Body mass correlates inversely with inhibitory control in response to food among adolescent girls: an fMRI study

Ginseng and Ginkgo Biloba Effects on Cognition as Modulated by Cardiovascular Reactivity: A Randomised Trial

Background

There is some evidence to suggest that ginseng and Ginkgo biloba can improve cognitive performance, however, very little is known about the mechanisms associated with such improvement. Here, we tested whether cardiovascular reactivity to a task is associated with cognitive improvement.

Methodology/Principal findings

Using a double-blind, placebo controlled, crossover design, participants (N = 24) received two doses of Panax Ginseng (500, 1000 mg) or Ginkgo Biloba (120, 240 mg) (N = 24), and underwent a series of cognitive tests while systolic, diastolic, and heart rate readings were taken. Ginkgo Biloba improved aspects of executive functioning (Stroop and Berg tasks) in females but not in males. Ginseng had no effect on cognition. Ginkgo biloba in females reversed the initial (i.e. placebo) increase in cardiovascular reactivity (systolic and diastolic readings increased compared to baseline) to cognitive tasks. This effect (reversal) was most notable after those tasks (Stroop and Iowa) that elicited the greatest cardiovascular reactivity during placebo. In males, although ginkgo also decreased cardiovascular readings, it did so from an initial (placebo) blunted response (i.e. decrease or no change from baseline) to cognitive tasks. Ginseng, on the contrary, increased cardiovascular readings compared to placebo.

Conclusions/Significance

These results suggest that cardiovascular reactivity may be a mechanism by which ginkgo but not ginseng, in females is associated with certain forms of cognitive improvement.

Trial Registration

ClinicalTrials.gov NCT02386852

Impulsivity-based thrifty eating phenotype and the protective role of n-3 PUFAs intake in adolescents

The goal of the present study was to investigate whether intrauterine growth restriction (IUGR) affects brain responses to palatable foods and whether docosahexaenoic acid (DHA, an omega-3 fatty acid that is a primary structural component of the human brain) serum levels moderate the association between IUGR and brain and behavioral responses to palatable foods. Brain responses to palatable foods were investigated using a functional magnetic resonance imaging task in which participants were shown palatable foods, neutral foods and non-food items. Serum DHA was quantified in blood samples, and birth weight ratio (BWR) was used as a proxy for IUGR. The Dutch Eating Behavior Questionnaire (DEBQ) was used to evaluate eating behaviors. In the contrast palatable food > neutral items, we found an activation in the right superior frontal gyrus with BWR as the most important predictor; the lower the BWR (indicative of IUGR), the greater the activation of this region involved in impulse control/decision making facing the viewing of palatable food pictures versus neutral items. At the behavioral level, a general linear model predicting external eating using the DEBQ showed a significant interaction between DHA and IUGR status; in IUGR individuals, the higher the serum DHA, the lower is external eating. In conclusion, we suggest that IUGR moderates brain responses when facing stimuli related to palatable foods, activating an area related to impulse control. Moreover, higher intake of n-3 PUFAs can protect IUGR individuals from developing inappropriate eating behaviors, the putative mechanism of protection would involve decreasing intake in response to external food cues in adolescents/young adults.

An obesity-associated risk allele within the FTO gene affects human brain activity for areas important for emotion, impulse control and reward in response to food images

Understanding how genetics influences obesity, brain activity and eating behaviour will add important insight for developing strategies for weight-loss treatment, as obesity may stem from different causes and as individual feeding behaviour may depend on genetic differences. To this end, we examined how an obesity risk allele for the FTO gene affects brain activity in response to food images of different caloric content via functional magnetic resonance imaging (fMRI). Thirty participants homozygous for the rs9939609 single nucleotide polymorphism were shown images of low- or high-calorie food while brain activity was measured via fMRI. In a whole-brain analysis, we found that people with the FTO risk allele genotype (AA) had increased activity compared with the non-risk (TT) genotype in the posterior cingulate, cuneus, precuneus and putamen. Moreover, higher body mass index in the AA genotype was associated with reduced activity to food images in areas important for emotion (cingulate cortex), but also in areas important for impulse control (frontal gyri and lentiform nucleus). Lastly, we corroborate our findings with behavioural scales for the behavioural inhibition and activation systems. Our results suggest that the two genotypes are associated with differential neural processing of food images, which may influence weight status through diminished impulse control and reward processing.

Differential effects of hunger and satiety on insular cortex and hypothalamic functional connectivity

The insula cortex and hypothalamus are implicated in eating behaviour, and contain receptor sites for peptides and hormones controlling energy balance. The insula encompasses multi‐functional subregions, which display differential anatomical and functional connectivities with the rest of the brain. This study aimed to analyse the effect of fasting and satiation on the functional connectivity profiles of left and right anterior, middle, and posterior insula, and left and right hypothalamus. It was hypothesized that the profiles would be altered alongside changes in homeostatic energy balance. Nineteen healthy participants underwent two 7‐min resting state functional magnetic resonance imaging scans, one when fasted and one when satiated. Functional connectivity between the left posterior insula and cerebellum/superior frontal gyrus, and between left hypothalamus and inferior frontal gyrus was stronger during fasting. Functional connectivity between the right middle insula and default mode structures (left and right posterior parietal cortex, cingulate cortex), and between right hypothalamus and superior parietal cortex was stronger during satiation. Differences in blood glucose levels between the scans accounted for several of the altered functional connectivities. The insula and hypothalamus appear to form a homeostatic energy balance network related to cognitive control of eating; prompting eating and preventing overeating when energy is depleted, and ending feeding or transferring attention away from food upon satiation. This study provides evidence of a lateralized dissociation of neural responses to energy modulations.

Is it Worth the Effort? Novel Insights into Obesity-Associated Alterations in Cost-Benefit Decision-Making

Cost-benefit decision-making entails the process of evaluating potential actions according to the trade-off between the expected reward (benefit) and the anticipated effort (costs). Recent research revealed that dopaminergic transmission within the fronto-striatal circuitry strongly modulates cost-benefit decision-making. Alterations within the dopaminergic fronto-striatal system have been associated with obesity, but little is known about cost-benefit decision-making differences in obese compared with lean individuals. With a newly developed experimental task we investigate obesity-associated alterations in cost-benefit decision-making, utilizing physical effort by handgrip-force exertion and both food and non-food rewards. We relate our behavioral findings to alterations in local gray matter volume assessed by structural MRI. Obese compared with lean subjects were less willing to engage in physical effort in particular for high-caloric sweet snack food. Further, self-reported body dissatisfaction negatively correlated with the willingness to invest effort for sweet snacks in obese men. On a structural level, obesity was associated with reductions in gray matter volume in bilateral prefrontal cortex. Nucleus accumbens volume positively correlated with task induced implicit food craving. Our results challenge the common notion that obese individuals are willing to work harder to obtain high-caloric food and emphasize the need for further exploration of the underlying neural mechanisms regarding cost-benefit decision-making differences in obesity.

Imbalance in Resting State Functional Connectivity is Associated with Eating Behaviors and Adiposity in Children

Background and Hypothesis

Over the past 30 years, childhood obesity in the US has nearly doubled, while obesity has tripled among adolescents. Non-homeostatic eating, influenced by impulsivity and inhibition, may undermine successful long-term weight loss. We hypothesized that unhealthy eating habits and adiposity among children are associated with functional connectivity between brain regions associated with impulsivity, response inhibition, and reward.

Methods

We analyzed resting state functional magnetic resonance images from 38 children, ages 8–13. Using seed-based resting state functional connectivity, we quantified connectivity between brain regions associated with response inhibition (inferior parietal lobe [IPL]), impulsivity (frontal pole), and reward (nucleus accumbens [NAc]). We assessed the relationship of resting state functional connectivity with adiposity, quantified by BMI z-score, and eating behaviors, as measured by the Child Eating Behaviour Questionnaire (CEBQ). We computed an imbalance measure—the difference between [frontal pole:NAC] and [ipl:nac] functional connectivity—and investigated the relationship of this imbalance with eating behaviors and adiposity.

Results

As functional connectivity imbalance is increasingly biased toward impulsivity, adiposity increases. Similarly, as impulsivity-biased imbalance increases, food approach behaviors increase and food avoidance behaviors decrease. Increased adiposity is associated with increased food approach behaviors and decreased food avoidance behaviors.

Conclusions

In the absence of any explicit eating-related stimuli, the developing brain is primed toward food approach and away from food avoidance behavior with increasing adiposity. Imbalance in resting state functional connectivity that is associated with non-homeostatic eating develops during childhood, as early as 8–13 years of age. Our results indicate the importance of identifying children at risk for obesity for earlier intervention. In addition to changing eating habits and physical activity, strategies that normalize neural functional connectivity imbalance are needed to maintain healthy weight. Mindfulness may be one such approach as it is associated with increased response inhibition and decreased impulsivity.

Reward-related decision making in eating and weight disorders: A systematic review and meta-analysis of the evidence from neuropsychological studies

Eating disorders (EDs) and overweight/obesity (OW/OB) are serious public health concerns that share common neuropsychological features and patterns of disturbed eating. Reward-related decision making as a basic neurocognitive function may trans-diagnostically underlie both pathological overeating and restricted eating. The present meta-analysis synthesizes the evidence from N=82 neuropsychological studies for altered reward-related decision making in all ED subtypes, OW and OB. The overall effect sizes for the differences between currently-ill ED patients and OW/OB people and controls were Hedge's g=-0.49 [CI: -0.63; -0.35], and Hedge's g=-0.39 [CI: -0.53; -0.25], respectively. Decision making was found to be altered to similar degrees in all ED subtypes and OB. Effect sizes, however, diverged for the different measures of decision making. Adolescents appear to be less affected than adults. When foods were used as rewarding stimuli, decision making was found to be intact in OB. The findings support that altered general reward-related decision making is a salient neuropsychological factor across eating and weight disorders in adulthood.

The Biggest Loser Thinks Long-Term: Recency as a Predictor of Success in Weight Management

Only a minority of participants in behavioral weight management lose weight significantly. The ability to predict who is likely to benefit from weight management can improve the efficiency of obesity treatment. Identifying predictors of weight loss can also reveal potential ways to improve existing treatments. We propose a neuro-psychological model that is focused on recency: the reliance on recent information at the expense of time-distant information. Forty-four weight-management patients completed a decision-making task and their recency level was estimated by a mathematical model. Impulsivity and risk-taking were also measured for comparison. Weight loss was measured in the end of the 16-week intervention. Consistent with our hypothesis, successful dieters (n = 12) had lower recency scores than unsuccessful ones (n = 32; p = 0.006). Successful and unsuccessful dieters were similar in their demographics, intelligence, risk taking, impulsivity, and delay of gratification. We conclude that dieters who process time-distant information in their decision making are more likely to lose weight than those who are high in recency. We argue that having low recency facilitates future-oriented thinking, and thereby contributes to behavior change treatment adherence. Our findings underline the importance of choosing the right treatment for every individual, and outline a way to improve weight-management processes for more patients.

A Cognitive Profile of Obesity and Its Translation into New Interventions

Change your lifestyle: decrease your energy intake and increase your energy expenditure, is what obesity experts tell people who need to lose weight. Though the advice might be correct, it appears to be extremely difficult to change one’s lifestyle. Unhealthy habits usually are ingrained and hard to change, especially for people with an “obese cognitive profile.” Knowledge of the cognitive mechanisms that maintain unhealthy eating habits is necessary for the development of interventions that can change behavior effectively. This paper discusses some cognitive processes that might maintain unhealthy eating habits and make healthier eating difficult, like increased food cue reactivity, weak executive skills and attention bias. An effort is also done to translate these basic scientific findings into new interventions which aim to tackle the sabotaging cognitive processes. Preliminary studies into the effectiveness of these interventions, if available, are presented.

Developmental programming by maternal obesity in 2015: Outcomes, mechanisms, and potential interventions

This article is part of a Special Issue "SBN 2014". Obesity in women of child-bearing age is a growing problem in developed and developing countries. Evidence from human studies indicates that maternal BMI correlates with offspring adiposity from an early age and predisposes to metabolic disease in later life. Thus the early life environment is an attractive target for intervention to improve public health. Animal models have been used to investigate the specific physiological outcomes and mechanisms of developmental programming that result from exposure to maternal obesity in utero. From this research, targeted intervention strategies can be designed. In this review we summarise recent progress in this field, with a focus on cardiometabolic disease and central control of appetite and behaviour. We highlight key factors that may mediate programming by maternal obesity, including leptin, insulin, and ghrelin. Finally, we explore potential lifestyle and pharmacological interventions in humans and the current state of evidence from animal models.

Incidental rewarding cues influence economic decisions in people with obesity

Recent research suggests that obesity is linked to prominent alterations in learning and decision-making. This general difference may also underlie the preference for immediately consumable, highly palatable but unhealthy and high-calorie foods. Such poor food-related inter-temporal decision-making can explain weight gain; however, it is not yet clear whether this deficit can be generalized to other domains of inter-temporal decision-making, for example financial decisions. Further, little is known about the stability of decision-making behavior in obesity, especially in the presence of rewarding cues. To answer these questions, obese and lean participants (n = 52) completed two sessions of a novel priming paradigm including a computerized monetary delay discounting task. In the first session, general differences between groups in financial delay discounting were measured. In the second session, we tested the general stability of discount rates. Additionally, participants were primed by affective visual cues of different contextual categories before making financial decisions. We found that the obese group showed stronger discounting of future monetary rewards than the lean group, but groups did not differ in their general stability between sessions nor in their sensitivity toward changes in reward magnitude. In the obese group, a fast decrease of subjective value over time was directly related to a higher tendency for opportunistic eating. Obese in contrast to lean people were primed by the affective cues, showing a sex-specific pattern of priming direction. Our findings demonstrate that environments rich of cues, aiming at inducing unhealthy consumer decisions, can be highly detrimental for obese people. It also underscores that obesity is not merely a medical condition but has a strong cognitive component, meaning that current dietary and medical treatment strategies may fall too short.

Gender Differences in Risk Factors for Stice’s Bulimia in a Non-Clinical Sample

Some females are at an increased risk of developing bulimia. However, etiological factors and their interplay remain controversial. The present study analyzed Sticefe Model for eating disorders in a non-clinical population by examining gender differences with respect to the following risk factors: body mass index (BMI), body dissatisfaction, perceived social pressure to be thin, body-thin internalization, and dieting behavior. A sample of 162 American college students (64 males and 91 females) was surveyed, and validated scales were used. The Sticey model was tested using Structural Equation Modeling. Our results supported Stice r Dual Pathway Model of bulimic pathology for females but not for males. Females reported significantly higher body dissatisfaction, perceived pressure to be thin and weight-loss oriented behaviors than males (p < .05), but no gender differences were found in their degree of body thin internalization (p > .05), a key predictor of body dissatisfaction (r = .33; p < .01). Participants with higher BMI reported greater social pressure to be thin than those with lower BMI (p < .05). However, females engaged in dietary restraint, the main risk factor for eating disorders, regardless of their BMI (p > .05) although their BMI was significantly lower than males (d = 0,51). The results of this study fail to support the role of BMI as a predictor of dietary restraint in females, the main risk factor of eating disorders. Males may abstain from dietary restraint to gain muscular volume and in turn increase their BMI. Implications are discussed.

Cued to Act on Impulse: More Impulsive Choice and Risky Decision Making by Women Susceptible to Overeating after Exposure to Food Stimuli

There is increasing evidence that individual differences in tendency to overeat relate to impulsivity, possibly by increasing reactivity to food-related cues in the environment. This study tested whether acute exposure to food cues enhanced impulsive and risky responses in women classified on tendency to overeat, indexed by scores on the three factor eating questionnaire disinhibition (TFEQ-D), restraint (TFEQ-R) and hunger scales. Ninety six healthy women completed two measures of impulsive responding (delayed discounting, DDT and a Go No-Go, GNG, task) and a measure of risky decision making (the balloon analogue risk task, BART) as well as questionnaire measures of impulsive behaviour either after looking at a series of pictures of food or visually matched controls. Impulsivity (DDT) and risk-taking (BART) were both positively associated with TFEQ-D scores, but in both cases this effect was exacerbated by prior exposure to food cues. No effects of restraint were found. TFEQ-D scores were also related to more commission errors on the GNG, while restrained women were slower on the GNG, but neither effect was modified by cue exposure. Overall these data suggest that exposure to food cues act to enhance general impulsive responding in women at risk of overeating and tentatively suggest an important interaction between tendency for impulsive decision making and food cues that may help explain a key underlying risk factor for overeating.

The CB1 Neutral Antagonist Tetrahydrocannabivarin Reduces Default Mode Network and Increases Executive Control Network Resting State Functional Connectivity in Healthy Volunteers

BACKGROUND

The cannabinoid cannabinoid type 1 (CB1) neutral antagonist tetrahydrocannabivarin (THCv) has been suggested as a possible treatment for obesity, but without the depressogenic side-effects of inverse antagonists such as Rimonabant. However, how THCv might affect the resting state functional connectivity of the human brain is as yet unknown.

METHOD

We examined the effects of a single 10mg oral dose of THCv and placebo in 20 healthy volunteers in a randomized, within-subject, double-blind design. Using resting state functional magnetic resonance imaging and seed-based connectivity analyses, we selected the amygdala, insula, orbitofrontal cortex, and dorsal medial prefrontal cortex (dmPFC) as regions of interest. Mood and subjective experience were also measured before and after drug administration using self-report scales.

RESULTS

Our results revealed, as expected, no significant differences in the subjective experience with a single dose of THCv. However, we found reduced resting state functional connectivity between the amygdala seed region and the default mode network and increased resting state functional connectivity between the amygdala seed region and the dorsal anterior cingulate cortex and between the dmPFC seed region and the inferior frontal gyrus/medial frontal gyrus. We also found a positive correlation under placebo for the amygdala-precuneus connectivity with the body mass index, although this correlation was not apparent under THCv.

CONCLUSION

Our findings are the first to show that treatment with the CB1 neutral antagonist THCv decreases resting state functional connectivity in the default mode network and increases connectivity in the cognitive control network and dorsal visual stream network. This effect profile suggests possible therapeutic activity of THCv for obesity, where functional connectivity has been found to be altered in these regions.

Metabolic imaging in obesity: underlying mechanisms and consequences in the whole body

Obesity is a phenotype resulting from a series of causative factors with a variable risk of complications. Etiologic diversity requires personalized prevention and treatment. Imaging procedures offer the potential to investigate the interplay between organs and pathways underlying energy intake and consumption in an integrated manner, and may open the perspective to classify and treat obesity according to causative mechanisms. This review illustrates the contribution provided by imaging studies to the understanding of human obesity, starting with the regulation of food intake and intestinal metabolism, followed by the role of adipose tissue in storing, releasing, and utilizing substrates, including the interconversion of white and brown fat, and concluding with the examination of imaging risk indicators related to complications, including type 2 diabetes, liver pathologies, cardiac and kidney diseases, and sleep disorders. The imaging modalities include (1) positron emission tomography to quantify organ-specific perfusion and substrate metabolism; (2) computed tomography to assess tissue density as an indicator of fat content and browning/ whitening; (3) ultrasounds to examine liver steatosis, stiffness, and inflammation; and (4) magnetic resonance techniques to assess blood oxygenation levels in the brain, liver stiffness, and metabolite contents (triglycerides, fatty acids, glucose, phosphocreatine, ATP, and acetylcarnitine) in a variety of organs.

Overlapping neurobehavioral circuits in ADHD, obesity, and binge eating: evidence from neuroimaging research

Attention-deficit/hyperactivity disorder (ADHD) and conditions involving excessive eating (eg, obesity, binge/loss of control eating) are increasingly prevalent within pediatric populations, and correlational and some longitudinal studies have suggested inter-relationships between these disorders. In addition, a number of common neural correlates are emerging across conditions, eg, functional abnormalities within circuits subserving reward processing and executive functioning. To explore this potential cross-condition overlap in neurobehavioral underpinnings, we selectively review relevant functional neuroimaging literature, specifically focusing on studies probing (i) reward processing, (ii) response inhibition, and (iii) emotional processing and regulation, and we outline 3 specific shared neurobehavioral circuits. Based on our review, we also identify gaps within the literature that would benefit from further research.

Impaired Early-Response Inhibition in Overweight Females with and without Binge Eating Disorder

Objective

Several studies report increased reward sensitivity towards food in overweight individuals. By contrast, data is inconclusive with respect to response inhibition in overweight individuals without binge eating disorder (BED). Hence, the latter was addressed in the present study in a group of overweight/obese females with and without BED and a normal-weight control group without eating disorders.

Method

A group of women with BED (n = 29), a group of overweight women without BED (n = 33) and normal-weight females (n = 30) participated in a pictorial priming paradigm, with food items (relevant primes) and office utensils (neutral primes) and color blobs (neutral primes) as stimuli. Increased response priming effects (i.e. priming with switches between stimulus categories) were taken as indicators of deficient behavioral inhibition.

Results

Priming effects for neutral primes were moderate and comparable across all groups. However, primes associated with the food task set lead to increased priming effects in both overweight groups. But, effects were comparable for overweight/obese participants with and without BED.

Discussion

Results suggest that early response inhibition in the context of food is impaired in overweight individuals compared to normal-weight individuals.

Altered frontal inter-hemispheric resting state functional connectivity is associated with bulimic symptoms among restrained eaters

Theory and research have indicated that restrained eating (RE) increases risk for binge-eating and eating disorder symptoms. According to the goal conflict model, such risk may result from disrupted hedonic-feeding control and its interaction with reward-driven eating. However, RE-related alterations in functional interactions among associated underlying brain regions, especially between the cerebral hemispheres, have rarely been examined directly. Therefore, we investigated inter-hemispheric resting-state functional connectivity (RSFC) among female restrained eaters (REs) (n=23) and unrestrained eaters (UREs) (n=24) following food deprivation as well as its relation to overall bulimia nervosa (BN) symptoms using voxel-mirrored homotopic connectivity (VMHC). Seed-based RSFC associated with areas exhibiting significant VMHC differences was also assessed. Compared to UREs, REs showed reduced VMHC in the dorsal-lateral prefrontal cortex (DLPFC), an area involved in inhibiting hedonic overeating. REs also displayed decreased RSFC between the right DLPFC and regions associated with reward estimation--the ventromedial prefrontal cortex (VMPFC) and posterior cingulate cortex (PCC). Finally, bulimic tendencies had a negative correlation with VMHC in the DLPFC and a positive correlation with functional connectivity (DLPFC and VMPFC) among REs but not UREs. Findings suggested that reduced inter-hemispheric functional connectivity in appetite inhibition regions and altered functional connectivity in reward related regions may help to explain why some REs fail to control hedonically-motivated feeding and experience higher associated levels of BN symptomatology.

Topical Review: Unique Contributions of Magnetic Resonance Imaging to Pediatric Psychology Research

OBJECTIVE

This review aims to provide a brief introduction of the utility of magnetic resonance imaging (MRI) methods in pediatric psychology research, describe several exemplar studies that highlight the unique benefits of MRI techniques for pediatric psychology research, and detail methods for addressing several challenges inherent to pediatric MRI research.

METHODS

Literature review.

RESULTS

Numerous useful applications of MRI research in pediatric psychology have been illustrated in published research. MRI methods yield information that cannot be obtained using neuropsychological or behavioral measures.

CONCLUSIONS

Using MRI in pediatric psychology research may facilitate examination of neural structures and processes that underlie health behaviors. Challenges inherent to conducting MRI research with pediatric research participants (e.g., head movement) may be addressed using evidence-based strategies. We encourage pediatric psychology researchers to consider adopting MRI techniques to answer research questions relevant to pediatric health and illness.

Eating behaviour in treatment-seeking obese subjects - Influence of sex and BMI classes

Obese subjects frequently show an adversely altered eating behaviour. However, little is known on differences in eating behaviour across different degree of obesity. We analysed data on the three factor eating questionnaire assessing cognitive restraint, disinhibition, and hunger that were filled in by 664 obese patients (469 women) who seeked treatment in our Interdisciplinary Obesity Center. Patients were divided in five BMI classes (30 - <35 kg/m(2), 35 - <40 kg/m(2), 40 - <50 kg/m(2), and >50 kg/m(2)). Multivariate regression analyses revealed that sex was significantly related to all three eating behaviour traits (all P < 0.042) but no significant relation to BMI (as a continuous variable) was observed. Women in comparison to men showed significantly higher cognitive restraint (9.7 ± 4.3 vs. 7.7 ± 4.4; P < 0.001) and disinhibition (9.0 ± 3.5 vs. 7.7 ± 3.5; P < 0.001) scores and also showed higher hunger scores (6.9 ± 3.7 vs. 6.3 ± 3.5; P = 0.042). Analyses on different BMI classes revealed that cognitive restraint decreased (P = 0.016) while disinhibition (P = 0.010) and hunger (P = 0.044) increased independently of sex with increasing BMI classes. However, above the obesity grade I class (i.e. BMI 30 - < 35 kg/m(2)) there were no differences in eating behaviour variables between the remaining BMI classes. Data indicate profound differences in eating behaviour between women and men that persist across a wide range of obesity. Furthermore, data suggest that while grade I obese patients show higher cognitive restraint and less disinhibition and hunger scores than more severe obese patients these dimensions of eating behaviour do not systematically vary across higher BMI classes.

Training response inhibition to food is associated with weight loss and reduced energy intake

The majority of adults in the UK and US are overweight or obese due to multiple factors including excess energy intake. Training people to inhibit simple motor responses (key presses) to high-energy density food pictures reduces intake in laboratory studies. We examined whether online response inhibition training reduced real-world food consumption and weight in a community sample of adults who were predominantly overweight or obese (N = 83). Participants were allocated in a randomised, double-blind design to receive four 10-min sessions of either active or control go/no-go training in which either high-energy density snack foods (active) or non-food stimuli (control) were associated with no-go signals. Participants' weight, energy intake (calculated from 24-h food diaries), daily snacking frequency and subjective food evaluations were measured for one week pre- and post-intervention. Participants also provided self-reported weight and monthly snacking frequency at pre-intervention screening, and one month and six months after completing the study. Participants in the active relative to control condition showed significant weight loss, reductions in daily energy intake and a reduction in rated liking of high-energy density (no-go) foods from the pre-to post-intervention week. There were no changes in self-reported daily snacking frequency. At longer-term follow-up, the active group showed significant reductions in self-reported weight at six months, whilst both groups reported significantly less snacking at one- and six-months. Excellent rates of adherence (97%) and positive feedback about the training suggest that this intervention is acceptable and has the potential to improve public health by reducing energy intake and overweight.

Prediction of daily food intake as a function of measurement modality and restriction status

OBJECTIVE

Research on eating relies on various indices (e.g., stable, momentary, neural) to accurately reflect food-related reactivity (e.g., disinhibition) and regulation (e.g., restraint) outside the laboratory. The degree to which they differentially predict real-world consumption remains unclear. Further, the predictive validity of these indices might vary depending on whether an individual is actively restricting intake.

METHODS

We assessed food craving reactivity and regulation in 46 healthy participants (30 women, 18-30 years) using standard measurements in three modalities: a) self-reported (stable) traits using surveys popular in the eating literature, and b) momentary craving ratings and c) neural activation using aggregated functional magnetic resonance imaging data gathered during a food reactivity-and-regulation task. We then used these data to predict variance in real-world consumption of craved energy-dense "target" foods across 2 weeks among normal-weight participants randomly assigned to restrict or monitor target food intake.

RESULTS

The predictive validity of four indices varied significantly by restriction. When participants were not restricting intake, momentary (B = 0.21, standard error [SE] = 0.05) and neural (B = 0.08, SE = 0.04) reactivity positively predicted consumption, and stable (B = -0.22, SE = 0.05) and momentary (B = -0.24, SE = 0.05) regulation negatively predicted consumption. When restricting, stable (B = 0.36, SE = 0.12) and neural (B = 0.51, SE = 0.12) regulation positively predicted consumption.

CONCLUSIONS

Commonly-used indices of regulation and reactivity differentially relate to an ecologically-valid eating measurement, depending on the presence of restriction goals, and thus have strong implications for predicting real-world behaviors.

Executive functioning, emotion regulation, eating self-regulation, and weight status in low-income preschool children: how do they relate?

The purpose of the present study was to examine relationships between child eating self-regulation, child non-eating self-regulation, and child BMIz in a low-income sample of Hispanic families with preschoolers. The eating in the absence of hunger task as well as parent-report of child satiety responsiveness and food responsiveness were used to assess child eating self-regulation. Two laboratory tasks assessing executive functioning, a parent questionnaire assessing child effortful control (a temperament dimension related to executive functioning), and the delay of gratification and gift delay tasks assessing child emotion regulation were used to assess child non-eating self-regulation. Bivariate correlations were run among all variables in the study. Hierarchical linear regression analyses assessed: (1) child eating self-regulation associations with the demographic, executive functioning, effortful control, and emotion regulation measures; and (2) child BMI z-score associations with executive functioning, effortful control, emotion regulation measures, and eating self-regulation measures. Within child eating self-regulation, only the two parent-report measures were related. Low to moderate positive correlations were found between measures of executive functioning, effortful control, and emotion regulation. Only three relationships were found between child eating self-regulation and other forms of child self-regulation: eating in the absence of hunger was positively associated with delay of gratification, and poor regulation on the gift delay task was associated positively with maternal reports of food responsiveness and negatively with parent-reports of satiety responsiveness. Regression analyses showed that child eating self-regulation was associated with child BMIz but other forms of child self-regulation were not. Implications for understanding the role of self-regulation in the development of child obesity are discussed.

Sleep and food intake: A multisystem review of mechanisms in children and adults

The foods we eat have substantial impact on our health, and excessive food intake is associated with numerous long-term health conditions. It is therefore essential to understand the factors influencing this crucial health behavior. Research has identified sleep problems as one such factor; however, little research has examined how sleep problems impact food intake. Using a multisystemic perspective, this article proposes a variety of ways in which sleep problems likely increase food intake and illustrates the need for research to empirically examine these underlying mechanisms. Such research would have important treatment implications for health conditions often treated with dietary interventions.

Adolescent development of inhibition as a function of SES and gender: Converging evidence from behavior and fMRI

The ability to adaptively inhibit responses to tempting/distracting stimuli in the pursuit of goals is an essential set of skills necessary for adult competence and wellbeing. These inhibitory capacities develop throughout childhood, with growing evidence of important maturational changes occurring in adolescence. There also has been intense interest in the role of social adversity on the development of executive function, including inhibitory control. We hypothesized that the onset of adolescence could be a time of particular opportunity/vulnerability in the development of inhibition due to the large degree of maturational changes in neural systems involved in regulatory control. We investigated this hypothesis in a longitudinal study of adolescents by examining the impact of socioeconomic status (SES) on the maturation of inhibition and concurrent brain function. Furthermore, we examined gender as a potential moderator of this relationship, given evidence of gender-specificity in the developmental pathways of inhibition as well as sex differences in adolescent development. Results reveal that lower SES is associated with worse behavioral inhibition over time and a concurrent increase in anterior cingulate (ACC) activation, but only in girls. We also found that lower SES girls exhibited decreased ACC ↔ dorsolateral prefrontal cortex (dlPFC) coupling over time. Our findings suggest that female adolescents with lower SES appear to develop less efficient inhibitory processing in dlPFC, requiring greater and relatively unsuccessful compensatory recruitment of ACC. In summary, the present study provides a novel window into the neural mechanisms by which the influence of SES on inhibition may be transmitted during adolescence.

Spontaneous regional brain activity links restrained eating to later weight gain among young women

Theory and prospective studies have linked restrained eating (RE) to risk for future weight gain and the onset of obesity, but little is known about resting state neural activity that may underlie this association. To address this gap, resting fMRI was used to test the extent to which spontaneous neural activity in regions associated with inhibitory control and food reward account for potential relations between baseline RE levels and changes in body weight among dieters over a one-year interval. Spontaneous regional activity patterns corresponding to RE were assessed among 50 young women using regional homogeneity (ReHo) analysis, which measured temporal synchronization of spontaneous fluctuations within a food deprivation condition. Analyses indicated higher baseline RE scores predicted more weight gain at a one-year follow-up. Furthermore, food-deprived dieting women with high dietary restraint scores exhibited more spontaneous local activity in brain regions associated with the expectation and valuation for food reward [i.e., orbitofrontal cortex (OFC)/ventromedial prefrontal cortex (VMPFC)] and reduced spontaneous local activity in inhibitory control regions [i.e., bilateral dorsal-lateral prefrontal cortex (DLPFC)] at baseline. Notably, the association between baseline RE and follow-up weight gain was mediated by decreased local synchronization of the right DLPFC in particular and, to a lesser degree, increased local synchronization of the right VMPFC. In conjunction with previous research, these findings highlight possible neural mechanisms underlying the relation between RE and risk for weight gain.

Maternal adiposity negatively influences infant brain white matter development

OBJECTIVE

To study potential effects of maternal body composition on central nervous system (CNS) development of newborn infants.

METHODS

Diffusion tensor imaging (DTI) was used to evaluate brain white matter development in 2-week-old, full-term, appropriate for gestational age (AGA) infants from uncomplicated pregnancies of normal-weight (BMI < 25 at conception) or obese ( BMI = 30 at conception) and otherwise healthy mothers. Tract-based spatial statistics (TBSS) analyses were used for voxel-wise group comparison of fractional anisotropy (FA), a sensitive measure of white matter integrity. DNA methylation analyses of umbilical cord tissue focused on genes known to be important in CNS development were also performed.

RESULTS

Newborns from obese women had significantly lower FA values in multiple white matter regions than those born of normal-weight mothers. Global and regional FA values negatively correlated (P < 0.05) with maternal fat mass percentage. Linear regression analysis followed by gene ontology enrichment showed that methylation status of 68 CpG sites representing 57 genes with GO terms related to CNS development was significantly associated with maternal adiposity status.

CONCLUSIONS

These results suggest a negative association between maternal adiposity and white matter development in offspring.

Attentional biases for food cues in overweight and individuals with obesity: a systematic review of the literature

Obesity rates have increased dramatically in recent decades, and it has proven difficult to treat. An attentional bias towards food cues may be implicated in the aetiology of obesity and influence cravings and food consumption. This review systematically investigated whether attentional biases to food cues exist in overweight/obese compared with healthy weight individuals. Electronic database were searched for relevant papers from inception to October 2014. Only studies reporting food-related attentional bias between either overweight (body mass index [BMI] 25.0-29.9 kg m(-2)) or obese (BMI ≥ 30) participants and healthy weight participants (BMI 18.5-24.9) were included. The findings of 19 studies were reported in this review. Results of the literature are suggestive of differences in attentional bias, with all but four studies supporting the notion of enhanced reactivity to food stimuli in overweight individuals and individuals with obesity. This support for attentional bias was observed primarily in studies that employed psychophysiological techniques (i.e. electroencephalogram, eye-tracking and functional magnetic resonance imaging). Despite the heterogeneous methodology within the featured studies, all measures of attentional bias demonstrated altered cue-reactivity in individuals with obesity. Considering the theorized implications of attentional biases on obesity pathology, researchers are encouraged to replicate flagship studies to strengthen these inferences.

External eating mediates the relationship between impulsivity and unhealthy food intake

Recent evidence from the eating domain shows a link between impulsivity and unhealthy food intake. However, the mechanism underlying this relationship remains unclear. One possibility is an external eating style, which has been linked to both impulsivity and food intake. The current study investigated the potential mediating role of external eating in the relationship between impulsivity and food intake. Participants were 146 undergraduate women who completed measures of impulsivity and external eating, and took part in a laboratory taste test as a behavioural index of unhealthy snack food intake. It was found that attentional and motor impulsivity interacted in predicting sweet food intake, but only motor impulsivity predicted both external eating and sweet food intake. Furthermore, the relationship between motor impulsivity and food intake was mediated by external eating. These findings support the development of interventions aimed at targeting specific aspects of impulsivity in order to reduce unhealthy eating behaviour.

Nutrition labels influence value computation of food products in the ventromedial prefrontal cortex

OBJECTIVE

Prevalence of obesity is high in most industrialized nations, and therefore, it is crucial to understand contextual factors underlying food choice. Nutrition labels are public policy interventions designed to adequately inform consumers about nutritional value and overall healthiness of food products. The present study examines how different nutrition labels, namely a purely information-based label (guideline daily amount, GDA) and a more explicit traffic light (TL) label, influence product valuation and choice in a functional MRI setting.

METHODS

Thirty-five healthy participants across different BMIs were instructed to valuate healthy and unhealthy food products in combination with one of the two labels and to state their willingness to pay (WTP) for the product.

RESULTS

The labeling methods significantly influenced participants' WTP. Red TL signaling activated parts of the left inferior frontal gyrus/dorsolateral prefrontal cortex, a region implicated in self-control in food choice. This region, in the case of red signaling, and the posterior cingulate cortex, in the case of green signaling, showed increased coupling to the valuation system in the ventromedial prefrontal cortex.

CONCLUSIONS

Our results suggest that explicitly directing attention toward nutritional values using salient nutrition labels triggers neurobiological processes that resemble those utilized by successful dieters choosing healthier products.

Prospect theory and body mass: characterizing psychological parameters for weight-related risk attitudes and weight-gain aversion

We developed a novel decision-making paradigm that allows us to apply prospect theory in behavioral economics to body mass. 67 healthy young adults completed self-report measures and two decision-making tasks for weight-loss, as well as for monetary rewards. We estimated risk-related preference and loss aversion parameters for each individual, separately for weight-loss and monetary rewards choice data. Risk-seeking tendency for weight-loss was positively correlated with body mass index in individuals who desired to lose body weight, whereas the risk-seeking for momentary rewards was not. Risk-seeking for weight-loss was correlated to excessive body shape preoccupations, while aversion to weight-gain was correlated with self-reports of behavioral involvement for successful weight-loss. We demonstrated that prospect theory can be useful in explaining the decision-making process related to body mass. Applying prospect theory is expected to advance our understanding of decision-making mechanisms in obesity, which might prove helpful for improving healthy choices.

Neuroimaging and neuromodulation approaches to study eating behavior and prevent and treat eating disorders and obesity

Functional, molecular and genetic neuroimaging has highlighted the existence of brain anomalies and neural vulnerability factors related to obesity and eating disorders such as binge eating or anorexia nervosa. In particular, decreased basal metabolism in the prefrontal cortex and striatum as well as dopaminergic alterations have been described in obese subjects, in parallel with increased activation of reward brain areas in response to palatable food cues. Elevated reward region responsivity may trigger food craving and predict future weight gain. This opens the way to prevention studies using functional and molecular neuroimaging to perform early diagnostics and to phenotype subjects at risk by exploring different neurobehavioral dimensions of the food choices and motivation processes. In the first part of this review, advantages and limitations of neuroimaging techniques, such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), single photon emission computed tomography (SPECT), pharmacogenetic fMRI and functional near-infrared spectroscopy (fNIRS) will be discussed in the context of recent work dealing with eating behavior, with a particular focus on obesity. In the second part of the review, non-invasive strategies to modulate food-related brain processes and functions will be presented. At the leading edge of non-invasive brain-based technologies is real-time fMRI (rtfMRI) neurofeedback, which is a powerful tool to better understand the complexity of human brain-behavior relationships. rtfMRI, alone or when combined with other techniques and tools such as EEG and cognitive therapy, could be used to alter neural plasticity and learned behavior to optimize and/or restore healthy cognition and eating behavior. Other promising non-invasive neuromodulation approaches being explored are repetitive transcranial magnetic stimulation (rTMS) and transcranial direct-current stimulation (tDCS). Converging evidence points at the value of these non-invasive neuromodulation strategies to study basic mechanisms underlying eating behavior and to treat its disorders. Both of these approaches will be compared in light of recent work in this field, while addressing technical and practical questions. The third part of this review will be dedicated to invasive neuromodulation strategies, such as vagus nerve stimulation (VNS) and deep brain stimulation (DBS). In combination with neuroimaging approaches, these techniques are promising experimental tools to unravel the intricate relationships between homeostatic and hedonic brain circuits. Their potential as additional therapeutic tools to combat pharmacorefractory morbid obesity or acute eating disorders will be discussed, in terms of technical challenges, applicability and ethics. In a general discussion, we will put the brain at the core of fundamental research, prevention and therapy in the context of obesity and eating disorders. First, we will discuss the possibility to identify new biological markers of brain functions. Second, we will highlight the potential of neuroimaging and neuromodulation in individualized medicine. Third, we will introduce the ethical questions that are concomitant to the emergence of new neuromodulation therapies.

Patients lacking sustainable long-term weight loss after gastric bypass surgery show signs of decreased inhibitory control of prepotent responses

Background

A considerable number of bariatric patients report poor long-term weight loss after Roux-en-Y gastric bypass (RYGB) surgery. One possibility for an underlying cause is an impairment of cognitive control that impedes this patient group’s dietary efforts.

Objective

To investigate if patients having either poor or good weight loss response, ~12 years after RYGB-surgery, differ in their ability to inhibit prepotent responses when processing food cues during attentional operations—as measure of cognitive control.

Methods

In terms of weight loss following RYGB-surgery, 15 ‘poor responders’ and 15 ‘good responders’, matched for gender, age, education, preoperative body mass index, and years since surgery, were administered two tasks that measure sustained attention and response control: a go/no-go task and a Stroop interference task; both of which are associated with maladaptive eating behaviours.

Results

The poor responders (vs. good responders) needed significantly more time when conducting a go/no-go task (603±134 vs. 519±44 msec, p = 0.03), but the number of errors did not differ between groups. When conducting a Stroop interference task, poor responders read fewer inks than good responders (68±16 vs. 85±10 words, p = 0.002).

Conclusion

Patients lacking sustainable weight loss after RYGB-surgery showed poorer inhibitory control than patients that successfully lost weight. In the authors’ view, these results suggest that cognitive behavioral therapies post-RYGB-surgery may represent a promising behavioral adjuvant to achieve sustainable weight loss in patients undergoing this procedure. Future studies should examine whether these control deficits in poor responders are food-specific or not.

Neural activation during anticipated peer evaluation and laboratory meal intake in overweight girls with and without loss of control eating

The interpersonal model of loss of control (LOC) eating proposes that socially distressing situations lead to anxious states that trigger excessive food consumption. Self-reports support these links, but the neurobiological underpinnings of these relationships remain unclear. We therefore examined brain regions associated with anxiety in relation to LOC eating and energy intake in the laboratory. Twenty-two overweight and obese (BMIz: 1.9±0.4) adolescent (15.8±1.6y) girls with LOC eating (LOC+, n=10) and without LOC eating (LOC-, n=12) underwent functional magnetic resonance imaging (fMRI) during a simulated peer interaction chatroom paradigm. Immediately after the fMRI scan, girls consumed lunch ad libitum from a 10,934-kcal laboratory buffet meal with the instruction to "let yourself go and eat as much as you want." Pre-specified hypotheses regarding activation of five regions of interest were tested. Analysis of fMRI data revealed a significant group by peer feedback interaction in the ventromedial prefrontal cortex (vmPFC), such that LOC+ had less activity following peer rejection (vs. acceptance), while LOC- had increased activity (p<.005). Moreover, functional coupling between vmPFC and striatum for peer rejection (vs. acceptance) interacted with LOC status: coupling was positive for LOC+, but negative in LOC- (p<.005). Activity of fusiform face area (FFA) during negative peer feedback from high-value peers also interacted with LOC status (p<.005). A positive association between FFA activation and intake during the meal was observed among only those with LOC eating. In conclusion, overweight and obese girls with LOC eating may be distinguished by a failure to engage regions of prefrontal cortex implicated in emotion regulation in response to social distress. The relationship between FFA activation and food intake supports the notion that heightened sensitivity to incoming interpersonal cues and perturbations in socio-emotional neural circuits may lead to overeating in order to cope with negative affect elicited by social discomfort in susceptible youth.

Metabolic vs. hedonic obesity: a conceptual distinction and its clinical implications

Body weight is determined via both metabolic and hedonic mechanisms. Metabolic regulation of body weight centres around the 'body weight set point', which is programmed by energy balance circuitry in the hypothalamus and other specific brain regions. The metabolic body weight set point has a genetic basis, but exposure to an obesogenic environment may elicit allostatic responses and upward drift of the set point, leading to a higher maintained body weight. However, an elevated steady-state body weight may also be achieved without an alteration of the metabolic set point, via sustained hedonic over-eating, which is governed by the reward system of the brain and can override homeostatic metabolic signals. While hedonic signals are potent influences in determining food intake, metabolic regulation involves the active control of both food intake and energy expenditure. When overweight is due to elevation of the metabolic set point ('metabolic obesity'), energy expenditure theoretically falls onto the standard energy-mass regression line. In contrast, when a steady-state weight is above the metabolic set point due to hedonic over-eating ('hedonic obesity'), a persistent compensatory increase in energy expenditure per unit metabolic mass may be demonstrable. Recognition of the two types of obesity may lead to more effective treatment and prevention of obesity.

Enhanced neural responsiveness to reward associated with obesity in the absence of food-related stimuli

BACKGROUND

Obesity has been characterized by alterations in brain structure and function associated with emotion processing and regulation. Particularly, aberrations in food-related reward processing have been frequently demonstrated in obese subjects. However, it remains unclear whether reward-associated functional aberrations in obesity are specific for food-related stimuli or represent a general deficit in reward processing, extending to other stimulus domains. Given the crucial role of rewarding effects in the development of obesity and the ongoing discussion on overlapping neurobiological traits of obesity and psychiatric disorders such as depression and substance-related disorders, this study aimed to investigate the possibility of altered reward processing in obese subjects to occur in the absence of food-related stimuli during a monetary reward condition.

METHODS

Twenty-nine healthy obese subjects (body mass index >30) and 29 healthy, age-, and sex-matched control subjects of normal weight underwent functional MRI during a frequently used card guessing paradigm. A Group × Condition (win vs. loss) ANOVA was conducted to investigate differences between obese and normal-weight subjects.

RESULTS

We found significant Group × Condition interaction effects in brain areas involved in emotion regulation and reward processing including the insula, the striatum, and the orbitofrontal cortex (OFC). This interaction was predominantly driven by a significant increase in blood oxygenation level dependent (BOLD) response in obese individuals while experiencing reward.

CONCLUSIONS

Enhanced neural activation in obesity during reward processing seems to be apparent even in the absence of food-related stimuli and, thus, might point to generalized dysfunctions in reward-related brain circuits in obese individuals.

Neural circuits for cognitive appetite control in healthy and obese individuals: an fMRI study

The mere sight of foods may activate the brain’s reward circuitry, and humans often experience difficulties in inhibiting urges to eat upon encountering visual food signals. Imbalance between the reward circuit and those supporting inhibitory control may underlie obesity, yet brain circuits supporting volitional control of appetite and their possible dysfunction that can lead to obesity remain poorly specified. Here we delineated the brain basis of volitional appetite control in healthy and obese individuals with functional magnetic resonance imaging (fMRI). Twenty-seven morbidly obese women (mean BMI = 41.4) and fourteen age-matched normal-weight women (mean BMI = 22.6) were scanned with 1.5 Tesla fMRI while viewing food pictures. They were instructed to inhibit their urge to eat the foods, view the stimuli passively or imagine eating the foods. Across all subjects, a frontal cortical control circuit was activated during appetite inhibition versus passive viewing of the foods. Inhibition minus imagined eating (appetite control) activated bilateral precunei and parietal cortices and frontal regions spanning anterior cingulate and superior medial frontal cortices. During appetite control, obese subjects had lower responses in the medial frontal, middle cingulate and dorsal caudate nuclei. Functional connectivity of the control circuit was increased in morbidly obese versus control subjects during appetite control, which might reflect impaired integrative and executive function in obesity.

The independent and interacting effects of hedonic hunger and executive function on binge eating

Poor executive function (EF; pre-frontal cognitive control processes governing goal-directed behavior) and elevated hedonic hunger (i.e., preoccupation with palatable foods in the absence of physiological hunger) are theoretical risk and maintenance factors for binge eating (BE) distinct from general obesity. Recent theoretical models posit that dysregulated behavior such as BE may result from a combination of elevated appetitive drive (e.g., hedonic hunger) and decreased EF (e.g., inhibitory control and delayed discounting). The present study sought to test this model in distinguishing BE from general obesity by examining the independent and interactive associations of EF and hedonic hunger with BE group status (i.e., odds of categorization in BE group versus non-BE group). Treatment-seeking overweight and obese women with BE (n = 31) and without BE (OW group; n = 43) were assessed on measures of hedonic hunger and EF (inhibitory control and delay discounting). Elevated hedonic hunger increased the likelihood of categorization in the BE group, regardless of EF. When hedonic hunger was low, poor EF increased the likelihood of categorization in the BE group. Results indicate that the interplay of increased appetitive drives and decreased cognitive function may distinguish BE from overweight/obesity. Future longitudinal investigations of the combinatory effect of hedonic hunger and EF in increasing risk for developing BE are warranted, and may inform future treatment development to target these factors.

Obesity and major depression: Body-mass index (BMI) is associated with a severe course of disease and specific neurostructural alterations

Obesity is one of the most prevalent somatic comorbidities of major depressive disorder (MDD). Both disorders rank among the leading challenges in public health and have been independently characterized by gray matter alterations in partly overlapping brain structures. Hence, it appears crucial to investigate the possibility of a shared neurostructural correlate of this frequent comorbidity as well as its clinical implications. One hundred and fourty-four patients suffering from acute MDD and 141 healthy control subjects underwent structural MRI. Imaging data were analyzed using voxel-based morphometry (VBM). Body-mass-index (BMI) as well as state and course of disease were assessed. Higher BMI was associated with a highly comparable pattern of gray matter reductions in the medial prefrontal cortex, the orbitofrontal cortex, the caudate nucleus and the thalamus in MDD patients and healthy controls alike. In MDD-patients, BMI was associated with a more chronic course of disease and both BMI and chronicity of disorder were related to similar morphometric anomalies in medial prefrontal areas. In MDD, obese subjects might be characterized by a more chronic course of disease. Moreover, obesity and chronicity of disorder seem to share overlapping neurostructural anomalies in prefrontal areas involved in emotion regulation and impulse control. Hence, our data provide evidence for specific morphological alterations underlying this prevalent comorbidity. It further underlines the clinical importance of preventive measures against obesity accompanying MDD treatment.

Gray and white matter structures in the midcingulate cortex region contribute to body mass index in Chinese young adults

Overweight and obesity are rapidly becoming a central public health challenge around the world. Previous studies have suggested that elevated Body Mass Index (BMI) might be associated with structural changes in both gray and white matter, but this association is still not well understood. The present study aimed to investigate the relationship between BMI and brain structure with a relatively large sample of young adults (N = 336) in a small age range (20 ± 1 years). Voxel-based morphometry results showed significant negative correlations between BMI and gray-matter volumes in the midcingulate cortex (MCC), left orbital frontal cortex, and left ventromedial prefrontal cortex. There was also a significant negative correlation between BMI and white matter integrity as indexed by fractional anisotropy in bilateral cingulum. Further tractography analysis showed a significant negative correlation between BMI and the number of fibers passing the MCC region. Regression analysis showed that gray matter and white matter in these regions both contributed to the variance of BMI. These results remained significant even when analysis was restricted to the subjects with normal weights. Finally, we found that decision-making ability (as assessed by the Iowa Gambling Task) mediated the association between the structure of the MCC (a region responsible for impulse control and decision making) and BMI. These results shed light on the structural neural basis of weight variations.

Cognitive function and nonfood-related impulsivity in post-bariatric surgery patients

Initial evidence that cognitive function improves after bariatric surgery exists. The post-surgery increase in cognitive control might correspond with a decrease of impulsive symptoms after surgery. The present study investigated cognitive function and nonfood-related impulsivity in patients with substantial weight loss due to bariatric surgery by using a comparative cross-sectional design. Fifty post-bariatric surgery patients (postBS group) who had significant percent weight loss (M = 75.94, SD = 18.09) after Roux-en-Y gastric bypass (body mass index, BMI M_post = 30.54 kg/m², SD_post = 5.14) were compared with 50 age and gender matched bariatric surgery candidates (preBS group; BMI M_pre = 48.01 kg/m², SD_pre = 6.56). To measure cognitive function the following computer-assisted behavioral tasks were utilized: Iowa Gambling Task, Tower of Hanoi, Stroop Test, Trail Making Test-Part B, and Corsi Block Tapping Test. Impulsive symptoms and behaviors were assessed using impulsivity questionnaires and a structured interview for impulse control disorders (ICDs). No group differences were found with regard to performance-based cognitive control, self-reported impulsive symptoms, and ICDs. The results indicate that the general tendency to react impulsively does not differ between pre-surgery and post-surgery patients. The question of whether nonfood-related impulsivity in morbidly obese patients changes post-surgery should be addressed in longitudinal studies given that impulsive symptoms can be considered potential targets for pre- as well post-surgery interventions.

Neural predictors of chocolate intake following chocolate exposure

Previous studies have shown that one's brain response to high-calorie food cues can predict long-term weight gain or weight loss. The neural correlates that predict food intake in the short term have, however, hardly been investigated. This study examined which brain regions' activation predicts chocolate intake after participants had been either exposed to real chocolate or to control stimuli during approximately one hour, with interruptions for fMRI measurements. Further we investigated whether the variance in chocolate intake could be better explained by activated brain regions than by self-reported craving. In total, five brain regions correlated with subsequent chocolate intake. The activation of two reward regions (the right caudate and the left frontopolar cortex) correlated positively with intake in the exposure group. The activation of two regions associated with cognitive control (the left dorsolateral and left mid-dorsolateral PFC) correlated negatively with intake in the control group. When the regression analysis was conducted with the exposure and the control group together, an additional region's activation (the right anterior PFC) correlated positively with chocolate intake. In all analyses, the intake variance explained by neural correlates was above and beyond the variance explained by self-reported craving. These results are in line with neuroimaging research showing that brain responses are a better predictor of subsequent intake than self-reported craving. Therefore, our findings might provide for a missing link by associating brain activation, previously shown to predict weight change, with short-term intake.

Stopping to food can reduce intake. Effects of stimulus-specificity and individual differences in dietary restraint

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We examine whether cognitive training (response inhibition) modifies food intake.

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Food stimulus-specific training can influence food intake.

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These effects are more pronounced in restrained eaters.

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General training to non-food stimuli did not influence food intake.

Overeating in our food-rich environment is a key contributor to obesity. Computerised response-inhibition training could improve self-control in individuals who overeat. Evidence suggests that training people to inhibit motor responses to specific food pictures can reduce the subsequent choice and consumption of those foods. Here we undertook three experiments using the stop-signal task to examine the effects of food and non-food related stop-training on immediate snack food consumption. The experiments examined whether training effects were stimulus-specific, whether they were influenced by the comparator (control) group, and whether they were moderated by individual differences in dietary restraint. Experiment 1 revealed lower intake of one food following stop- vs. double- (two key-presses) response training to food pictures. Experiment 2 offered two foods, one of which was not associated with stopping, to enable within- and between-subjects comparisons of intake. A second control condition required participants to ignore signals and respond with one key-press to all pictures. There was no overall effect of training on intake in Experiment 2, but there was a marginally significant moderation by dietary restraint: Restrained eaters ate significantly less signal-food following stop- relative to double-response training. Experiment 3 revealed that stop- vs. double-response training to non-food pictures had no effect on food intake. Taken together with previous findings, these results suggest some stimulus-specific effects of stop-training on food intake that may be moderated by individual differences in dietary restraint.

Altered dynamics between neural systems sub-serving decisions for unhealthy food

Using BOLD functional magnetic resonance imaging (fMRI) techniques, we examined the relationships between activities in the neural systems elicited by the decision stage of the Iowa Gambling Task (IGT), and food choices of either vegetables or snacks high in fat and sugar. Twenty-three healthy normal weight adolescents and young adults, ranging in age from 14 to 21, were studied. Neural systems implicated in decision-making and inhibitory control were engaged by having participants perform the IGT during fMRI scanning. The Youth/Adolescent Questionnaire, a food frequency questionnaire, was used to obtain daily food choices. Higher consumption of vegetables correlated with higher activity in prefrontal cortical regions, namely the left superior frontal gyrus (SFG), and lower activity in sub-cortical regions, namely the right insular cortex. In contrast, higher consumption of fatty and sugary snacks correlated with lower activity in the prefrontal regions, combined with higher activity in the sub-cortical, insular cortex. These results provide preliminary support for our hypotheses that unhealthy food choices in real life are reflected by neuronal changes in key neural systems involved in habits, decision-making and self-control processes. These findings have implications for the creation of decision-making based intervention strategies that promote healthier eating.