Implications from addiction research towards the understanding and treatment of obesity

Dysregulated resting state functional connectivity and obesity: A systematic review

Obesity has been variously linked to differences in brain functional connectivity in regions associated with reward, emotional regulation and cognition, potentially revealing neural mechanisms contributing to its development and maintenance. This systematic review summarizes and critically appraises the existing literature on differences in resting state functional connectivity (Rs-FC) between overweight and individuals with obesity in relation healthy-BMI controls. Twenty-nine studies were identified and the results consistently support the hypothesis that obesity is associated with differences in Rs-FC. Specifically, obesity/overweight was consistently associated with (i) DMN hypoconnectivity and salience network hyperconnectivity; (ii) increased Rs-FC between the hypothalamus and reward, limbic and salience networks, and decreased Rs-FC between the hypothalamus and cognitive regions; (iii) increased power within regions associated with inhibition/emotional reasoning; (iv) decreased nodal efficiency, degree centrality, and global efficiency. Collectively, the results suggest obesity is associated with disrupted connectivity of brain networks responsible for cognition, reward, self-referential processing and emotional regulation.

Auswirkungen des Lockdowns im Frühjahr 2020 während der COVID-19-Pandemie auf das Ess- und Sportverhalten – Ergebnisse einer Onlinebefragung

Einleitung Die Ausgangseinschränkungen und Kontaktverbote während der COVID-19-Pandemie haben mit dem Wegfall vieler beruflicher und privater Verpflichtungen und Strukturen massive Auswirkungen auf den Alltag der Allgemeinbevölkerung. Gleichzeitig verstärken sich für viele Menschen die Sorgen vor allem bezüglich ihrer finanziellen und beruflichen Zukunft. Eine vermehrte Nahrungsaufnahme stellt in dieser Situation eine mögliche Bewältigungsstrategie im Umgang mit den als unangenehm erlebten Gefühlen dar. Gleichzeitig fallen wegen der Ausgangs- und Kontaktbeschränkungen viele Möglichkeiten zur sportlichen Betätigung weg. Dies birgt die Gefahr einer Zunahme der kardiovaskulären Risikofaktoren in der Allgemeinbevölkerung und insbesondere für die Entstehung von Adipositas sowie Diabetes mellitus Typ 2. In dieser Studie untersuchten wir daher die Veränderungen des Ess- und Sportverhaltens in der Allgemeinbevölkerung in Deutschland während des Lockdowns im Frühjahr 2020.

Material und Methodik An der Onlinebefragung zu Veränderungen des Ess- und Sportverhaltens während des Lockdowns im Frühjahr 2020 konnten Frauen und Männer zwischen 18 und 80 Jahren aus der Allgemeinbevölkerung teilnehmen. Die Umfrage war online verfügbar zwischen dem 8. April und dem 11. Mai 2020.

Ergebnisse Von 3259 Teilnehmern gaben 40,3 % an, während des Lockdowns mehr als vor dessen Beginn gegessen zu haben, 38,3 % berichteten, während des Lockdowns weniger Sport gemacht zu haben als in der Zeit davor. Bei einer kombinierten Betrachtung der Verhaltensänderungen zeigten 58,5 % der Teilnehmer mindestens eine Verhaltensänderung, die dauerhaft potenziell negative gesundheitliche Folgen für sie haben könnte und die Entwicklung eines Diabetes mellitus Typ 2 fördert. Mit 18,5 % aller Studienteilnehmer gab die größte Gruppe an, weniger Sport gemacht und gleichzeitig mehr gegessen zu haben während des Lockdowns.

Schlussfolgerungen Diese Ergebnisse weisen darauf hin, dass es sowohl in der ambulanten als auch in der stationären Patientenversorgung in den nächsten Monaten wichtig sein wird, die Patienten auf die Gesundheitsrisiken, die sich durch eine Reduktion von sportlicher Aktivität und eine vermehrte Nahrungsaufnahme ergeben, hinzuweisen und ihr Ess- und Sportverhalten sowie die Veränderung des Körpergewichts zu beobachten, um eine Zunahme des Risikos für Diabetes mellitus Typ 2 in der Allgemeinbevölkerung zu verhindern.

Pupil dilation as an implicit measure of appetitive Pavlovian learning

Appetitive Pavlovian conditioning is a learning mechanism of fundamental biological and pathophysiological significance. Nonetheless, its exploration in humans remains sparse, which is partly attributed to the lack of an established psychophysiological parameter that aptly represents conditioned responding. This study evaluated pupil diameter and other ocular response measures (gaze dwelling time, blink duration and count) as indices of conditioning. Additionally, a learning model was used to infer participants' learning progress on the basis of their pupil dilation. Twenty-nine healthy volunteers completed an appetitive differential delay conditioning paradigm with a primary reward, while the ocular response measures along with other psychophysiological (heart rate, electrodermal activity, postauricular and eyeblink reflex) and behavioral (ratings, contingency awareness) parameters were obtained to examine the relation among different measures. A significantly stronger increase in pupil diameter, longer gaze duration and shorter eyeblink duration was observed in response to the reward-predicting cue compared to the control cue. The Pearce-Hall attention model best predicted the trial-by-trial pupil diameter. This conditioned response was corroborated by a pronounced heart rate deceleration to the reward-predicting cue, while no conditioning effect was observed in the electrodermal activity or startle responses. There was no discernible correlation between the psychophysiological response measures. These results highlight the potential value of ocular response measures as sensitive indices for representing appetitive conditioning.

A Critical Examination of the Practical Implications Derived from the Food Addiction Concept

PURPOSE OF REVIEW

Adopting an addiction perspective on eating disorders and obesity may have practical implications for diagnostic classification, prevention, and treatment of these disorders. The present article critically examines these implications derived from the food addiction concept.

RECENT FINDINGS

Introducing food addiction as a new disorder in diagnostic classification system seems redundant as most individuals with an addiction-like eating behavior are already covered by established eating disorder diagnoses. Food addiction may be a useful metaphor in the treatment of binge eating, but would be inappropriate for the majority of obese individuals. Implying an addiction to certain foods is not necessary when applying certain approaches inspired by the addiction field for prevention and treatment of obesity. The usefulness of abstinence models in the treatment of eating disorders and obesity needs to be rigorously tested in future studies. Some practical implications derived from the food addiction concept provide promising avenues for future research (e.g., using an addiction framework in the treatment of binge eating or applying abstinence models). For others, however, the necessity of implying an addiction to some foods needs to be scrutinized.

Impulsiveness in Reactive Dieters: Evidence From Delay Discounting in Orthodontic Patients

Introduction: Researchers have made efforts to distinguish the behavioral differences and underlying mechanisms that explain the various possible outcomes of dieting (success, failure and relapse). Although extensive research has demonstrated that eating behavior and individual impulsiveness are closely related to subjective appetite and decision making, very few studies have investigated how subjective and appetite impulsiveness is affected by reactive dieting. Methods: In the present study, we utilized the power of food scale (PFS) and the intertemporal choice task and to examine subjective appetite and impulsivity of decision making in orthodontic patients. As a result of their orthodontic devices and the subsequent pain and discomfort caused by eating, these patients become reactive dieters. In order to explore the dynamic influence of orthodontic treatment on appetite and impulsiveness, we collected data for both patients and control participants across three testing sections. We also computed a regression model for further exploration in explaining how potential factors contributed to different choices. Results: We found that the orthodontic group scored significantly lower in PFS than the control group, which indicated a suppression in appetite. Besides, reward and waiting time were significant factors in computational perspective. Moreover, although patients showed a bias in choosing smaller, immediate reward options, they exhibited a decrease in the delay discounting rate as treatment progressed. These findings confirm that subjective appetite and impulsiveness were inhibited due to reactive dieting.

Mood and restrained eating moderate food-associated response inhibition in obese individuals with binge eating disorder

Recent research suggests that obese individuals with binge eating disorder (BED) show deficits in response inhibition, but findings are not consistent, especially when food-associated stimuli are presented. The aim of the present study was to assess the role of moderating factors by taking into account restrained eating and mood. Seventeen obese women with BED, 20 obese women without BED and 20 normal-weight controls (NW) were recruited. A go/no-go task with food-associated and control stimuli and questionnaires were administered. Obese BED showed less impairment of response inhibition to food-associated than to control stimuli, while this pattern was reversed in NW; no differences were observed for obese participants. Interestingly, group differences were moderated by the interaction of restrained eating and mood, and obese BED made the most commission errors to food-associated stimuli when they were restrained eaters and in a very positive mood at the time of testing. Our results might explain why some studies did not observe deficits in response inhibition to food-associated cues in BED.

A review of the neurobiology of obesity and the available pharmacotherapies

Obesity is becoming an increasing problem worldwide. In addition to causing many physical health consequences, there is increasing evidence demonstrating that obesity is toxic to the brain and, as such, can be considered a disease of the central nervous system. Peripheral level regulators of appetite, such as leptin, insulin, ghrelin, and cholecystokinin, feed into the appetite center of the brain, which is controlled by the hypothalamus, to maintain homeostasis and energy balance. However, food consumption is not solely mediated by energy balance, but is also regulated by the mesolimbic reward system, where motivation, reward, and reinforcement factors influence obesity. The purpose of this review is to highlight the neurobiology of eating behavior and obesity and to describe various neurobiological treatment mechanisms to treat obesity.

Behavioral sensitization of the reinforcing value of food: What food and drugs have in common

Sensitization is a basic property of the nervous system whereby repeated exposure to a stimulus results in an increase in responding to that stimulus. This increase in responding contributes to difficulty with treatment of drug abuse, as stimuli associated with substance use become signals or triggers for drug craving and relapse. Our work over the past decade has applied the theoretical framework of incentive sensitization to overeating. We have shown, in several studies, that lean adults do not commonly demonstrate behavioral sensitization after repeated exposure to snack food, but a subset of obese adults reliably does. This review will discuss this change in behavioral response to repeated consumption of snack food in obese individuals and apply the theoretical framework of incentive sensitization to drugs of abuse to high fat/high sugar snack foods. We will also show data that suggest that behavioral sensitization to repeated administration of snack food is predictive of weight gain, which may enhance its utility as a diagnostic tool for identifying at-risk individuals for obesity. Finally, we will discuss the future directions of this line of research, including studying the phenomenon in children and adolescents and determining if similar principles can be used to increase motivation to eat healthier food. A combination of reductions in unhealthy food intake and increases and healthy food intake is necessary to reduce obesity rates and improve health.

Advances in nicotine research in Addiction Biology

The aim of Addiction Biology is to advance our understanding of the action of drugs of abuse and addictive processes via the publication of high-impact clinical and pre-clinical findings resulting from behavioral, molecular, genetic, biochemical, neurobiological and pharmacological research. As of 2013, Addiction Biology is ranked number 1 in the category of Substance Abuse journals (SCI). Occasionally, Addiction Biology likes to highlight via review important findings focused on a particular topic and recently published in the journal. The current review summarizes a number of key publications from Addiction Biology that have contributed to the current knowledge of nicotine research, comprising a wide spectrum of approaches, both clinical and pre-clinical, at the cellular, molecular, systems and behavioral levels. A number of findings from human studies have identified, using imaging techniques, alterations in common brain circuits, as well as morphological and network activity changes, associated with tobacco use. Furthermore, both clinical and pre-clinical studies have characterized a number of mechanistic targets critical to understanding the effects of nicotine and tobacco addiction. Together, these findings will undoubtedly drive future studies examining the dramatic impact of tobacco use and the development of treatments to counter nicotine dependence.

Evidence for a compulsive-like behavior in rats exposed to alternate access to highly preferred palatable food

Converging evidence suggests that recurrent excessive calorie restriction causes binge eating by promoting behavioral disinhibition and overeating. This interpretation suggests that cognitive adaptations may surpass physiological regulations of metabolic needs after recurrent cycles of dieting and binging. Intermittent access to palatable food has long been studied in rats, but the consequences of such diet cycling procedures on the cognitive control of food seeking remain unclear. Female Wistar rats were divided in two groups matched for food intake and body weight. One group received standard chow pellets 7 days/week, whereas the second group was given chow pellets for 5 days and palatable food for 2 days over seven consecutive weeks. Rats were also trained for operant conditioning. Intermittent access to palatable food elicited binging behavior and reduced intake of normal food. Rats with intermittent access to palatable food failed to exhibit anxiety-like behaviors in the elevated plus maze, but displayed reduced locomotor activity in the open field and developed a blunted corticosterone response following an acute stress across the diet procedure. Trained under a progressive ratio schedule, both groups exhibited the same motivation for sweetened food pellets. However, in contrast to controls, rats with a history of dieting and binging exhibited a persistent compulsive-like behavior when access to preferred pellets was paired with mild electrical foot shock punishments. These results highlight the intricate development of anxiety-like disorders and cognitive deficits leading to a loss of control over preferred food intake after repetitive cycles of intermittent access to palatable food.

Addiction to sugar and its link to health morbidity: a primer for newer primary care and public health initiatives in Malaysia

OBJECTIVES

The average consumption of sugar in the Malaysian population has reached an alarming rate, exceeding the benchmark recommended by experts. This article argues the need of a paradigm shift in the management of sugar consumption in the country through evidence derived from addiction research.

METHODS

"Food addiction" could lead to high levels of sugar consumption. This probable link could accelerate the development of diabetes and obesity in the community. A total of 94 reports and studies that describe the importance of addiction theory-based interventions were found through a search on PubMed, Google Scholar, and Academic Search Complete.

RESULTS

Research in the field of addiction medicine has revealed the addictive potential of high levels of sugar intake. Preexisting health promotion strategies could benefit from the integration of the concept of sugar addiction. A targeted intervention could yield more positive results in health outcomes within the country.

CONCLUSION

Current literature seems to support food environment changes, targeted health policies, and special consultation skills as cost-effective remedies to curb the rise of sugar-related health morbidities.

Joint and independent effects of alcohol drinking and tobacco smoking on oral cancer: a large case-control study

Alcohol drinking and tobacco smoking are assumed to have significant independent and joint effects on oral cancer (OC) development. This assumption is based on consistent reports from observational studies, which, however, overestimated the independent effects of smoking and drinking, because they did not account for the interaction effect in multivariable analyses. This case-control study sought to investigate the independent and the joint effects of smoking and drinking on OC in a homogeneous sample of adults. Case patients (N = 1,144) were affected by invasive oral/oropharyngeal squamous cell carcinoma confirmed histologically, diagnosed between 1998 and 2008 in four hospitals of São Paulo (Brazil). Control patients (N = 1,661) were not affected by drinking-, smoking-associated diseases, cancers, upper aero-digestive tract diseases. Cumulative tobacco and alcohol consumptions were assessed anamnestically. Patients were categorized into never/ever users and never/level-1/level-2 users, according to the median consumption level in controls. The effects of smoking and drinking on OC adjusted for age, gender, schooling level were assessed using logistic regression analysis; Model-1 did not account for the smoking-drinking interaction; Model-2 accounted for this interaction and included the resultant interaction terms. The models were compared using the likelihood ratio test. According to Model-1, the adjusted odds ratios (ORs) for smoking, drinking, smoking-drinking were 3.50 (95% confidence interval –95CI, 2.76–4.44), 3.60 (95CI, 2.86–4.53), 12.60 (95CI, 7.89–20.13), respectively. According to Model-2 these figures were 1.41 (95CI, 1.02–1.96), 0.78 (95CI, 0.48–1.27), 8.16 (95CI, 2.09–31.78). Analogous results were obtained using three levels of exposure to smoking and drinking. Model-2 showed statistically significant better goodness-of-fit statistics than Model-1. Drinking was not independently associated with OC, while the independent effect of smoking was lower than expected, suggesting that observational studies should be revised adequately accounting for the smoking-drinking interaction. OC control policies should focus on addictive behaviours rather than on single lifestyle risk factors.

Obesity and mental illness: implications for cognitive functioning

A priority research and clinical agenda is to identify determinants of cognitive impairment in individuals with neuropsychiatric disorders (NPD). The bidirectional association between NPD and cognitive performance has been reported to be mediated and/or moderated by obesity in a subset of individuals. Obesity can be conceptualized as a neurotoxic phenotype among individuals with NPD as evidenced by alterations in the structure and function of neural circuits and disseminated networks, diminished cognitive performance, and adverse effects on illness trajectory. The neurotoxic effect of obesity provides a rationale for screening, treating, and preventing obesity in neuropsychiatric populations. Research endeavors that aim to refine mediators and moderators of this association as well as novel strategies to reverse the injurious process of obesity on cognition are warranted.

U, R.L.W. C. 2-Hydroxyestradiol enhances binge onset in female rats and reduces prefrontal cortical dopamine in male rats

Women are more likely to suffer from a bingeing-related eating disorder, which is surprising, since estradiol reduces meal size and is associated with reduced binge frequency. This apparent contradiction may involve the estradiol metabolite, 2-hydroxyestradiol. We previously reported that female rats had faster escalations in shortening intake during the development of bingeing than did males, but acute administration of 2-hydroxyestradiol increased the intake of vegetable shortening to a greater extent in male rats once bingeing was established. Here, we report two separate studies that follow up these previous findings. In the first, we hypothesized that chronic exposure to 2-hydroxyestradiol would promote escalation of bingeing during binge development in ovariectomized female rats. In the second, we hypothesized that acute exposure to 2-hydroxyestradiol would enhance dopamine signaling in the prefrontal cortex after bingeing was established in male rats. In study 1, non-food-deprived female rats were separated into 3 groups: ovariectomized (OVX) with chronic 2-hydroxyestradiol supplementation (E), OVX with vehicle supplementation (O), and intact with vehicle (I). Each group was given access to an optional source of dietary fat (shortening) on Mon, Wed, and Fri for 4 weeks. 2-hydroxyestradiol supplementation prevented OVX-induced weight gain and enhanced escalation of shortening intake over the four-week period (ps<0.05). Additionally, in week 4, rats in the E group ate significantly more shortening than I controls, less chow than either the O or I group, and had a higher shortening to chow ratio than O or I (ps<0.05). Study 2 indicated that acute injection of 2-hydroxyestradiol abolished shortening-evoked dopamine efflux in the prefrontal cortex of bingeing male rats (p<0.05). Together, these studies indicate that 2-hydroxyestradiol can exacerbate bingeing as it develops and can suppress dopamine signaling in the prefrontal cortex once bingeing is established.

Attentional Processing of Food Cues in Overweight and Obese Individuals

The incentive sensitization model of obesity hypothesizes that obese individuals in the western world have acquired an enhanced attention bias to food cues, because of the overwhelming exposure to food. This article gives an overview of recent studies regarding attention to food and obesity. In general, an interesting approach-avoidance pattern in food-related attention has been found in overweight/obese individuals in a number of studies. However, it should be noted that study results are contradictory. This might be due to methodological issues, such as the choice of attention measurements, possibly tapping different underlying components of information processing. Although attention research is challenging, researchers are encouraged to further explore important issues, such as the exact circumstances in which obese persons demonstrate enhanced attention to food, the directional relationship between food-related attention bias, overeating and weight gain, and the underlying involvement of the reward system. Knowledge on these issues could help improve treatment programs.