Psychobiological traits in the risk profile for overeating and weight gain. Int J Obes (Lond). 2009;33 Suppl 2:S49-S53. [PMID: 19528980 DOI: 10.1038/ijo.2009.72]

Genetic evidence for the causal relations between metabolic syndrome and psychiatric disorders: a Mendelian randomization study

Emerging evidence reveals associations between metabolic syndrome (MetS) and psychiatric disorders (PDs), although causality remains uncertain. Consequently, we conducted Mendelian randomization (MR) to systematically evaluate the causality between MetS and PDs. Linkage disequilibrium score regression estimated the heritability of PDs and their genetic correlations with MetS. In primary analyses, the main model employed inverse variance weighting method, with sensitivity analyses using various MR models to ensure robustness. Replication MR analyses, involving cohorts distinct from those in the primary analyses, were performed to validate the generalizability of the findings. Multivariable MR analyses were carried out to account for genetically predicted body mass index (BMI). As a result, genetic correlations of MetS with attention-deficit/hyperactivity disorder(ADHD), anorexia nervosa(ANO), major depressive disorder(MDD), and schizophrenia were identified. Causal effects of MetS on ADHD (OR: 1.59 [95% CI:1.45-1.74]), ANO (OR: 1.42 [95% CI:1.25-1.61]), MDD(OR: 1.23 [95% CI: 1.13-1.33]), and the effects of ADHD (OR: 1.03 [95% CI: 1.02-1.04]) and ANO (OR: 1.01 [95% CI: 1.01-1.02]) on MetS were observed in primary analyses. Results from sensitivity analyses and replication analyses were generally consistent with the primary analyses, confirming the robustness and generalizability of the findings. Associations between MetS and ADHD, as well as ANO persisted after adjusting for BMI, whereas the statistical significance of the association between MetS and MDD was no longer observable. These results contribute to a deeper understanding of the mechanisms underlying PDs, suggesting potential modifiable targets for public prevention and clinical intervention in specific PDs related to metabolic pathways.

Intuitive eating and its influence on self-reported weight and eating behaviors

Intuitive eating (IE) is an adaptive eating behavior that involves paying attention to the body's physiological signals, including eating when hungry and stopping when feeling full. A growing body of literature has examined the effect of IE on the development of maladaptive eating behaviors and body weight, even though IE is not centered around the latter. However, longitudinal observation studies among the general population are still rare. Therefore, this study aimed to longitudinally examine the links between IE and changes in body weight, maladaptive eating behaviors (reward, external, restrained eating), and overeating frequency over time. For this purpose, we used data from the first (2017) and the fourth waves (2020) of the Swiss Food Panel 2.0 survey, which included 1821 randomly selected Swiss participants. The same participants completed a self-administered questionnaire annually, measuring their self-reported eating behaviors and weight status. IE was measured with the Intuitive Eating Scale-2. Results showed that women with high IE scores were more likely to maintain their body weights (within ±2 kg) and less likely to gain weight (>2 kg) than women with low IE scores. No such effects were found for men. Furthermore, IE was linked to a reduction in maladaptive eating behaviors and overeating frequency over time in both genders. Results suggest that IE may counteract maladaptive eating behaviors, which can promote weight stability over time. Therefore, the encouragement of IE patterns seems to be a promising strategy to address problematic eating behaviors and the challenges associated with controlling food intake and prevention of overeating.

No effect of prefrontal transcranial direct current stimulation (tDCS) on food craving, food reward and subjective appetite in females displaying mild-to-moderate binge-type behaviour

Previous work suggests there may be an effect of transcranial direct current stimulation (tDCS) on appetite control in people at risk of overconsumption, however findings are inconsistent. This study aimed to further understand the potential eating behaviour trait-dependent effect of tDCS, specifically in those with binge-type behaviour. Seventeen females (23 ± 7 years, 25.4 ± 3.8 kg m-2) with mild-to-moderate binge eating behaviour completed two sessions of double-blind, randomised and counterbalanced anodal and sham tDCS applied over the right dorsolateral prefrontal cortex at 2.0 mA for 20 min. Subjective appetite visual analogue scales (VAS), the Food Craving Questionnaire-State (FCQ-S), and Leeds Food Preference Questionnaire (LFPQ) were completed pre- and post-tDCS. Participants then consumed a fixed-energy meal, followed by the VAS, FCQ-S and LFPQ. No difference between pre- and post-tDCS scores were found across fullness (p = 0.275, BF10 = 0.040), prospective consumption (p = 0.127, BF10 = 0.063), desire to eat (p = 0.247, BF10 = 0.054) or FCQ-S measures (p = 0.918, BF10 = 0.040) when comparing active and sham protocols. Only explicit liking and wanting for high-fat sweet foods were significantly different between conditions, with increased scores following active tDCS. When controlling for baseline hunger, the significant differences were removed (p = 0.138 to 0.161, BF10 = 0.810 to 1.074). The present data does not support the eating behaviour trait dependency of tDCS in a specific cohort of female participants with mild-to-moderate binge eating scores, and results align with those from individuals with healthy trait scores. This suggests participants with sub-clinical binge eating behaviour do not respond to tDCS. Future work should further explore effects in clinical and sub-clinical populations displaying susceptibility to overconsumption and weight gain.

Evaluation of Eating Habits and Nutrient Intake in Adolescents with and without Suspected Eating Disorders in Iran

Objective: Increasing the incidence of eating disorder (ED) attitude during adolescence may lead to inadequate nutrient intake and consequently to growth disorders. This study aimed to compare eating habits and nutrient intakes of adolescents with high risk and low risk of developing eating disorders in high schools in Tehran, Iran. Methods: In the current cross-sectional study, the Eating Attitude Test (EAT-26) was applied to 299 students (185 females and 114 males) aged 15-18 years for the determination of ED attitudes. Food habits and nutrient intake were assessed by a self-administered questionnaire and a validated Food Frequency Questionnaire (FFQ), respectively. Nutrient adequacy ratio (NAR) and mean adequacy ratio (MAR) were calculated using nutrient’s Dietary Reference Intake (DRI) for age and sex. Results: Of all students, 17.7% were at risk of developing ED. The results showed that girls, unlike boys, consumed more energy than they needed, but this difference between the ED group in both sexes was not significant. The distribution of sweetened drinks, candy, chocolate, and fast food frequency was significantly different between the two groups of girls (P

Core Neuropsychological Measures for Obesity and Diabetes Trials: Initial Report

Obesity and diabetes are known to be related to cognitive abilities. The Core Neuropsychological Measures for Obesity and Diabetes Trials Project aimed to identify the key cognitive and perceptual domains in which performance can influence treatment outcomes, including predicting, mediating, and moderating treatment outcome and to generate neuropsychological batteries comprised of well-validated, easy-to-administer tests that best measure these key domains. The ultimate goal is to facilitate inclusion of neuropsychological measures in clinical studies and trials so that we can gather more information on potential mediators of obesity and diabetes treatment outcomes. We will present the rationale for the project and three options for the neuropsychological batteries to satisfy varying time and other administration constraints. Future directions are discussed. Preprint version of the document is available at https://osf.io/preprints/nutrixiv/7jygx/.

Impulsivity and midlife cardiometabolic risk: The role of maladaptive health behaviors

OBJECTIVE

The present study evaluated distinct facets of impulsivity related to cardiometabolic risk (CMR) to identify specific behavioral mechanisms driving these relationships.

METHOD

Community adults (N = 1,295) between 30 and 54 years old (53% female, 84% White) completed a battery of impulsivity measures, reported their engagement in health behaviors over the past week (i.e., cigarette smoking, alcohol use, physical activity, and dietary intake), and were assessed for CMR factors (i.e., blood pressure, insulin resistance, adiposity, and blood lipids). Structural equation modeling was used to estimate previously established hierarchical models of distinct facets of impulsivity and CMR. Indirect effects through the observed health behaviors were examined for each association between the latent impulsivity factors identified and the latent CMR factor.

RESULTS

Neuroticism/negative emotionality was the only latent impulsivity factor directly related to heightened CMR (β = 0.09, 95% confidence interval [CI] [0.01, 0.16], p = .020). Extraversion/positive emotionality indirectly related to lower CMR through greater physical activity (β = -0.04, 95% CI [-0.06, -0.02], p < .001), and measures of inhibition (β = 0.02, 95% CI [0.001, 0.04], p = .045) and delay discounting (β = 0.08, 95% CI [0.001, 0.15], p = .049) indirectly related to CMR through saturated fat intake.

CONCLUSIONS

These findings indicate that distinct facets of impulsivity differentially relate to CMR through varied behavioral pathways and identify physical activity and saturated fat intake as being particularly important health behaviors to target when tailoring treatment approaches to the unique behavioral characteristics of individuals high on certain facets of impulsivity. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

A dual-process psychobiological model of temperament predicts liking and wanting for food and trait disinhibition

A dual-process model of temperament, incorporating the Behavioural Inhibition System (BIS), Behavioural Activation System (BAS) and effortful control (EC), may help to predict hedonic responses to palatable food and trait disinhibition.

PURPOSE

This study aimed to determine if the BIS, BAS and EC predicted liking and wanting for high-fat, sweet foods in adults with overweight and obesity, and if collectively, these variables predicted the eating behaviour trait of Disinhibition.

METHODS

168 adults (104 females, mean BMI = 33.3 kg/m²) completed the Three Factor Eating Questionnaire, the Carver and White BIS/BAS scales, the Adult Temperament Questionnaire-Effortful Control Scale - Short Form and the Leeds Food Preference Questionnaire. The strength of the BIS, BAS and EC in predicting wanting and liking for high-fat sweet foods, and trait Disinhibition was assessed using hierarchical multiple regression.

RESULTS

Both the BIS and EC predicted liking, F (6, 161) = 5.05, p < .001, R² = 0.16, and EC inversely predicted wanting, F (6, 161) = 3.28, p = .005, R² = 0.11. The BIS, EC and liking predicted, F (8, 159) = 11.0, p < .001, R² = 0.36, and explained 36% of Disinhibition. The BAS did not predict wanting, liking or Disinhibition.

CONCLUSIONS

These results demonstrate that a sensitive BIS and a lower level of effortful control predicts food reward and Disinhibition in overweight and obese adults. Consequently, interventions that aim to increase effortful control and reduce BIS reactivity may be beneficial for reducing hedonically motivated, disinhibited eating behaviour.

Top-down guidance of attention to food cues is enhanced in individuals with overweight/obesity and predicts change in weight at one-year follow up

Background

Changing eating behaviour may be challenging for individuals with obesity and this may be related to attentional bias towards food. Previous paradigms used to assess attentional bias to food stimuli have not distinguished between bottom-up processes related to assessment of rewarding stimuli versus top-down processes related to effects of mind-set on attention. We investigated whether attentional bias for food cues varies between individuals with overweight/obesity and healthy weight individuals, due to differential top-down control of attention. We also determined whether top-down biases predict food consumption in the lab and weight change in our sample over one-year.

Methods

Forty-three participants with overweight/obesity and 49 healthy weight participants between the ages of 18 and 58 participated. Participants completed two attention tasks in a counterbalanced order: (i) a priming task assessing bottom-up control of attention and (ii) a working memory task assessing top-down control of attention. Eating behaviour was assessed by a taste test. At one-year follow-up participants returned to the laboratory to assess changes in their body mass index (BMI).

Results

The healthy weight and overweight/obese groups did not differ in demographics and baseline measures (appetite, food liking, taste test food intake). Participants with overweight/obesity showed greater top-down attentional bias towards food cues than did healthy weight participants but had no difference in bottom-up attentional bias. Top down attentional bias towards food cues predicted weight change over one-year but did not predict food intake in the taste test.

Conclusions

The present findings illustrate that the relationship between attentional bias for food, food intake, and body weight is complex. Top-down effects of mind-set on attention, rather than bottom-up control of attention to food may contribute to patterns of eating that result in development and/or maintenance of overweight/obesity. Interventions targeted at top down biases could be effective in facilitating prevention of weight gain.

Associations between Attention-Deficit Hyperactivity Disorder (ADHD) Treatment and Patient Nutritional Status and Height

Attention-deficit hyperactivity disorder (ADHD) has been found to co-occur frequently with obesity, although the reasons for this association are unknown. The aim of this study was to compare the nutritional profile of a Brazilian cohort of ADHD patients with that of the general population and to analyze the association between ADHD drug treatment (with methylphenidate), nutritional status, and height of these individuals. In the first phase of the study, we designed the nutritional and height profile of 93 ADHD patients (5.1 to 13.8 years old) and compared it to a control group. In the second phase, we analyzed the association of the use of methylphenidate with nutritional status and height. The results showed that the prevalence of overweight/obesity was statistically higher in the cohort of ADHD patients compared to controls (40.9% vs. 34.7%; P < 0.05). After treating ADHD patients with methylphenidate, a statistically significant decrease in the BMI z-score was observed (0.695 vs. 0.305; P < 0.01). On the other hand, no significant impact on height was detected after treatment (0.189 vs. 0.248; P = 0.298). In conclusion, the results suggest that the use of methylphenidate in patients who have ADHD and obesity is relevant not only for controlling ADHD symptoms but also for improving the nutritional status of these individuals. Moreover, the treatment did not affect the patients' height.

Adult ADHD and Comorbid Somatic Disease: A Systematic Literature Review

OBJECTIVE

To systematically review, synthesize, and appraise available evidence, connecting adult ADHD with somatic disease.

METHOD

Embase, Psychinfo, and Medline databases were searched for studies published from 1994 to 2015 addressing adult ADHD and somatic comorbidity. Somatic conditions were classified according to International Classification of Diseases (ICD-10) codes. Levels of evidence were graded as inconclusive, tentative, or well documented.

RESULTS

Most of the 126 studies included in the qualitative synthesis were small and of modest quality. Obesity, sleep disorders, and asthma were well-documented comorbidities in adult ADHD. Tentative evidence was found for an association between adult ADHD and migraine and celiac disease. In a large health registry study, cardiovascular disease was not associated with adult ADHD.

CONCLUSION

There are few large systematic studies using standardized diagnostic criteria evaluating adult ADHD and somatic comorbidities. Significant associations are found between adult ADHD and several somatic diseases, and these are important to consider when assessing and treating either adult ADHD or the somatic diseases.

Relation of binge eating disorder with impulsiveness in obese individuals

AIM

To investigate the levels of impulsiveness, and the relationship between the binge eating disorder (BED) and the levels of impulsiveness in obese individuals.

METHODS

Two hundred and forty-one obese patients who were included in the study and candidate for bariatric surgery (weight loss surgery) were clinically interviewed to identify the BED group, and patients were divided into two groups: Those with BED and those without BED. The comorbidity rate of groups was determined by using structured clinical interview for DSM-IV (SCID-I). A sociodemographic data form including the story of previous psychiatric treatment, structured clinical interview for DSM-IV (SCID-I), Beck Anxiety Inventory, Beck Depression Inventory (BDI) and Barratt Impulsiveness Scale-11 were applied to both of the groups.

RESULTS

In regard to 241 obese individuals included in the study, total score and score of attention subscale for BED (+) group were significantly high (P < 0.05). In addition, suicide attempt, story of psychiatric consultation, and score for BDI were again significantly high in the BED (+) group (P < 0.05).

CONCLUSION

In assessment of obese individuals, assessment of associated psychopathology such as impulsive characteristics and suicide attempt in addition to disrupted eating behaviors will allow to have a more extensive view.

Overlapping Neural Endophenotypes in Addiction and Obesity

Impulsivity refers to a tendency to act rapidly without full consideration of consequences. The trait is thought to result from the interaction between high arousal responses to potential rewards and poor self-control. Studies have suggested that impulsivity confers vulnerability to both addiction and obesity. However, results in this area are unclear, perhaps due to the high phenotypic complexity of addictions and obesity. Focusing on impulsivity, the aim of this review is to tackle the putative overlaps between addiction and obesity in four domains: (1) personality research, (2) neurocognitive tasks, (3) brain imaging, and (4) clinical evidence. We suggest that three impulsivity-related domains are particularly relevant for our understanding of similarities between addiction and obesity: lower self-control (high Disinhibition/low Conscientiousness), reward sensitivity (high Extraversion/Positive Emotionality), and negative affect (high Neuroticism/Negative Emotionality). Neurocognitive studies have shown that obesity and addiction are both associated with increased impulsive decision-making and attention bias in response to drug or food cues, respectively. Mirroring this, obesity and different forms of addiction seem to exhibit similar alterations in functional MRI brain activity in response to reward processing and during self-control tasks. Overall, our review provides an integrative approach to understand those facets of obesity that present similarities to addictive behaviors. In addition, we suggest that therapeutic interventions targeting inhibitory control may represent a promising approach for the prevention and/or treatment of obesity.

DRD2: Bridging the Genome and Ingestive Behavior

Recent work highlights the importance of genetic variants that influence brain structure and function in conferring risk for polygenic obesity. The neurotransmitter dopamine (DA) has a pivotal role in energy balance by integrating metabolic signals with circuits supporting cognitive, perceptual, and appetitive functions that guide feeding. It has also been established that diet and obesity alter DA signaling, leading to compulsive-like feeding and neurocognitive impairments. This raises the possibility that genetic variants that influence DA signaling and adaptation confer risk for overeating and cognitive decline. Here, we consider the role of two common gene variants, FTO and TaqIA rs1800497 in driving gene × environment interactions promoting obesity, metabolic dysfunction, and cognitive change via their influence on DA receptor subtype 2 (DRD2) signaling.

Psychosocial Predictors of Physical Activity Change Among College Students in an Obesity Prevention Trial

BACKGROUND

Moderate-to-vigorous physical activity (MVPA) is critical for maintaining a healthy weight, although little is known about psychological barriers to maintaining MVPA in at-risk groups. Identifying characteristics associated with poor MVPA maintenance in obesity prevention programs could improve participant outcomes.

METHODS

Toward this end, we examined predictors of MVPA in an obesity prevention trial for college students at risk for weight gain (n = 333; 72% female, mean BMI = 23.4 kg/m²). Participants engaged in 1 of 3 weight control interventions and in 4 assessments over 12-month follow-up (ie, measured height/weight, self-reports of psychosocial characteristics, 4 days of accelerometer wear).

RESULTS

Multilevel modeling analyses showed that across conditions, participants decreased total MVPA minutes per week over 12 months (B = -5.48, P < .01). Baseline self-report scores for both impulsiveness and cognitive dissonance regarding engaging in unhealthy behaviors negatively predicted MVPA over time. Participants higher (vs. lower) in baseline impulsiveness (B = -6.89, P = .03) and dissonance (B = -4.10, P = .04) began the study with more MVPA minutes, but showed sharper declines over time.

CONCLUSIONS

Targeted MVPA-focused intervention for students who show elevated impulsiveness and cognitive dissonance may improve both MVPA and weight control outcomes for these individuals.

Identification and regulation of emotions in adults of varying weight statuses

Comparing individuals of varying weight statuses on their identification and regulation of emotions may increase our understanding of mechanisms that drive excess weight gain and highlight more precise weight regulation targets. In Study I ( N = 1333), adults with obesity had reduced self-reported attention to and repair of emotions compared to adults with overweight or normal weight. In Study II ( N = 85), adults with obesity had deficits in assessor-administrated tasks of strategic emotional intelligence (i.e. understanding and using emotional information for self-management). Problems identifying and regulating emotions could impact emotion regulation processes that lead to problematic behaviors associated with eating and weight gain.

Reorganization of brain connectivity in obesity

Global brain connectivity (GBC) identifies regions of the brain, termed "hubs," which are densely connected and metabolically costly, and have a wide influence on brain function. Since obesity is associated with central and peripheral metabolic dysfunction we sought to determine if GBC is altered in obesity. Two independent fMRI data sets were subjected to GBC analyses. The first data set was acquired while participants (n = 15 healthy weight and 15 obese) tasted milkshake and the second with participants at rest (n = 33 healthy weight and 28 obese). In the resting state and during milkshake consumption GBC is consistently decreased in the ventromedial and ventrolateral prefrontal cortex, insula and caudate nucleus, and increased in brain regions belonging to the dorsal attention network including premotor areas, superior parietal lobule, and visual cortex. During milkshake consumption, but not at rest, additional decreases in GBC are observed in feeding-related circuitry including the insula, amygdala, anterior hippocampus, hypothalamus, midbrain, brainstem and somatomotor cortex. Additionally, GBC differences were not accounted for by age. These results demonstrate that obesity is associated with decreased GBC in prefrontal and feeding circuits and increased GBC in the dorsal attention network. We therefore conclude that global brain organization is altered in obesity to favor networks important for external orientation over those monitoring homeostatic state and guiding feeding decisions. Furthermore, since prefrontal decreases are also observed at rest in obese individuals future work should evaluate whether these changes are associated with neurocognitive impairments frequently observed in obesity and diabetes. Hum Brain Mapp 38:1403-1420, 2017. © 2016 Wiley Periodicals, Inc.

Dietary Restraint Partially Mediates the Relationship between Impulsivity and Binge Eating Only in Lean Individuals: The Importance of Accounting for Body Mass in Studies of Restraint

Binge eating is characteristic of eating and weight-related disorders such as binge eating disorder, bulimia nervosa, and obesity. In light of data suggest impulsivity is associated with overeating specifically in restrained eaters, this study sought to elucidate the exact nature of the associations between these variables, hypothesizing that the relationship between impulsivity and binge eating is mediated by restrained eating. We further hypothesized that the role of dietary restraint as a mediator would be moderated by body mass index (BMI). Study participants (n = 506, 50.6% female) were categorized based on self-reported BMI as under- and normal-weight (BMI < 25, 65.8%, n = 333) or overweight and obese (BMI ≥ 25, 34.2%, n = 173) and completed the “restrained eating” subscale of the Dutch Eating Behavior Questionnaire, the “impulse control difficulties” subscale of the Difficulties with Emotion Regulation Scale, and the Binge Eating Scale. Findings provide initial evidence for the hypothesized moderated mediation model, with dietary restraint partially mediating the relationship between impulsivity and binge eating severity only in lean respondents. In respondents with overweight or obesity, impulsivity was significantly correlated with binge eating severity, but not with dietary restraint. Findings inform our conceptualization of dietary restraint as a possible risk factor for binge eating and highlight the importance of accounting for body mass in research on the impact of dietary restraint on eating behaviors.

Maternal high-fat diet and obesity impact palatable food intake and dopamine signaling in nonhuman primate offspring

OBJECTIVE

To utilize a nonhuman primate model to examine the impact of maternal high-fat diet (HFD) consumption and pre-pregnancy obesity on offspring intake of palatable food and to examine whether maternal HFD consumption impaired development of the dopamine system, critical for the regulation of hedonic feeding.

METHODS

The impact of exposure to maternal HFD and obesity on offspring consumption of diets of varying composition was assessed after weaning. The influence of maternal HFD consumption on the development of the prefrontal cortex-dopaminergic system at 13 months of age was also examined.

RESULTS

During a preference test, offspring exposed to maternal HFD consumption and obesity displayed increased intake of food high in fat and sugar content relative to offspring from lean control mothers. Maternal HFD consumption suppressed offspring dopamine signaling (as assessed by immunohistochemistry) relative to control offspring. Specifically, there was decreased abundance of dopamine fibers and of dopamine receptor 1 and 2 proteins.

CONCLUSIONS

This study reveals that offspring exposed to both maternal HFD consumption and maternal obesity during early development are at increased risk for obesity due to overconsumption of palatable energy-dense food, a behavior that may be related to reduced central dopamine signaling.

New data on psychological traits and sleep profiles of patients affected by nocturnal eating

OBJECTIVE

Nocturnal eating behavior is shared by patients affected by a parasomnia, sleep-related eating disorder (SRED), and several eating disorders such as night eating syndrome (NES) and binge-eating disorder (BED); however, the differential clinical features of these patients have been poorly studied, with persisting difficulties in defining the borders between these pathologies. The aim of this study was to evaluate polysomnographic and personality characteristics of nocturnal eaters to further differentiate the syndromes.

METHODS

During a period of six months, consecutive patients complaining of nocturnal eating were asked to participate to the study. Twenty-four patients who were found to eat during the polysomnographic recording (PSG) study, and gender-matched control subjects were included. All subjects underwent a full-night video-PSG study and a psychometric assessment including the Eating Disorder Inventory (EDI-2), the self-rating Bulimic Investigatory Test-Edinburgh (BITE), the Temperament and Character Inventory (TCI), and the Barratt Impulsivity Scale (BIS).

RESULTS

Nocturnal eaters showed a mild reduction in sleep efficiency and duration due to a moderate sleep fragmentation, whereas the percentage of each sleep stage was not significantly affected. Nocturnal eaters scored higher at many subscales of the EDI-2, at the BITE symptoms subscale, and at the BIS attentional impulsivity subscale.

CONCLUSION

The psychological characteristics found in our patients with NES seem to be typical for patients affected by eating disorders, and support the hypothesis that the nocturnal behavior of these individuals is due to an eating disorder; however, specific traits also allow differentiation of NES from BED.

Working memory and reward association learning impairments in obesity

Obesity has been associated with impaired executive functions including working memory. Less explored is the influence of obesity on learning and memory. In the current study we assessed stimulus reward association learning, explicit learning and memory and working memory in healthy weight, overweight and obese individuals. Explicit learning and memory did not differ as a function of group. In contrast, working memory was significantly and similarly impaired in both overweight and obese individuals compared to the healthy weight group. In the first reward association learning task the obese, but not healthy weight or overweight participants consistently formed paradoxical preferences for a pattern associated with a negative outcome (fewer food rewards). To determine if the deficit was specific to food reward a second experiment was conducted using money. Consistent with Experiment 1, obese individuals selected the pattern associated with a negative outcome (fewer monetary rewards) more frequently than healthy weight individuals and thus failed to develop a significant preference for the most rewarded patterns as was observed in the healthy weight group. Finally, on a probabilistic learning task, obese compared to healthy weight individuals showed deficits in negative, but not positive outcome learning. Taken together, our results demonstrate deficits in working memory and stimulus reward learning in obesity and suggest that obese individuals are impaired in learning to avoid negative outcomes.

Dysfunctional involvement of emotion and reward brain regions on social decision making in excess weight adolescents

Obese adolescents suffer negative social experiences, but no studies have examined whether obesity is associated with dysfunction of the social brain or whether social brain abnormalities relate to disadvantageous traits and social decisions. We aimed at mapping functional activation differences in the brain circuitry of social decision making in adolescents with excess versus normal weight, and at examining whether these separate patterns correlate with reward/punishment sensitivity, disordered eating features, and behavioral decisions. In this fMRI study, 80 adolescents aged 12 to 18 years old were classified in two groups based on age adjusted body mass index (BMI) percentiles: normal weight (n = 44, BMI percentiles 5th-84th) and excess weight (n = 36, BMI percentile ≥ 85th). Participants were scanned while performing a social decision-making task (ultimatum game) in which they chose to "accept" or "reject" offers to split monetary stakes made by another peer. Offers varied in fairness (Fair vs. Unfair) but in all cases "accepting" meant both players win the money, whereas "rejecting" meant both lose it. We showed that adolescents with excess weight compared to controls display significantly decreased activation of anterior insula, anterior cingulate, and midbrain during decisions about Unfair versus Fair offers. Moreover, excess weight subjects show lower sensitivity to reward and more maturity fears, which correlate with insula activation. Indeed, blunted insula activation accounted for the relationship between maturity fears and acceptance of unfair offers. Excess weight adolescents have diminished activation of brain regions essential for affective tracking of social decision making, which accounts for the association between maturity fears and social decisions.

Fat mass and obesity-associated (FTO) gene polymorphisms are associated with physical activity, food intake, eating behaviors, psychological health, and modeled change in body mass index in overweight/obese Caucasian adults

The fat mass and obesity-associated (FTO) gene is currently recognized as the most robust predictor of polygenic obesity. We investigated associations between the FTO rs1421085 and rs17817449 polymorphisms and the FTO rs1421085–rs17817449 haplotype and dietary intake, eating behavior, physical activity, and psychological health, as well as the effect of these associations on BMI. N = 133 treatment seeking overweight/obese Caucasian adults participated in this study. Genotyping was performed from whole blood samples. Weight and height was measured and a non-quantified food frequency questionnaire was completed to assess food group intake. Validated questionnaires were completed to assess physical activity (Baecke questionnaire), psychological health (General Health questionnaire, Rosenburg self-esteem scale and Beck Depression Inventory), and eating behavior (Three Factor Eating questionnaire). The risk alleles of the FTO polymorphisms were associated with poorer eating behaviors (higher hunger, internal locus for hunger, and emotional disinhibition scores), a higher intake of high fat foods and refined starches and more depressive symptoms. The modeled results indicate that interactions between the FTO polymorphisms or haplotypes and eating behavior, psychological health, and physical activity levels may be associated with BMI. The clinical significance of these results for implementation as part of weight management interventions needs further investigation.

Examining the associations between overeating, disinhibition, and hunger in a nonclinical sample of college women

BACKGROUND

Binge eating (BE) has long been identified as a correlate of overweight and obesity. However, less empirical attention has been given to overeating with and without loss of control (LOC) in nonclinical samples.

PURPOSE

The goal of the present study was to examine the association of (1) established correlates of BE, namely, weight and shape concerns, dietary restraint, and negative affect, and (2) three additional correlates, disinhibition, hunger, and interoceptive awareness (IA), to overeating in a nonclinical sample of college women.

METHOD

Female students (n = 1,447) aged 18 to 21 years recruited from colleges in three Canadian metropolitan areas completed self-report questionnaires in class to assess sociodemographic and anthropomorphic characteristics, overeating, LOC, dietary restraint, negative affect, weight and shape concerns, IA, disinhibition, and hunger.

RESULTS

The established correlates of BE were significant correlates of all types of overeating and explained 33 % of the variance. Disinhibition was the most strongly associated correlate of overeating.

CONCLUSIONS

Findings suggest that established correlates of BE are associated with other types of overeating such as objective overeating (OOE), as are disinhibition and hunger.

Sex chromosome complement influences operant responding for a palatable food in mice

The procurement and consumption of palatable, calorie-dense foods is influenced by the nutritional and hedonic value of foods. Although many factors can influence the control over behavior by foods rich in sugar and fat, emerging evidence indicates that biological sex may play a particularly crucial role in the types of foods individuals seek out, as well as the level of motivation individuals will exert to obtain those foods. However, a systematic investigation of food-seeking and consumption that disentangles the effects of the major sex-biasing factors, including sex chromosome complement and organizational and activational effects of sex hormones, has yet to be conducted. Using the four core genotypes mouse model system, we separated and quantified the effects of sex chromosome complement and gonadal sex on consumption of and motivation to obtain a highly palatable solution [sweetened condensed milk (SCM)]. Gonadectomized mice with an XY sex chromosome complement, compared with those with two X chromosomes, independent of gonadal sex, appeared to be more sensitive to the reward value of the SCM solution and were more motivated to expend effort to obtain it, as evidenced by their dramatically greater expended effort in an instrumental task with progressively larger response-to-reward ratios. Gonadal sex independently affected free consumption of the solution but not motivation to obtain it. These data indicate that gonadal and chromosomal sex effects independently influence reward-related behaviors, contributing to sexually dimorphic patterns of behavior related to the pursuit and consumption of rewards.

Food-independent tendency to disadvantageous decisions in obese individuals with regular binge eating

OBJECTIVE

The objective of this study was to explore whether or not obese patients with and without regular binge eating differ with regard to their decision-making abilities.

METHODS

Decision-making was measured by using a computerized version of the Iowa Gambling task (IGT) in 34 obese patients with regular binge eating (BE(+)) and 34 obese individuals without binge eating (BE(-)) matched for age and sex. In addition, computerized versions of the Auditory Verbal Learning Test and the Corsi Block Tapping Test were administered. Participants further answered questionnaires concerning eating disorder symptoms (Eating Disorder Examination-Questionnaire) and depression (Patient Health Questionnaire depression scale).

RESULTS

The BE(+) group reported more eating disorder and depressive symptoms than the BE(-) group but did not differ with regard to BMI, working memory deficits, depressive symptoms, somatic comorbidity (i.e., hypertension, diabetes, sleep apnea, hyperlipidemia, pain disorder), or education. Binge eating participants showed poorer decision-making abilities based on the total IGT net scores. However, they did not differ from those without regular binge eating in improving their choice behavior over the task.

CONCLUSIONS

The group difference in total IGT net scores suggests more general, food-independent decision making problems in obese individuals with regular binge eating compared to those without. Treatment of obese patients with BED could be enhanced by training them to better control risky decisions, to delay gratification in an effortful way and to activate appropriate alternative behaviors.

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.

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.

Maternal pre-pregnancy body mass index and internalizing and externalizing problems in offspring

OBJECTIVE

To determine if maternal pre-pregnancy body mass index (BMI) is associated with increased levels of internalizing and externalizing symptomatology in offspring throughout childhood and adolescence, and if these links persist after adjusting for the confounders of these associations.

METHOD

We examined links between maternal pre-pregnancy BMI and internalizing and externalizing symptoms in the offspring of 2785 members of the Western Australian Pregnancy (Raine) Cohort. Mothers rated these problems using the Child Behavior Checklist when their children were 5, 8, 10, 14, and 17 years of age. Growth curves were generated using multilevel linear regression to examine associations and to determine if changes in levels of these symptoms varied over time by maternal BMI.

RESULTS

Increased maternal pre-pregnancy BMI was associated with stably elevated levels of externalizing problems, and exhibited a statistically significant interaction with internalizing problems over time, indicating that youth born to mothers with higher maternal pre-pregnancy BMIs had less rapid decreases in internalizing scores as they got older. Significant positive associations between maternal pre-pregnancy BMI and elevated levels of internalizing problems emerged at age 8 and increased through 17. These findings persisted despite adjustment for confounders.

CONCLUSIONS

Exposure to elevated maternal pre-pregnancy BMI is associated with increased levels of internalizing and externalizing problems throughout childhood and adolescence. Further work is required to establish if these associations are causal. If elevated maternal pre-pregnancy BMI is causally linked to psychopathology in offspring, it could provide a potentially realizable target for the prevention of mental health problems in youth.

Functional brain imaging of appetite

Obesity is a neurobehavioral disorder that results from a combination of overeating and insufficient physical activity. Finely tuned mechanisms exist to match food intake to caloric expenditure. However, faced with abundant inexpensive and calorie-dense foods, many humans (and perhaps most) have a tendency to consume beyond their caloric needs. The brain controls food intake by sensing internal energy-balance signals and external cues of food availability, and by controlling feeding behavior; it is therefore at the centre of the obesity problem. This article reviews the recent use of functional brain imaging in humans to study the neural control of appetite, and how the neural systems involved may cause vulnerability to overeating in the obesogenic environment.

Habituation to the pleasure elicited by sweetness in lean and obese women

In this study, we used a validated psychophysical tool, the hedonic general magnitude scale (hedonic gLMS), to examine whether hedonic responsivity after repetitive tasting of a sweet-tasting liquid follows a habituation pattern that is independent of adaptation to the sweet taste at the orosensory level, and whether the pattern of response is different between obese (N=22) and lean (N=32) women. The perceived sweet intensity and hedonic value of a 24% w/v sucrose solution was measured with the gLMS and sucrose preferences with the Monell two-series, forced-choice tracking method. Although women perceived the same intensity of sweetness across trials, obese women responded with a slower rate of habituation to the liking of repetitive sweet-taste orosensory stimulation than did lean women. Therefore, the decreased hedonic response observed in obese women cannot be explained by adaptation processes at the orosensory level or by differential perception of taste intensity or scale bias between the groups. The groups did not differ in the level of sweetness preferred. Because obesity was associated with slower patterns of habituation to the palatability elicited by sweetness in women, this characteristic could contribute to slower satiation rates, prolongation of eating episodes, and excessive food consumption in obese women.

A modified adjusting delay task to assess impulsive choice between isocaloric reinforcers in non-deprived male rats: effects of 5-HT₂A/C and 5-HT₁A receptor agonists

RATIONALE

Existing animal models of impulsivity frequently use food restriction to increase subjects' motivation. In addition, behavioral tasks that assess impulsive choice typically involve the use of reinforcers with dissimilar caloric content. These factors represent energy-homeostasis limitations, which may confound the interpretation of results and limit the applicability of these models.

OBJECTIVES

This study was aimed at validating face and convergent validities of a modified adjusting delay task, which assesses impulsive choice between isocaloric reinforcers in ad libitum fed rats.

METHODS

Male Wistar rats (n = 18) were used to assess the preferredness and reinforcing efficacy of a "supersaccharin" solution (1.5% glucose/0.4% saccharin) over a 1.5% glucose solution. A separate group of rats (n = 24) was trained in a modified adjusting delay task, which involved repeated choice between the glucose solution delivered immediately and the supersaccharin solution delivered after a variable delay. To pharmacologically validate the task, the effects of the 5-HT(2A/C) receptor agonist (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane [(±)-DOI] and the 5-HT(1A) receptor agonist (±)-8-hydroxy-2-(dipropylamino)tetralin hydrobromide [(±)-8-OH-DPAT] on impulsive choice were then evaluated.

RESULTS

Supersaccharin was highly reinforcing and uniformly preferred over the glucose solution by all subjects. Rats quickly learned the task, and impulsivity was a very stable and consistent trait. DOI and 8-OH-DPAT significantly and dose dependently increased impulsive choice in this modified adjusting delay task.

CONCLUSIONS

We validated a rodent task of impulsive choice, which eliminates typical energy-homeostasis limitations and, therefore, opens new avenues in the study of impulsivity in preclinical feeding and obesity research.

Feeding and reward: perspectives from three rat models of binge eating

Research has focused on understanding how overeating can affect brain reward mechanisms and subsequent behaviors, both preclinically and in clinical research settings. This work is partly driven by the need to uncover the etiology and possible treatments for the ongoing obesity epidemic. However, overeating, or non-homeostatic feeding behavior, can occur independent of obesity. Isolating the variable of overeating from the consequence of increased body weight is of great utility, as it is well known that increased body weight or obesity can impart its own deleterious effects on physiology, neural processes, and behavior. In this review, we present data from three selected animal models of normal-weight non-homeostatic feeding behavior that have been significantly influenced by Bart Hoebel's 40+-yr career studying motivation, feeding, reinforcement, and the neural mechanisms that participate in the regulation of these processes. First, a model of sugar bingeing is described (Avena/Hoebel), in which animals with repeated, intermittent access to a sugar solution develop behaviors and brain changes that are similar to the effects of some drugs of abuse, serving as the first animal model of food addiction. Second, another model is described (Boggiano) in which a history of dieting and stress can perpetuate further binge eating of palatable and non-palatable food. In addition, a model (Boggiano) is described that allows animals to be classified as having a binge-prone vs. binge-resistant behavioral profile. Lastly, a limited access model is described (Corwin) in which non-food deprived rats with sporadic limited access to a high-fat food develop binge-type behaviors. These models are considered within the context of their effects on brain reward systems, including dopamine, the opioids, cholinergic systems, serotonin, and GABA. Collectively, the data derived from the use of these models clearly show that behavioral and neuronal consequences of bingeing on a palatable food, even when at a normal body weight, are different from those that result from simply consuming the palatable food in a non-binge manner. These findings may be important in understanding how overeating can influence behavior and brain chemistry.

Is bigger better? Macrosomia and psychopathology later in life

Evidence suggests that a curvilinear relationship may exist between birth weight and later psychopathology. Increases in the prevalence of macrosomia and of two of its risk factors (maternal pre-pregnancy obesity and diabetes mellitus) and their amenability to intervention argue for a critical review of the association between macrosomia and mental illness. Of the nine studies in adults and six studies in youth that have examined associations between macrosomia and psychiatric disorders, seven have provided evidence suggestive of a link. Significant methodological variability and an inability to adjust for important confounders limit the findings of these studies. As a result, it remains unclear if individuals born macrosomic are at increased risk for psychopathology later in life. Future work should attempt to examine a broader range of psychiatric outcomes, use validated measures, include data on putative confounders and utilize genetically sensitive designs to assess associations between macrosomia, its precursors and later psychological and emotional functioning.

Psychological correlates of childhood obesity

To enhance the prevention and intervention efforts of childhood obesity, there is a strong need for the early detection of psychological factors contributing to its development and maintenance. Rather than a stable condition, childhood obesity represents a dynamic process, in which behavior, cognition and emotional regulation interact mutually with each other. Family structure and context, that is, parental and familial attitudes, activity, nutritional patterns as well as familial stress, have an important role with respect to the onset and maintenance of overweight and obesity. Behavioral and emotional problems are found in many, though not all, obese children, with a higher prevalence in clinical, treatment-seeking samples. The interrelatedness between obesity and psychological problems seems to be twofold, in that clinically meaningful psychological distress might foster weight gain and obesity may lead to psychosocial problems. The most frequently implicated psychosocial factors are externalizing (impulsivity and attention-deficit hyperactivity disorder) and internalizing (depression and anxiety) behavioral problems and uncontrolled eating behavior. These findings strengthen the need to further explore the interrelatedness between psychological problems and childhood obesity.

Canadian youth born large or small for gestational age and externalizing and internalizing problems

OBJECTIVE

To determine if youth born large for gestational age (LGA; birth weight above the 95th percentile) or small for gestational age (SGA; less than the fifth percentile) are at an increased risk of developing symptoms of externalizing and internalizing problems.

METHOD

Data on members of the Ontario Child Health Study aged 4 to 16 years were used to examine associations between LGA, SGA, and psychopathology. This sample consisted of 2923 youth about whom parent, teacher, and self-reported levels of internalizing and externalizing symptoms were available, and whose caregivers retrospectively reported birth weight and gestational age (GA). Psychopathology was assessed using the Diagnostic and Statistical Manual of Mental Disorders-oriented scales derived from the Child Behavior Checklist.

RESULTS

Multilevel linear regression analyses revealed that after adjustment for parental psychopathology, socioeconomic disadvantage, sex, age, maternal age, birth order, and child health and school performance, youth born LGA had higher scores on the self-reported externalizing scale (1.39, 95% CI 0.01 to 2.78), but not internalizing scale, compared with youth born at an appropriate weight for GA (10th to 90th percentile). Parent and teacher ratings generally supported these findings in direction but did not reach statistical significance. Youth and parents reported increased levels of externalizing and internalizing symptoms in youth born SGA, but these were not statistically significant.

CONCLUSIONS

Youth born above the 95th percentile for GA manifest increased levels of externalizing symptoms. Given increasing rates of macrosomic births, further study is warranted to replicate and determine the clinical significance of these findings, the contribution of the antecedents of LGA to this risk and the extent to which this association may be causal.

The emerging link between alcoholism risk and obesity in the United States

CONTEXT

The prevalence of obesity has risen sharply in the United States in the past few decades. Etiologic links between obesity and substance use disorders have been hypothesized.

OBJECTIVE

To determine whether familial risk of alcohol dependence predicts obesity and whether any such association became stronger between the early 1990s and early 2000s.

DESIGN

We conducted analyses of the repeated cross-sectional National Longitudinal Alcohol Epidemiologic Survey (1991-1992) and National Epidemiologic Survey on Alcohol and Related Conditions (2001-2002).

SETTING

The noninstitutionalized US adult population in 1991-1992 and 2001-2002.

PARTICIPANTS

Individuals drawn from population-based, multistage, random samples (N = 39 312 and 39 625).

MAIN OUTCOME MEASURE

Obesity, defined as a body mass index (calculated from self-reported data as weight in kilograms divided by height in meters squared) of 30 or higher and predicted from family history of alcoholism and/or problem drinking.

RESULTS

In 2001-2002, women with a family history of alcoholism (defined as having a biological parent or sibling with a history of alcoholism or alcohol problems) had 49% higher odds of obesity than those without a family history (odds ratio, 1.48; 95% confidence interval, 1.36-1.61; P < .001), a highly significant increase (P < .001) from the odds ratio of 1.06 (95% confidence interval, 0.97-1.16) estimated for 1991-1992. For men in 2001-2002, the association was significant (odds ratio, 1.26; 95% confidence interval, 1.14-1.38; P < .001) but not as strong as for women. The association and the secular trend for women were robust after adjustment for covariates, including sociodemographic variables, smoking status, alcohol use, alcohol or drug dependence, and major depression. Similar trends were observed for men but did not meet statistical significance criteria after adjustment for covariates.

CONCLUSIONS

These results provide epidemiologic support for a link between familial alcoholism risk and obesity in women and possibly in men. This link has emerged in recent years and may result from an interaction between a changing food environment and predisposition to alcoholism and related disorders.

Obesity, orbitofrontal structure and function are associated with food choice: a cross-sectional study

Objectives Obesity is on the rise in the US and is linked to the development of type 2 diabetes and cardiovascular disease. Emerging evidence over the last decade suggests that obesity may also adversely affect executive function and brain structure. Although a great deal of research focuses on how diet affects the brain and cognitive performance, no study focuses on how food choice may be associated with brain integrity. Here we investigated how lean and overweight/obese (o/o) adults differed in their food choices and how brain structure and cognition may be associated with those choices. Design As part of an ongoing study on diabetes and the brain, participants had routine blood work and a research MRI, received a battery of neurocognitive tests, and were instructed to keep a 3-day food diary. Results and conclusions The lean group ate more high quality foods and less low quality foods compared to the o/o group. In the o/o group, high quality food choices were associated with orbitofrontal cortex volume. The lean group performed better than the o/o group on neurocognitive measures of executive function, such as the Stroop Interference Test, the Wisconsin Card Sort Test and the Trail Making Test B-A, and on attention and concentration tasks such as the Digit Symbol Substitution Test. Taken together, these preliminary data suggest that in obesity poor food choices may be associated with frontal cognitive impairments that may be the result of, or contribute to, decreases in orbitofrontal cortex volume. Therefore, longitudinal studies are warranted to investigate a causal link between food choice and executive functioning.

Response style and vulnerability to anger-induced eating in obese adults

Emotional eating appears to contribute to weight gain, but the characteristics that make one vulnerable to emotional eating remain unclear. The present study examined whether two negative affect response styles, rumination and distraction, influenced palatable food intake following an anger mood induction in normal weight and obese adults. We hypothesized that higher rumination and lower distraction would be associated with greater vulnerability to anger-induced eating, particularly among obese individuals. Sixty-one participants (74% female, mean age=34.6) underwent neutral and anger mood inductions in counterbalanced order. Directly following each mood induction, participants were provided with 2400 kcal of highly palatable snack foods in the context of a laboratory taste test. Results revealed that distraction influenced energy intake following the mood induction for obese but not normal weight individuals. Obese participants who reported greater use of distraction strategies consumed fewer calories than those reporting less use of distraction strategies. These findings were independent of subjective hunger levels, individual differences in mood responses and trait anger, and other factors. Rumination did not account for changes in energy intake among obese or normal weight participants. Among obese individuals, the tendency to utilize fewer negative affect distraction strategies appears to be associated with vulnerability to eating in response to anger. Future research should determine whether coping skills training can reduce emotional eating tendencies.

Bromocriptine increased operant responding for high fat food but decreased chow intake in both obesity-prone and resistant rats

Dopamine (DA) and DA D₂ receptors (D2R) have been implicated in obesity and are thought to be involved in the rewarding properties of food. Osborne-Mendel (OM) rats are susceptible to diet induced obesity (DIO) while S5B/P (S5B) rats are resistant when given a high-fat diet. Here we hypothesized that the two strains would differ in high-fat food self-administration (FSA) and that the D2R agonist bromocriptine (BC) would differently affect their behavior. Ad-libitum fed OM and S5B/P rats were tested in a FSA operant chamber and were trained to lever press for high-fat food pellets under a fixed-ratio (FR1) and a progressive ratio (PR) schedule. After sixteen days of PR sessions, rats were treated with three different doses of BC (1, 10 and 20 mg/kg). No significant differences were found between the two strains in the number of active lever presses. BC treatment (10 mg/kg and 20 mg/kg) increased the number of active lever presses (10 mg/kg having the strongest effect) whereas it decreased rat chow intake in the home cage with equivalent effects in both strains. These effects were not observed on the day of BC administration but on the day following its administration. Our results suggest that these two strains have similar motivation for procuring high fat food using this paradigm. BC increased operant responding for high-fat pellets but decreased chow intake in both strains, suggesting that D2R stimulation may have enhanced the motivational drive to procure the fatty food while correspondingly decreasing the intake of regular food. These findings suggest that susceptibility to dietary obesity (prior to the onset of obesity) may not affect operant motivation for a palatable high fat food and that differential susceptibility to obesity may be related to differential sensitivity to D2R stimulation.

Managing the pandemic of obesity: siding with the fox or the hedgehog?

Obesity is a major public health problem of pandemic proportion. Despite its high prevalence and widespread distribution (consistent with a common underlying etiology), clinical psychologists and primary care physicians routinely approach the problem with individualized but often ineffective treatments like psychotherapy and pharmacotherapy, or propose alterations to specific components of the 'toxic environment', cultural influences, and psychosocial factors purported to cause overeating. This paper presents an alternative perspective and proposes a potential framework for assisting health professionals in developing rational approaches to education about and preventive treatment of obesity based on the role of factors in early life that contribute to personality and behavior and which over time lead to obesity and its maintenance.