a potent natural reward. Food related reward could therefore promote an escalation of intake and trigger symptoms associated to withdrawal, suggesting a behavioral parallel with substance abuse. Animal and human theoretical models of food reward and addiction have emerged, raising further interrogations on the validity of a bond between Substance Use Disorders, as clinically categorized in the DSM 5, and food reward. These models propose that highly palatable food items, rich in sugar and/or fat, are overly stimulating to the brain's reward pathways. Moreover, studies have also investigated the possibility of causal link between food reward and the contemporary obesity epidemic, with obesity being potentiated and maintained due to this overwhelming food reward. Although natural rewards are a hot topic in the definition and categorization of Substance Use Disorders, proofs of concept and definite evidence are still inconclusive. This review focuses on available results from experimental studies in animal and human models exploring the concept of food addiction, in an effort to determine if it depicts a specific phenotype and if there is truly a neurobiological similarity between food addiction and Substance Use Disorders. It describes results from sugar, fat and sweet-fat bingeing in rodent models, and behavioral and neurobiological assessments in different human populations. Although pieces of behavioral and neurobiological evidence supporting a food addiction phenotype in animals and humans are interesting, it seems premature to conclude on its validity.

Binge-like consumption of a palatable food accelerates habitual control of behavior and is dependent on activation of the dorsolateral striatum

Access to highly palatable and calorically dense foods contributes to increasing rates of obesity worldwide. Some have made the controversial argument that consumption of such foods can lead to "food addiction," yet little is known about how long-term access to highly palatable foods might alter goal-directed learning and decision making. In the following experiments, rats were given 5 weeks of continuous or restricted daily access to sweetened condensed milk (SCM) before instrumental training for food reward. Subsequently we examined whether goal-directed performance was impaired in these groups using the outcome-devaluation task. Control rats reduced responding following devaluation of the earned outcome as did those with previous continuous access to SCM. Of interest, rats with previous restricted access to SCM responded similarly under the devalued and nondevalued conditions, indicating loss of goal-directed control of responding. To identify whether the loss of goal-directed control was accompanied by differences in neuronal activity, we used c-Fos immunohistochemistry to examine the patterns of activation during devaluation testing. We observed greater c-Fos immunoreactivity in the dorsolateral striatum (DLS) and associated cortical regions in the group that received previous restricted access to SCM and demonstrated a lack of sensitivity to outcome devaluation. Infusion of the AMPA-receptor antagonist CNQX or dopamine D1-receptor antagonist SCH-23390 into the DLS before testing restored goal-directed performance in the restricted SCM group, confirming that this region is essential for habit-based performance. These results indicate that previous diet can alter subsequent learning and activity in the neural circuits that support performance.

Dorsal striatal dopamine, food preference and health perception in humans

To date, few studies have explored the neurochemical mechanisms supporting individual differences in food preference in humans. Here we investigate how dorsal striatal dopamine, as measured by the positron emission tomography (PET) tracer [¹⁸F]fluorometatyrosine (FMT), correlates with food-related decision-making, as well as body mass index (BMI) in 16 healthy-weight to moderately obese individuals. We find that lower PET FMT dopamine synthesis binding potential correlates with higher BMI, greater preference for perceived “healthy” foods, but also greater healthiness ratings for food items. These findings further substantiate the role of dorsal striatal dopamine in food-related behaviors and shed light on the complexity of individual differences in food preference.

Cognitive and behavioural effects of sugar consumption in rodents. A review

The pronounced global rise in sugar consumption in recent years has been driven largely by increased consumption of sugar-sweetened beverages. Although high sugar intakes are recognised to increase the risk of obesity and related metabolic disturbances, less is known about how sugar might also impair cognition and learned behaviour. This review considers the effects of sugar in rodents on measures of learning and memory, reward processing, anxiety and mood. The parallels between sugar consumption and addictive behaviours are also discussed. The available evidence clearly indicates that sugar consumption can induce cognitive dysfunction. Deficits have been found most consistently on tasks measuring spatial learning and memory. Younger animals appear to be particularly sensitive to the effects of sugar on reward processing, yet results vary according to what reward-related behaviour is assessed. Sugar does not appear to produce long-term effects on anxiety or mood. Importantly, cognitive impairments have been found when intake approximates levels of sugar consumption in people and without changes to weight gain. There remain several caveats when extrapolating from animal models to putative effects of sugar on cognitive function in people. These issues are discussed in conjunction with potential underlying neural mechanisms and directions for future research.

Pavlovian conditioning and cross-sensitization studies raise challenges to the hypothesis that overeating is an addictive behavior

Elevated glucocorticoid levels and sign tracking (ST) in Pavlovian conditioning are potential biomarkers of compulsive behaviors such as addiction. As overeating is sometimes viewed as a form of addictive behavior, we hypothesized that murine Pavlovian sign trackers would have a greater propensity to overeat and develop obesity. Using a food reward in the classical conditioning paradigm, we show that ST behavior is a robust conditioned response but not a predictor of eating and growth trajectories in mice, thus challenging the view that the development of obesity and drug addiction depend on identical mechanisms. This interpretation was supported by experiments which showed that overweight mice do not display cross-sensitization to an addictive drug (morphine), and conversely, that overweight morphine-sensitized animals do not overconsume a highly rewarding food. Although the rewarding/motivational effects of both food and drugs of abuse are mediated by similar neurochemical mechanisms, obesity and drug addiction represent a summation of other dysfunctional input and output pathways that lead to the emergence of two distinct disorders, each of which would deserve a specific pharmacotherapeutic approach.

Food addiction as a causal model of obesity. Effects on stigma, blame, and perceived psychopathology

The present study examined the impact of the food-addiction model of obesity on weight stigma directed at obese people. Participants (n = 625) were randomly assigned to four experimental conditions. They were asked to read either a food-addiction explanatory model of obesity or a nonaddiction model, and subsequently read a vignette describing a target person who met the characteristics of one of these models and was either obese or of normal weight. Questionnaires assessed participants' stigmatization and blame of targets and their attribution of psychopathology toward targets. Additional questionnaires assessed stigma and blame directed toward obese people generally, and personal fear of fat. A manipulation check revealed that the food-addiction experimental condition did significantly increase belief in the food-addiction model. Significant main effects for addiction showed that the food-addiction model produced less stigma, less blame, and lower perceived psychopathology attributed to the target described in vignettes, regardless of the target's weight. The food-addiction model also produced less blame toward obese people in general and less fear of fat. The present findings suggest that presenting obesity as an addiction does not increase weight bias and could even be helpful in reducing the widespread prejudice against obese people.

Where is the comfort in comfort foods? Mechanisms linking fat signaling, reward, and emotion

BACKGROUND

Food in general, and fatty foods in particular, have obtained intrinsic reward value throughout evolution. This reward value results from an interaction between exteroceptive signals from different sensory modalities, interoceptive hunger/satiety signals from the gastrointestinal tract to the brain, as well as ongoing affective and cognitive processes. Further evidence linking food to emotions stems from folk psychology ('comfort foods') and epidemiological studies demonstrating high comorbidity rates between disorders of food intake, including obesity, and mood disorders such as depression.

PURPOSE

This review paper aims to give an overview of current knowledge on the neurophysiological mechanisms underlying the link between (fatty) foods, their reward value, and emotional responses to (anticipation of) their intake in humans. Firstly, the influence of exteroceptive sensory signals, including visual, olfactory ('anticipatory food reward'), and gustatory ('consummatory food reward'), on the encoding of reward value in the (ventral) striatum and of subjective pleasantness in the cingulate and orbitofrontal cortex will be discussed. Differences in these pathways and mechanisms between lean and obese subjects will be highlighted. Secondly, recent studies elucidating the mechanisms of purely interoceptive fatty acid-induced signaling from the gastrointestinal tract to the brain, including the role of gut peptides, will be presented. These studies have demonstrated that such subliminal interoceptive stimuli may impact on hedonic circuits in the brain, and thereby influence the subjective and neural responses to negative emotion induction. This suggests that the effect of foods on mood may even occur independently from their exteroceptive sensory properties.

New developments in human neurocognition: clinical, genetic, and brain imaging correlates of impulsivity and compulsivity

Impulsivity and compulsivity represent useful conceptualizations that involve dissociable cognitive functions, which are mediated by neuroanatomically and neurochemically distinct components of cortico-subcortical circuitry. The constructs were historically viewed as diametrically opposed, with impulsivity being associated with risk-seeking and compulsivity with harm-avoidance. However, they are increasingly recognized to be linked by shared neuropsychological mechanisms involving dysfunctional inhibition of thoughts and behaviors. In this article, we selectively review new developments in the investigation of the neurocognition of impulsivity and compulsivity in humans, in order to advance our understanding of the pathophysiology of impulsive, compulsive, and addictive disorders and indicate new directions for research.

Measuring "waiting" impulsivity in substance addictions and binge eating disorder in a novel analogue of rodent serial reaction time task

BACKGROUND

Premature responding is a form of motor impulsivity that preclinical evidence has shown to predict compulsive drug seeking but has not yet been studied in humans. We developed a novel translation of the task, based on the rodent 5-choice serial reaction time task, testing premature responding in disorders of drug and natural food rewards.

METHODS

Abstinent alcohol- (n = 30) and methamphetamine-dependent (n = 23) subjects, recreational cannabis users (n = 30), and obese subjects with (n = 30) and without (n = 30) binge eating disorder (BED) were compared with matched healthy volunteers and tested on the premature responding task.

RESULTS

Compared with healthy volunteers, alcohol- and methamphetamine-dependent subjects and cannabis users showed greater premature responding with no differences observed in obese subjects with or without BED. Current smokers exhibited greater premature responding versus ex-smokers and nonsmokers. Alcohol-dependent subjects also had lower motivation for explicit monetary incentives. A Motivation Index correlated negatively with alcohol use and binge eating severity.

CONCLUSIONS

Premature responding on a novel translation of a serial reaction time task was more evident in substance use disorders but not in obese subjects with or without BED. Lower motivation for monetary incentives linked alcohol use and binge eating severity. Our findings add to understanding the relationship between drug and natural food rewards.

Startling sweet temptations: hedonic chocolate deprivation modulates experience, eating behavior, and eyeblink startle

Many individuals restrict their food intake to prevent weight gain. This restriction has both homeostatic and hedonic effects but their relative contribution is currently unclear. To isolate hedonic effects of food restriction, we exposed regular chocolate eaters to one week of chocolate deprivation but otherwise regular eating. Before and after this hedonic deprivation, participants viewed images of chocolate and images of high-calorie but non-chocolate containing foods, while experiential, behavioral and eyeblink startle responses were measured. Compared to satiety, hedonic deprivation triggered increased chocolate wanting, liking, and chocolate consumption but also feelings of frustration and startle potentiation during the intertrial intervals. Deprivation was further characterized by startle inhibition during both chocolate and food images relative to the intertrial intervals. Individuals who responded with frustration to the manipulation and those who scored high on a questionnaire of impulsivity showed more relative startle inhibition. The results reveal the profound effects of hedonic deprivation on experiential, behavioral and attentional/appetitive response systems and underscore the role of individual differences and state variables for startle modulation. Implications for dieting research and practice as well as for eating and weight disorders are discussed.

The role of self-efficacy, coping, and lapses in weight maintenance

PURPOSE

Successful weight maintenance after weight loss is exceedingly rare. The present study aimed to identify psychological predictors of lapses and weight maintenance.

METHODS

Self-efficacy, coping, and perceptions of lapses were examined as potential predictors of lapse frequency and weight maintenance (percentage weight loss maintained). Participants included 67 adults (85.3 % women) who had intentionally lost a mean of 16 % of their body weight and had stopped losing weight at least 6 months prior to data collection. Participants completed a 7-day lapse diary tracking the frequency and perceived severity of their dietary and activity lapses, along with questionnaires on self-efficacy, coping, and characteristics of their weight loss.

RESULTS

Participants had lost a mean of 13.9 kg, 20.4 months prior to data collection. More frequent lapsing was correlated with lower self-efficacy and greater perceived lapse severity. Lower percentage of weight loss maintained was correlated with lower self-efficacy, poorer coping, greater perceived lapse severity, and longer time since weight loss ended. “Regainers,” who maintained <90 % of their weight loss, had poorer self-efficacy, poorer coping, greater lapse frequency, and greater perceived lapse severity, than “maintainers,” who maintained at least 90 % of their weight loss.

CONCLUSIONS

The results suggest that self-efficacy, coping, and perceived lapse severity are significant predictors of weight maintenance, consistent with the relapse prevention model. The goals of improving self-efficacy and coping skills might be important additions to weight maintenance programs.

The overlap between binge eating disorder and substance use disorders: Diagnosis and neurobiology

BACKGROUND AND AIMS

Binge eating disorder (BED) is a relatively common condition, especially in young adult females, and is characterized by chronic over-consumption of food resulting in embarrassment, distress, and potential health problems. It is formally included as a disorder in DSM-5 for the first time, an acknowledgement to its debilitating nature. This article explores the overlap between binge eating disorder and substance use disorders (SUD).

METHODS

The bibliographic search was a computerized screen of PubMed databases from January 1990 to the present. Binge eating disorder, substance use disorder, binging, obesity, food addiction, comorbidity, dopamine, opioid, serotonin, glutamate, and pharmacological treatment were the keywords used in searching.

RESULTS

BED shares similar phenomenology to SUD, including significant urges to engage in binging episodes, resulting in distress and impairment. Similar neurobiological pathways are found in both BED and SUD and medications based on similar neurobiology have been examined for both disorders. A subset of individuals with BED may have a "food addiction", but there is no clinical agreement on the meaning of "food addiction". Exploring the relationship between BED and obesity may also shed light on the extent to which BED can be viewed as an addiction.

CONCLUSIONS

Overall, nascent research regarding BED and SUD suggests an overlap between these disorders, but there are discrepancies between these two disorders that need further exploration.

Frontal cortical thinning and subcortical volume reductions in early adulthood obesity

Obesity depends on homeostatic and hedonic food intake behavior, mediated by brain plasticity changes in cortical and subcortical structures. The aim of this study was to investigate cortical thickness and subcortical volumes of regions related to food intake behavior in a healthy young adult sample with obesity. Thirty-seven volunteers, 19 with obesity (age=33.7±5.7 (20-39) years body-mass index (BMI)=36.08±5.92 (30.10-49.69)kg/m(2)) and 18 controls (age=32.3±5.9 (21-40) years; BMI=22.54±1.94 (19.53-24.97)kg/m(2)) participated in the study. Patients with neuropsychiatric or biomedical disorders were excluded. We used FreeSurfer software to analyze structural magnetic resonance images (MRI) and obtain global brain measures, cortical thickness and subcortical volume estimations. Finally, correlation analyses were performed for brain structure data and obesity measures. There were no between-group differences in age, gender, intelligence or education. Results showed cortical thickness reductions in obesity in the left superior frontal and right medial orbitofrontal cortex. In addition, the obesity group had lower ventral diencephalon and brainstem volumes than controls, while there were no differences in any other subcortical structure. There were no statistically significant correlations between brain structure and obesity measures. Overall, our work provides evidence of the structural brain characteristics associated with metabolically normal obesity. We found reductions in cortical thickness, ventral diencephalon and brainstem volumes in areas that have been implicated in food intake behavior.

A new biomarker of hedonic eating? A preliminary investigation of cortisol and nausea responses to acute opioid blockade

Overweight and obese individuals differ in their degree of hedonic eating. This may reflect adaptations in reward-related neural circuits, regulated in part by opioidergic activity. We examined an indirect, functional measure of central opioidergic activity by assessing cortisol and nausea responses to acute opioid blockade using the opioid antagonist naltrexone in overweight/obese women (mean BMI=31.1±4.8) prior to the start of a mindfulness-based intervention to reduce stress eating. In addition, we assessed indices of hedonic-related eating, including eating behaviors (binge eating, emotional eating, external eating, restraint) and intake of sweets/desserts and carbohydrates (Block Food Frequency); interoceptive awareness (which is associated with dysregulated eating behavior); and level of adiposity at baseline. Naltrexone-induced increases in cortisol were associated with greater emotional and restrained eating and lower interoceptive awareness. Naltrexone-induced nausea was associated with binge eating and higher adiposity. Furthermore, in a small exploratory analysis, naltrexone-induced nausea predicted treatment response to the mindfulness intervention, as participants with more severe nausea at baseline maintained weight whereas those with little or no nausea responses tended to gain weight. These preliminary data suggest that naltrexone-induced cortisol release and nausea may help identify individuals who have greater underlying food reward dependence, which leads to an excessive drive to eat. Future research is needed to confirm this finding and to test if these markers of opioidergic tone might help predict success in certain types of weight management programs.

Striatal ups and downs: their roles in vulnerability to addictions in humans

Susceptibility to addictive behaviors has been related to both increases and decreases in striatal function. Both profiles have been reported in humans as well as in animal models. Yet, the mechanisms underlying these opposing effects and the manner in which they relate to the behavioral development and expression of addiction remain unclear. In the present review of human studies, we describe a number of factors that could influence whether striatal hyper- or hypo-function is observed and propose a model that integrates the influence of these opposite responses on the expression of addiction related behaviors. Central to this model is the role played by the presence versus absence of addiction related cues and their ability to regulate responding to abused drugs and other rewards. Striatal function and incentive motivational states are increased in the presence of these cues and decreased in their absence. Alternations between these states might account for the progressive narrowing of interests as addictions develop and point to relevant processes to target in treatment.

The metabolic and endocrine response and health implications of consuming sugar-sweetened beverages: findings from recent randomized controlled trials

Fructose-containing sugars, including fructose itself, high fructose corn syrup (HFCS), and sucrose have engendered considerable controversy. The effects of HFCS and sucrose in sugar-sweetened beverages, in particular, have generated intense scientific debate that has spilled over to the public. This controversy is related to well-known differences in metabolism between fructose and glucose in the liver. In addition, research studies have often been conducted comparing pure fructose and pure glucose even though neither is consumed to any appreciable degree in isolation in the human diet. Other evidence has been drawn from animal studies and epidemiologic or cohort studies. Few randomized controlled trials (RCTs) have compared HFCS with sucrose (the 2 sugars most commonly consumed in the human diet) at dosage amounts within the normal human consumption range. This review compares results of recently concluded RCTs with other forms of evidence related to fructose, HFCS, and sucrose. We conclude that great caution must be used when suggesting adverse health effects of consuming these sugars in the normal way they are consumed and at the normal amounts in the human diet, because RCTs do not support adverse health consequences at these doses when employing these sugars.

Neuropsychological assessment as a predictor of weight loss in obese adolescents

BACKGROUND

Obese individuals are known to be more impulsive than their normal-weight counterparts. Impulsivity has been postulated to be a predictor of weight loss.

DESIGN

A pre-post study was designed to determine for the first time whether impulsivity changed with weight loss during a lifestyle and physical activity intervention programme lasting 2-8 weeks.

SUBJECTS

Fifty-three obese adolescents with a body mass index (BMI) of 33.75 ± 7.9 attending a residential camp were tested and compared at baseline with 50 non-obese adolescents with a mean BMI of 20.6 ± 2.3.

MEASUREMENTS

Inhibitory control was measured with the CANTAB (Cambridge Cognition, Cambridge, UK) Stop Signal Task. MATLAB (The Mathswork Inc., Natick, MA, USA) was used to measure the temporal discounting constant.

RESULTS

The obese group was more impulsive than the normal weight adolescents. BMI reduced significantly from 33.76 kg m(-2) to 30.93 kg m(-2) after completing camp. The stop signal reaction time (SSRT) decreased from 225.38 ± 94.22 to 173.76 ± 107.05 ms (n=47, P=0.0001). A reduction in inhibitory control during camp was predictive of those who showed the greatest reduction in BMI (Wilks' Lambda=0.9, F(1,50)=4.85, P=0.034). The number of weeks in camp (Wilks' Lambda=0.83, F(1,50)=9.826, P=0.003) and the age of the adolescents (Wilks' Lambda=0.87, F(1,50)=5.98, P=0.02) were significantly associated with a reduction in inhibitory control as measured by the SSRT. A longer stay in camp was associated with a greater reduction in SSRT (B=25.45, t=2.02, P=0.05). Increasing age had a significant moderating role in the reduction of inhibitory control (B=-0.3, t=-0.034, P=0.05). Temporal discounting for monetary reward also fell significantly during camp.

CONCLUSION

This study highlights the potential to identify those who are obese by using an easy-to-measure psychometric test. Furthermore, it is the first study to report a reduction in impulsivity and an improvement in well-being as part of a government-approved residential camp for obese adolescents. The potential mechanisms for change in impulsivity with weight are discussed.

Comparing the effects of food restriction and overeating on brain reward systems

Both caloric restriction and overeating have been shown to affect neural processes associated with reinforcement. Both preclinical and some clinical studies have provided evidence that food restriction may increase reward sensitivity, and while there are mixed findings regarding the effects of overeating on reward sensitivity, there is strong evidence linking this behavior with changes in reward-related brain regions. Evidence of these changes comes in part from findings that show that such eating patterns are associated with increased drug use. The data discussed here regarding the differential effects of various eating patterns on reward systems may be particularly relevant to the aging population, as this population has been shown to exhibit altered reward sensitivity and decreased caloric consumption. Moreover, members of this population appear to be increasingly affected by the current obesity epidemic. Food, like alcohol or drugs, can stimulate its own consumption and produce similar neurochemical changes in the brain. Age-related loss of appetite, decreased eating, and caloric restriction are hypothesized to be associated with changes in the prevalence of substance misuse, abuse, and dependence seen in this cohort.

Public views on food addiction and obesity: implications for policy and treatment

Background

According to their advocates, neurobiological explanations of overeating, or “food addiction”, have the potential to impact public understanding and treatment of obesity. In this study, we examine the public’s acceptance of the concept of food addiction as an explanation of overeating and assess its effects upon their attitudes toward obese persons and the treatment of obesity.

Methods and Findings

We conducted an online survey of 479 adults from the US (n = 215) and Australia (n = 264). There was substantial support for the idea of food addiction, particularly among obese participants. Over half favoured treating obesity as a type of addiction. Psychotherapy was believed to be the most effective treatment and educational and support programs were the preferred policies to address food addiction. There was very little support for increasing taxes on obesogenic foods. Despite the strong support for seeing obesity as a form of addiction, respondents still saw obesity as primarily the result of personal choices and emphasized the need for individuals to take responsibility for their eating.

Conclusions

Our sample of the general public strongly supported the idea of obesity as a form of food addiction; but this did not translate into support of clinical and public health policies that experts believe are most likely to reduce the prevalence of obesity. The reasons for the apparent disjunction between support for food addiction and a strong emphasis on personal choice for weight warrant further examination.

Low control over palatable food intake in rats is associated with habitual behavior and relapse vulnerability: individual differences

The worldwide obesity epidemic poses an enormous and growing threat to public health. However, the neurobehavioral mechanisms of overeating and obesity are incompletely understood. It has been proposed that addiction-like processes may underlie certain forms of obesity, in particular those associated with binge eating disorder. To investigate the role of addiction-like processes in obesity, we adapted a model of cocaine addiction-like behavior in rats responding for highly palatable food. Here, we tested whether rats responding for highly palatable chocolate Ensure would come to show three criteria of addiction-like behavior, i.e., high motivation, continued seeking despite signaled non-availability and persistence of seeking despite aversive consequences. We also investigated whether exposure to a binge model (a diet consisting of alternating periods of limited food access and access to highly palatable food), promotes the appearance of food addiction-like behavior. Our data show substantial individual differences in control over palatable food seeking and taking, but no distinct subgroup of animals showing addiction-like behavior could be identified. Instead, we observed a wide range extending from low to very high control over palatable food intake. Exposure to the binge model did not affect control over palatable food seeking and taking, however. Animals that showed low control over palatable food intake (i.e., scored high on the three criteria for addiction-like behavior) were less sensitive to devaluation of the food reward and more prone to food-induced reinstatement of extinguished responding, indicating that control over palatable food intake is associated with habitual food intake and vulnerability to relapse. In conclusion, we present an animal model to assess control over food seeking and taking. Since diminished control over food intake is a major factor in the development of obesity, understanding its behavioral and neural underpinnings may facilitate improved management of the obesity epidemic.

Food addiction: its prevalence and significant association with obesity in the general population

Background

‘Food addiction’ shares a similar neurobiological and behavioral framework with substance addiction. However whether, and to what degree, ‘food addiction’ contributes to obesity in the general population is unknown.

Objectives

to assess 1) the prevalence of ‘food addiction’ in the Newfoundland population; 2) if clinical symptom counts of ‘food addiction’ were significantly correlated with the body composition measurements; 3) if food addicts were significantly more obese than controls, and 4) if macronutrient intakes are associated with ‘food addiction’.

Design

A total of 652 adults (415 women, 237 men) recruited from the general population participated in this study. Obesity was evaluated by Body Mass Index (BMI) and Body Fat percentage measured by dual-energy X-ray absorptiometry. ‘Food addiction’ was assessed using the Yale Food Addiction Scale and macronutrient intake was determined from the Willet Food Frequency Questionnaire.

Results

The prevalence of ‘food addiction’ was 5.4% (6.7% in females and 3.0% in males) and increased with obesity status. The clinical symptom counts of ‘food addiction’ were positively correlated with all body composition measurements across the entire sample (p<0.001). Obesity measurements were significantly higher in food addicts than controls; Food addicts were 11.7 (kg) heavier, 4.6 BMI units higher, and had 8.2% more body fat and 8.5% more trunk fat. Furthermore, food addicts consumed more calories from fat and protein compared with controls.

Conclusion

Our results demonstrated that ‘food addiction’ contributes to severity of obesity and body composition measurements from normal weight to obese individuals in the general population with higher rate in women as compared to men.

Central nervous system biomarkers for antiobesity drug development

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Neuroimaging, cognitive and behavioural biomarkers can aid antiobesity drug development.

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These biomarkers can detect early signals of mechanistic efficacy and adverse effects.

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In Phase II biomarkers can provide proof-of-concept to inform the decision to advance to Phase III.

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Potential biomarker candidates that have been used with antiobesity drugs are discussed.

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These candidate biomarkers need further exploration, standardisation and validation.

With antiobesity agents, weight loss can emerge from an array of metabolic, cognitive and behavioural changes that translate into weight change over time. In early drug development, characterising these changes can actually be more informative than simply measuring weight loss. Biomarkers for these mechanisms can be used to determine whether potential compounds are worth developing further by providing proof of mechanistic action and detecting early signs of neuropsychiatric adverse effects. In this review, we examine potential biomarkers for effects on metabolism and satiety, hedonics and motivation, and eating behaviour. We also review biomarkers for early detection of neuropsychiatric adverse effects.

Food related processes in the insular cortex

The insular cortex is a multimodal brain region with regional cytoarchitectonic differences indicating various functional specializations. As a multisensory neural node, the insular cortex integrates perception, emotion, interoceptive awareness, cognition, and gustation. Regarding the latter, predominantly the anterior part of the insular cortex is regarded as the primary taste cortex. In this review, we will specifically focus on the involvement of the insula in food processing and on multimodal integration of food-related items. Influencing factors of insular activation elicited by various foods range from calorie-content to the internal physiologic state, body mass index or eating behavior. Sensory perception of food-related stimuli including seeing, smelling, and tasting elicits increased activation in the anterior and mid-dorsal part of the insular cortex. Apart from the pure sensory gustatory processing, there is also a strong association with the rewarding/hedonic aspects of food items, which is reflected in higher insular activity and stronger connections to other reward-related areas. Interestingly, the processing of food items has been found to elicit different insular activation in lean compared to obese subjects and in patients suffering from an eating disorder (anorexia nervosa (AN), bulimia nervosa (BN)). The knowledge of functional differences in the insular cortex opens up the opportunity for possible noninvasive treatment approaches for obesity and eating disorders. To target brain functions directly, real-time functional magnetic resonance imaging neurofeedback offers a state-of-the-art tool to learn to control the anterior insular cortex activity voluntarily. First evidence indicates that obese adults have an enhanced ability to regulate the anterior insular cortex.

Exploration of "food addiction" in overweight and obese treatment-seeking adults

There is growing interest in conceptualizing obesity as a "food addiction." The current study investigated the prevalence and correlates of "food addiction" (FA), as defined by the Yale Food Addiction Scale (YFAS) in 178 (133 F, 45M) persons seeking weight loss treatment. Participants had a mean age of 51.2±11.7years and a body mass index of 36.1±4.8kg/m(2). Fifteen percent of individuals met the YFAS proposed diagnostic criteria for FA. Those who met criteria for FA reported significantly greater depressive symptomatology. There were no differences in BMI, age, race, or gender between participants with and without FA. Among those not meeting criteria, 35% reported 3 or more symptoms in the absence of self-reported clinical distress or impairment. YFAS symptom count was also significantly correlated with depressive symptoms. These findings suggest that 15% of adults presenting for weight loss treatment meet YFAS criteria for FA. The clinical significance of this classification is unknown and needs to be validated in prospective studies.

An examination of food addiction in a racially diverse sample of obese patients with binge eating disorder in primary care settings

OBJECTIVE

The concept of food addiction in obesity and binge eating disorder (BED) continues to be a hotly debated topic yet the empirical evidence on the relationship between addictive-like eating and clinically relevant eating disorders is limited. The current study examined the association of food addiction as assessed by the Yale Food Addiction Scale (YFAS) with measures of disordered eating, dieting/weight history, and related psychopathology in a racially diverse sample of obese patients with binge eating disorder (BED).

METHOD

A consecutive series of 96 obese patients with BED who were seeking treatment for obesity and binge eating in primary care were given structured interviews to assess psychiatric disorders and eating disorder psychopathology and a battery of self-report measures including the YFAS to assess food addiction.

RESULTS

Classification of food addiction was met by 41.5% (n=39) of BED patients. Patients classified as meeting YFAS food addiction criteria had significantly higher levels of negative affect, emotion dysregulation, and eating disorder psychopathology, and lower self-esteem. Higher scores on the YFAS were related to an earlier age of first being overweight and dieting onset. YFAS scores were also significant predictors of binge eating frequency above and beyond other measures.

DISCUSSION

Compared to patients not classified as having food addiction, the subset of 41.5% of BED patients who met the YFAS food addiction cut-off appears to have a more severe presentation of BED and more associated pathology.

Food-related impulsivity in obesity and binge eating disorder--a systematic review

Impulsivity towards food has been recognized as a potential factor leading to increased food intake in obesity. Patients suffering from binge eating disorder (BED) form a specific subgroup of obese people that might be characterized by increased impulsivity. These assumptions, although, have yet to be verified. Therefore, this review evaluates evidence for food-related impulsivity in obese people with and without BED and examines possible differences between both populations. More precisely, evidence for the two components of impulsivity is analyzed separately: evidence for reward sensitivity, specifically, the urge for appetitive stimuli and evidence for rash-spontaneous behaviour such as acting disinhibited with no regard for the consequences. Our search resulted in 51 articles demonstrating generally increased food-related impulsivity. We found particular emphasis on increased reward sensitivity in obese people, which appeared to be more pronounced in people with BED. There was little and conflicting evidence, however, concerning increased rash-spontaneous behaviour in obese people without BED, but consistent evidence of an increase in obese people with BED. All in all, the evidence supports the view that BED represents a specific phenotype of obesity with increased food-related impulsivity. Taking these specific deficits into account can enhance the effectiveness of weight reduction programmes and psychotherapy.

Atypical depressive symptoms and obesity in a national sample of older adults with major depressive disorder

BACKGROUND

The objectives of this study are to present findings on the rate of obesity associated with classic, atypical, and undifferentiated depression by comparing with those without depression in a nationally representative sample of United States older adults.

METHODS

The authors used data from the 2001 to 2002 National Epidemiologic Survey of Alcohol and Related Conditions (NESARC), which included 10,557 adults 60 years of age and older. Chi-square tests were used to compare classic, atypical, and undifferentiated as well as nondepressed control in sociodemographic characteristics. Then, logistic regressions adjusting for sociodemographic characteristics were used to evaluate associations of rate of current obesity (defined as Body Mass Index (BMI) > 30) across the three depressive groups (classic, atypical, and undifferentiated depression) and nondepressed control. Lifetime, current, and past depression were examined.

RESULTS

Significant differences were found between atypical and classic depression in sex, age, marital status, race, and personal income. After adjusting for sex, age, marital status, race, and personal income, the rate of obesity was significantly greater for respondents with atypical depression than respondents with classic, undifferentiated depression, or without depression. Same results were found in lifetime, current, and past depression.

CONCLUSION

Our findings suggest that the heterogeneity of depression should be considered when examining the effect of depression on obesity in old age. Prevention measures should be designed and delivered to older adults with atypical depression.

From passive overeating to "food addiction": a spectrum of compulsion and severity

A psychobiological dimension of eating behaviour is proposed, which is anchored at the low end by energy intake that is relatively well matched to energy output and is reflected by a stable body mass index (BMI) in the healthy range. Further along the continuum are increasing degrees of overeating (and BMI) characterized by more severe and more compulsive ingestive behaviours. In light of the many similarities between chronic binge eating and drug abuse, several authorities have adopted the perspective that an apparent dependence on highly palatable food-accompanied by emotional and social distress-can be best conceptualized as an addiction disorder. Therefore, this review also considers the overlapping symptoms and characteristics of binge eating disorder (BED) and models of food addiction, both in preclinical animal studies and in human research. It also presents this work in the context of the modern and "toxic" food environment and therein the ubiquitous triggers for over-consumption. We complete the review by providing evidence that what we have come to call "food addiction" may simply be a more acute and pathologically dense form of BED.

Ethical Considerations in Deep Brain Stimulation for the Treatment of Addiction and Overeating Associated With Obesity

The success of deep brain stimulation (DBS) for movement disorders and the improved understanding of the neurobiologic and neuroanatomic bases of psychiatric diseases have led to proposals to expand current DBS applications. Recent preclinical and clinical work with Alzheimer's disease and obsessive-compulsive disorder, for example, supports the safety of stimulating regions in the hypothalamus and nucleus accumbens in humans. These regions are known to be involved in addiction and overeating associated with obesity. However, the use of DBS targeting these areas as a treatment modality raises common ethical considerations, which include informed consent, coercion, enhancement, threat to personhood, and manipulation of the reward center. Pilot studies for both of these conditions are currently investigational. If these studies show promise, then there is a need to address the ethical concerns related to the initiation of clinical trials including the reliability of preclinical evidence, patient selection, study design, compensation for participation and injury, cost-effectiveness, and the need for long-term follow-up. Multidisciplinary teams are necessary for the ethical execution of such studies. In addition to establishing safety and efficacy, the consideration of these ethical issues is vital to the adoption of DBS as a treatment for these conditions. We offer suggestions about the pursuit of future clinical trials of DBS for the treatment of addiction and overeating associated with obesity and provide a framework for addressing ethical concerns related to treatment.

Neural and behavioral effects of a novel mu opioid receptor antagonist in binge-eating obese people

BACKGROUND

Binge eating is associated with obesity and has been conceptualized as "food addiction." However, this view has received only inconsistent support in humans, and limited evidence relates key neurocircuitry to the disorder. Moreover, relatively few studies have used pharmacologic functional magnetic resonance imaging to probe the underlying basis of altered eating behaviors.

METHODS

In a double-blind, placebo-controlled, parallel group study, we explored the effects of a potent mu-opioid receptor antagonist, GSK1521498, in obese individuals with moderate binge eating. Subjects were tested during a baseline placebo run-in period and retested after 28-days of drug (n = 21) or placebo (n = 21) treatment. Using functional magnetic resonance imaging and behavioral measures, we determined the drug's effects on brain responses to food images and, separately, on motivation to expend energy to view comparable images.

RESULTS

Compared with placebo, GSK1521498 was associated with a significant reduction in pallidum/putamen responses to pictures of high-calorie food and a reduction in motivation to view images of high-calorie food. Intriguingly, although motivational responding was reduced, subjective liking for the same images actually increased following drug treatment.

CONCLUSIONS

Stimulus-specific putamen/pallidal responses in obese people with binge eating are sensitive to altered mu-opioid function. This neuromodulation was accompanied by reductions in motivational responding, as measured by grip force, although subjective liking responses to the same stimuli actually increased. As well as providing evidence for a link between the opioid system and food-related behavior in binge-eating obese individuals, these results support a dissociation across measures of motivation and liking associated with food-related stimuli in these individuals.

Monetary reward processing in obese individuals with and without binge eating disorder

BACKGROUND

An important step in obesity research involves identifying neurobiological underpinnings of nonfood reward processing unique to specific subgroups of obese individuals.

METHODS

Nineteen obese individuals seeking treatment for binge eating disorder (BED) were compared with 19 non-BED obese individuals (OB) and 19 lean control subjects (LC) while performing a monetary reward/loss task that parses anticipatory and outcome components during functional magnetic resonance imaging. Differences in regional activation were investigated in BED, OB, and LC groups during reward/loss prospect, anticipation, and notification.

RESULTS

Relative to the LC group, the OB group demonstrated increased ventral striatal and ventromedial prefrontal cortex activity during anticipatory phases. In contrast, the BED group relative to the OB group demonstrated diminished bilateral ventral striatal activity during anticipatory reward/loss processing. No differences were observed between the BED and LC groups in the ventral striatum.

CONCLUSIONS

Heterogeneity exists among obese individuals with respect to the neural correlates of reward/loss processing. Neural differences in separable groups with obesity suggest that multiple, varying interventions might be important in optimizing prevention and treatment strategies for obesity.

Increased prefrontal and parahippocampal activation with reduced dorsolateral prefrontal and insular cortex activation to food images in obesity: a meta-analysis of fMRI studies

Background and Objectives

Obesity is emerging as the most significant health concern of the twenty-first century. A wealth of neuroimaging data suggest that weight gain might be related to aberrant brain function, particularly in prefrontal cortical regions modulating mesolimbic addictive responses to food. Nevertheless, food addiction is currently a model hotly debated. Here, we conduct a meta-analysis of neuroimaging data, examining the most common functional differences between normal-weight and obese participants in response to food stimuli.

Data Source

We conducted a search using several journal databases and adhered to the ‘Preferred Reporting Items for Systematic Reviews and Meta-analyses’ (PRISMA) method. To this aim, 10 studies were found with a total of 126 obese participants, 129 healthy controls, equaling 184 foci (146 increased, 38 decreased activation) using the Activation Likelihood Estimation (ALE) technique. Out of the 10 studies, 7 investigated neural responses to food versus non-food images.

Results

In response to food images, obese in comparison to healthy weight subjects had increased activation in the left dorsomedial prefrontal cortex, right parahippocampal gyrus, right precentral gyrus and right anterior cingulate cortex, and reduced activation in the left dorsolateral prefrontal cortex and left insular cortex.

Conclusions

Prefrontal cortex areas linked to cognitive evaluation processes, such as evaluation of rewarding stimuli, as well as explicit memory regions, appear most consistently activated in response to images of food in those who are obese. Conversely, a reduced activation in brain regions associated with cognitive control and interoceptive awareness of sensations in the body might indicate a weakened control system, combined with hypo-sensitivity to satiety and discomfort signals after eating in those who are prone to overeat.

If sugar is addictive…what does it mean for the law?

Newly emerging links between sugar and addiction raise challenging issues for public health policy. What was once a naturally occurring food ingredient is now a highly concentrated food additive. If foods containing artificially high levels of sugar are capable of triggering addictive behaviors, how should policymakers respond? What regulatory steps would be suitable and practical? This paper explores the concept and definition of addiction and presents evidence of the addictive potential of sugar. It also explores the legal implications if sufficient evidence demonstrates that sugar is indeed addictive.

Fructose: it's "alcohol without the buzz"

What do the Atkins Diet and the traditional Japanese diet have in common? The Atkins Diet is low in carbohydrate and usually high in fat; the Japanese diet is high in carbohydrate and usually low in fat. Yet both work to promote weight loss. One commonality of both diets is that they both eliminate the monosaccharide fructose. Sucrose (table sugar) and its synthetic sister high fructose corn syrup consist of 2 molecules, glucose and fructose. Glucose is the molecule that when polymerized forms starch, which has a high glycemic index, generates an insulin response, and is not particularly sweet. Fructose is found in fruit, does not generate an insulin response, and is very sweet. Fructose consumption has increased worldwide, paralleling the obesity and chronic metabolic disease pandemic. Sugar (i.e., fructose-containing mixtures) has been vilified by nutritionists for ages as a source of "empty calories," no different from any other empty calorie. However, fructose is unlike glucose. In the hypercaloric glycogen-replete state, intermediary metabolites from fructose metabolism overwhelm hepatic mitochondrial capacity, which promotes de novo lipogenesis and leads to hepatic insulin resistance, which drives chronic metabolic disease. Fructose also promotes reactive oxygen species formation, which leads to cellular dysfunction and aging, and promotes changes in the brain's reward system, which drives excessive consumption. Thus, fructose can exert detrimental health effects beyond its calories and in ways that mimic those of ethanol, its metabolic cousin. Indeed, the only distinction is that because fructose is not metabolized in the central nervous system, it does not exert the acute neuronal depression experienced by those imbibing ethanol. These metabolic and hedonic analogies argue that fructose should be thought of as "alcohol without the buzz."

Neurobiology of addiction versus drug use driven by lack of choice

Research on the neurobiology of addiction often involves nonhuman animals that are given ready access to drugs for self-administration but without other choices. Here we argue using cocaine as an example that this standard setting may no longer be sufficient and can even lead to the formulation of unrealistic views about the neurobiology of addiction. Addiction as a psychiatric disorder is defined as resulting from brain dysfunctions that affect normal choice-making, not as an expectable response to lack of alternative choices. We encourage neurobiologists involved in addiction research to increase animals' choice during drug access, preferably by supplying alternative rewarding pursuits. Only animals that continue to take and prefer drugs despite and at the expense of other available choices may be considered as having developed an addiction-like behavior in comparison to those that remain able to stop drug use for other pursuits, even after extended drug use. The systematic comparison of these two individual behaviors should reveal new insights about the neurobiology of drug choice and addiction. More generally, this research should also shed a unique light on how the brain 'chooses' among qualitatively different kinds of pursuits.