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

Neural processing of food cues in pre-pubertal children

BACKGROUND/OBJECTIVES

Neuroimaging investigations of brain pathways involved in reward and motivation have primarily focused on adults. This study sought to identify brain responses to visual food cues and explore its relationships with adiposity and sex in pre-pubertal children.

METHODS

Brain responses to palatable food vs. non-food cues were measured in 53 children (age: 8.18 ± .66 years; sex: 22 boys, 31 girls) after an overnight fast. Whole-brain analysis (cluster-correction Z > 2.3, P < .05) was performed to examine brain food cue reactivity and its relationships with adiposity and sex.

RESULTS

Greater brain activity in response to food vs. non-food cues was observed in regions implicated in reward (orbital frontal cortex, striatum), taste (insula, postcentral gyrus), appetite (hypothalamus), emotion (amygdala), memory (hippocampus), visual processing (occipital cortex) and attention (parietal cortex). A negative association was found between percent body fat and food cue reactivity in the medial prefrontal cortex and lateral orbital frontal cortex adjusting for age and sex. Boys compared with girls had increased food cue reactivity in right hippocampus and visual cortex.

CONCLUSIONS

These data suggest that body fat and sex are important moderators of brain food cue reactivity in children.

Food or money? Children's brains respond differently to rewards regardless of weight status

BACKGROUND

Brain responses to both food and monetary rewards have been linked to weight gain and obesity in adults, suggesting that general sensitivity to reward contributes to overeating. However, the relationship between brain reward response and body weight in children is unclear.

OBJECTIVE

The objective of this study was to assess the brain's response to multiple rewards and the relationship to body weight in children.

METHODS

We tested this by performing functional magnetic resonance imaging while children (7- to 11-years-old; healthy weight [n = 31], overweight/obese [n = 30]) played a modified card-guessing task to assess blood-oxygen-level-dependent (BOLD) response to anticipating and winning food and money rewards. Functional magnetic resonance imaging data were analysed using a region of interest and exploratory whole-brain approach.

RESULTS

Region of interest results demonstrated increased BOLD response in the striatum to anticipating food vs. neutral (control) and winning money vs. neutral. Whole-brain data showed that winning money vs. food was associated with increased activation in the striatum, as well as regions associated with cognitive control and emotion. Notably, for both approaches, these effects were independent of child weight status. Additionally, children's reported food responsiveness and emotional overeating were negatively correlated with the BOLD response in the left cingulate gyrus for winning food vs. money.

CONCLUSION

Overall, findings from this study show that regions associated with reward, cognitive control and emotion may play a role in the brain's response to food and money rewards, independently of how much the child weighs. These findings provide insight into reward sensitivity in children, which may have implications for understanding overeating and the development of obesity.

Neurocognitive and Hormonal Correlates of Voluntary Weight Loss in Humans

Insufficient responses to hypocaloric diets have been attributed to hormonal adaptations that override self-control of food intake. We tested this hypothesis by measuring circulating energy-balance hormones and brain functional magnetic resonance imaging reactivity to food cues in 24 overweight/obese participants before, and 1 and 3 months after starting a calorie restriction diet. Increased activity and functional connectivity in prefrontal regions at month 1 correlated with weight loss at months 1 and 3. Weight loss was also correlated with increased plasma ghrelin and decreased leptin, and these changes were associated with food cue reactivity in reward-related brain regions. However, the reduction in leptin did not counteract weight loss; indeed, it was correlated with further weight loss at month 3. Activation in prefrontal regions associated with self-control could contribute to successful weight loss and maintenance. This work supports the role of higher-level cognitive brain function in body-weight regulation in humans.

Prefrontal brain stimulation during food-related inhibition training: effects on food craving, food consumption and inhibitory control

Modulation of dorsolateral prefrontal cortex (DLPFC) activity using non-invasive brain stimulation has been shown to reduce food craving as well as food consumption. Using a preregistered design, we examined whether bilateral transcranial direct current stimulation (tDCS) of the DLPFC could reduce food craving and consumption in healthy participants when administered alongside the cognitive target of inhibitory control training. Participants (N = 172) received either active or sham tDCS (2 mA; anode F4, cathode F3) while completing a food-related Go/No-Go task. State food craving, ad-lib food consumption and response inhibition were evaluated. Compared with sham stimulation, we found no evidence for an effect of active tDCS on any of these outcome measures in a predominantly female sample. Our findings raise doubts about the effectiveness of single-session tDCS on food craving and consumption. Consideration of individual differences, improvements in tDCS protocols and multi-session testing are discussed.

Neurocognitive decision-making processes of casual methamphetamine users

Neuroadaptations caused by chronic methamphetamine (MA) use are likely major contributors to high relapse rate following treatment. Thus, focusing intervention efforts at pre-empting addiction in vulnerable populations, thereby preventing MA-use-induced neurological changes that make recovery so challenging, may prove more effective than targeting chronic users. One approach is studying casual/recreational users, not diagnosed with substance use disorder. This group may be at high risk for addiction due to their experience with MA. On the other hand, they may be resilient against addiction since they were able to maintain casual use over the years and not become addicted. Understanding their neuro-cognitive characteristics during decision-making and risk-taking would help solve this dilemma and, may help identify intervention strategies. Unfortunately, research on neuro-cognitive characteristics of casual MA users is currently lacking. In this work we begin to address this deficit.

This study was part of a larger investigation of neural correlates of risky sexual decision-making in men who have sex with men. While undergoing functional magnetic resonance imaging, 31 casual MA users and 66 non-users performed the CUPS task, in which they decided to accept or refuse a series of mixed gambles. Convergent results from whole brain, region of interest and psychophysiological interaction (PPI) analyses are presented.

Whole brain analysis identified an amygdala-striatal cluster with weaker activation in casual MA users compared to non-users during decision-making. Activity in that cluster inversely correlated with decisions to gamble: lower activation corresponded to higher risk taking. Using this cluster as a seed in PPI analyses, we identified a wide range of neural network differences between casual MA users and non-users. Parametric whole brain analyses identified clusters in the ventral striatum, posterior insula and precuneus where activations modulated by risk and reward were significantly weaker in casual MA users than in non-users. The striatal cluster identified in these analyses overlapped with the amygdala-striatal cluster.

This work identified neural differences in casual MA users' reward processing and outcome learning systems which may underlie their increased real-world risk-taking. It suggests that while making decisions casual MA users focus primarily on potential gain unlike non-users who also take the riskiness of the choice into consideration.

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Neurocognitive processes of casual meth users, not yet addicted but at high risk.

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Convergent results from whole brain, psychophysiological interaction and ROI.

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Isolated key deficits in reward processing and outcome learning.

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Identified deficits may contribute to increased lab and real-world risk-taking.

Neuropsychological and Neurophysiological Indicators of General and Food-Specific Impulsivity in Children with Overweight and Obesity: A Pilot Study

Impulsivity, particularly towards food, is a potential risk factor for increased energy intake and the development and maintenance of obesity in children. However, neuropsychological and neurophysiological indicators of general and food-specific impulsivity and their association with children's weight status are poorly understood. This pilot study examined electroencephalography (EEG) frequency band profiles during eyes-closed and eyes-open resting state in n = 12 children with overweight or obesity versus n = 22 normal-weight controls and their link to child- and parent-reported and experimentally assessed impulsivity of children (e.g., risk-taking behavior, approach-avoidance behavior towards food). The main results indicated that children with overweight/obesity versus normal weight showed significantly increased delta and decreased alpha band activity during eyes-closed resting state. Across the total sample, EEG slow-wave band activity was particularly linked to self- and parent-reported impulsivity and greater risk-taking behavior, but not to approach behavior towards food, after controlling for children's age and weight status. The identification of specific EEG patterns in children with excess weight may provide a new basis for developing neurophysiological diagnostic and treatment approaches for childhood obesity. Future studies with larger samples and longitudinal designs are needed to replicate the present findings and test their stability over time.

Behavioral and Neural Evidence of the Rewarding Value of Exercise Behaviors: A Systematic Review

BACKGROUND

In a time of physical inactivity pandemic, attempts to better understand the factors underlying the regulation of exercise behavior are important. The dominant neurobiological approach to exercise behavior considers physical activity to be a reward; however, negative affective responses during exercise challenge this idea.

OBJECTIVE

Our objective was to systematically review studies testing the automatic reactions triggered by stimuli associated with different types of exercise behavior (e.g. physical activity, sedentary behaviors) and energetic cost variations (e.g. decreased energetic cost, irrespective of the level of physical activity). We also examined evidence supporting the hypothesis that behaviors minimizing energetic cost (BMEC) are rewarding.

METHODS

Two authors systematically searched, screened, extracted, and analyzed data from articles in the MEDLINE database.

RESULTS

We included 26 studies. Three outcomes of automatic processes were tested: affective reactions, attentional capture, and approach tendencies. Behavioral results show that physical activity can become attention-grabbing, automatically trigger positive affect, and elicit approach behaviors. These automatic reactions explain and predict exercise behaviors; however, the use of a wide variety of measures prevents drawing solid conclusions about the specific effects of automatic processes. Brain imaging results are scarce but show that stimuli associated with physical activity and, to a lesser extent, sedentary behaviors activate regions involved in reward processes. Studies investigating the rewarding value of behaviors driving energetic cost variations such as BMEC are lacking.

CONCLUSION

Reward is an important factor in exercise behavior. The literature based on the investigation of automatic behaviors seems in line with the suggestion that physical activity is rewarding, at least for physically active individuals. Results suggest that sedentary behaviors could also be rewarding, although this evidence remains weak due to a lack of investigations. Finally, from an evolutionary perspective, BMEC are likely to be rewarding; however, no study has investigated this hypothesis. In sum, additional studies are required to establish a strong and complete framework of the reward processes underlying automatic exercise behavior.

Food commercials do not affect energy intake in a laboratory meal but do alter brain responses to visual food cues in children

Food commercials promote snack intake and alter food decision-making, yet the influence of exposure to food commercials on subsequent neural processing of food cues and intake at a meal is unclear. This study tested whether exposing children to food or toy commercials altered subsequent brain response to high- and low-energy dense food cues and influenced laboratory intake at a multi-item, ad libitum meal. Forty-one 7-9-year-old children (25 healthy weight; 16 with overweight/obesity) completed five visits as part of a within-subjects design where they consumed multi-item test-meals under three conditions: no exposure, food commercial exposure, and toy commercial exposure. On the fourth and fifth visits, functional magnetic resonance imaging (fMRI) was performed while children viewed low- and high-energy dense food images following exposure to either food or toy commercials. Linear mixed models tested for differences in meal energy intake by commercial condition. A whole-brain analysis was conducted to compare differences in response by commercial condition and child weight status. Meal intake did not differ by commercial condition (p = 0.40). Relative to toy commercials, food commercials reduced brain response to high-energy food stimuli in cognitive control regions, including bilateral superior temporal gyri, middle temporal gyrus, and inferior frontal gyrus. Commercial condition * weight status interactions were observed in orbitofrontal cortex, fusiform gyrus, and supramarginal gyrus. Children with overweight/obesity showed increased response in these regions to high-energy stimuli following food commercials. Food commercial exposure affected children's subsequent processing of food cues by reducing engagement of the prefrontal cortex, a region implicated in cognitive control. Even though food commercial exposure did not increase intake at a meal, the effect of reduced prefrontal cortical engagement on a broader range of consumption patterns warrants investigation.

Neural correlates of the energetic value of food during visual processing and response inhibition

Previous research showed that human brain regions involved in reward and cognitive control are responsive to visually presented food stimuli, in particular high-energy foods. However, it is still to be determined whether the preference towards high-energy foods depends on their higher energy density (kcal/gram), or is based on the difference in energy content of the food items (total amount of kcal). Here we report the results of an fMRI study in which normal-weight healthy participants processed food images during a one-back task or were required to inhibit their response towards food stimuli during a Go/No-Go task. High-energy density (HD) and low-energy density (LD) foods were matched for energy content displayed. Food-related kitchen objects (OBJ) were used as control stimuli. The lateral occipital complex and the orbitofrontal cortex showed consistent higher activity in response to HD than LD foods, both during visual processing and response inhibition. This result suggests that images of HD foods, even when the amount of food shown is not associated with a higher energy content, elicit preferential visual processing - possibly involving attentional processes - and trigger a response from the reward system. We conclude that the human brain is able to distinguish food energy densities of food items during both active visual processing and response inhibition.

Unconscious response inhibition differences between table tennis athletes and non-athletes

Background

Response inhibition is associated with successful sporting performance. However, research on response inhibition in athletes from open-skill sports has mainly focused on a consciously triggered variety; little is known about open-skill athletes’ response inhibition elicited by unconscious stimuli.

Methods

Here, we explored unconscious response inhibition differences between table tennis athletes (n = 20) and non-athletes (n = 19) using the masked go/no-go task and event-related potentials technique (ERPs).

Results

At the behavioral level, table tennis athletes displayed shorter go-response times (RTs) than non-athletes in the conscious condition. Furthermore, table tennis athletes exhibited longer response time–slowing (RT-slowing) than non-athletes in the unconscious condition. At the neural level, table tennis athletes displayed shorter event-related potential N2 component latencies than non-athletes for all conditions. More importantly, athletes displayed larger no-go event-related potential P3 component amplitudes than non-athletes at both the conscious and unconscious levels.

Discussion

The present study results suggested that table tennis athletes have superior conscious and unconscious response inhibition compared to non-athletes.

Neuroimaging, neuromodulation, and population health: the neuroscience of chronic disease prevention

Preventable chronic diseases are the leading cause of death in the majority of countries throughout the world, and this trend will continue for the foreseeable future. The potential to offset the social, economic, and personal burdens associated with such conditions depends on our ability to influence people's thought processes, decisions, and behaviors, all of which can be understood with reference to the brain itself. Within the health neuroscience framework, the brain can be viewed as a predictor, mediator, moderator, or outcome in relation to health-related phenomena. This review explores examples of each of these, with specific reference to the primary prevention (i.e., prevention of initial onset) of chronic diseases. Within the topic of primary prevention, we touch on several cross-cutting themes (persuasive communications, delay discounting of rewards, and self-control), and place a special focus on obesity as a disorder influenced by both eating behavior and exercise habits.

Neural predictors of eating behavior and dietary change

Recently, there has been an increase in the number of human neuroimaging studies seeking to predict behavior above and beyond traditional measurements such as self-report. This trend has been particularly notable in the area of food consumption, as the percentage of people categorized as overweight or obese continues to rise. In this review, we argue that there is considerable utility in this form of health neuroscience, modeling the neural bases of eating behavior and dietary change in healthy community populations. Further, we propose a model and accompanying evidence indicating that several basic processes underlying eating behavior, particularly reactivity, regulation, and valuation, can be predictive of behavior change. We also discuss future directions for this work.

Overweight adolescents' brain response to sweetened beverages mirrors addiction pathways

Many adolescents struggle with overweight/obesity, which exponentially increases in the transition to adulthood. Overweight/obesity places youth at risk for serious health conditions, including type 2 diabetes. In adults, neural substrates implicated in addiction (e.g., orbitofrontal cortex (OFC), striatum, amygdala, and ventral tegmental area) have been found to be relevant to risk for overweight/obesity. In this study, we examined three hypotheses to disentangle the potential overlap between addiction and overweight/obesity processing by examining (1) brain response to high vs. low calorie beverages, (2) the strength of correspondence between biometrics, including body mass index (BMI) and insulin resistance, and brain response and (3) the relationship between a measure of food addiction and brain response using an established fMRI gustatory cue exposure task with a sample of overweight/obese youth (M age = 16.46; M BMI = 33.1). Greater BOLD response was observed across the OFC, inferior frontal gyrus (IFG), nucleus accumbens, right amygdala, and additional frontoparietal and temporal regions in neural processing of high vs. low calorie beverages. Further, BMI scores positively correlated with BOLD activation in the high calorie > low calorie contrast in the right postcentral gyrus and central operculum. Insulin resistance positively correlated with BOLD activation across the bilateral middle/superior temporal gyrus, left OFC, and superior parietal lobe. No relationships were observed between measures of food addiction and brain response. These findings support the activation of parallel addiction-related neural pathways in adolescents' high calorie processing, while also suggesting the importance of refining conceptual and neurocognitive models to fit this developmental period.

Risky decision-making after exposure to a food-choice task in excess weight adolescents: Relationships with reward-related impulsivity and hunger

OBJECTIVE

To assess the effects of exposure to a food-choice task (appetizing versus healthy food) on risky decision-making by excess versus normal weight adolescents. We also analyzed the influence of food visualization on hunger levels, as well as group differences in food choices and impulsivity.

METHODS

Fifty-six adolescents (aged 13-18 years) classified as excess (n = 27) or normal (n = 29) weight participated in the study. Risky-decision-making was assessed through the Balloon Analogue Risk Task, which was administered before and after a food-choice task. We also evaluated impulsivity traits through the UPPS-P Scale, and subjective hunger levels with a visual analogue scale.

RESULTS

Adolescents with excess weight showed enhanced risky decision-making after the food-choice task compared to normal weight adolescents, as well as increased hunger levels. Furthermore, excess weight adolescents made more appetizing choices, and showed greater scores for Positive Urgency and Sensation Seeking. Reward-related impulsivity measures were positively associated with the number of appetizing choices in the food-choice task. Several associations were found between impulsivity measures, hunger levels and risk-taking variables.

CONCLUSIONS

Excess weight adolescents increased their risky-decision-making after food exposure and this augmentation was associated with the increase in hunger levels. Increased hunger levels and risk-taking after food exposure could lead to overeating. Alterations in decision-making caused by food signals may be a long-term risk factor for the development of obesity in adulthood. In modern societies, with the high availability and continuous exposure to food cues, decision-making may be a crucial factor in maintain healthy eating habits in adolescents.

Roles of posterior parietal and dorsal premotor cortices in relative pitch processing: Comparing musical intervals to lexical tones

Humans use time-varying pitch patterns to convey information in music and speech. Recognition of musical melodies and lexical tones relies on relative pitch (RP), the ability to identify intervals between two pitches. RP processing in music is usually more fine-grained than that in tonal languages. In Western music, there are twelve pitch categories within an octave, whereas there are only three level (non-glide) lexical tones in Taiwanese (or Taiwanese Hokkien, a tonal language). The present study aimed at comparing the neural substrates underlying RP processing of musical melodic intervals with that of level lexical tones in Taiwanese. Functional magnetic resonance imaging data from fourteen participants with good RP were analyzed. The results showed that imagining the sounds of visually presented musical intervals was associated with enhanced activity in the central subregion of the right dorsal premotor cortex (dPMC), right posterior parietal cortex (PPC), and right dorsal precuneus compared to auditory imagery of visually presented Taiwanese bi-character words with level lexical tones. During the sound-congruence-judgement task (auditory imagery of musical intervals or bi-character words, and subsequently judging if the imagined sounds were melodically congruent with heard sounds), the contrast of the musical minus linguistic conditions yielded activity in the bilateral dPMC-PPC network and dorsal precuneus, with the dPMC activated in the rostral subregion. The central dPMC and PPC may mediate the attention-based maintenance of pitch intervals, whereas the dorsal precuneus may support attention control and the spatial/sensorimotor processing of the fine-grained pitch structures of music. When judging the congruence between the imagined and heard musical intervals, the bilateral rostral dPMC may play a role in attention control, working memory, evaluation of motor activities, and monitoring mechanisms. Based on the findings of this study and recent studies of amusia, we suggest that higher order cognitive operations are critical to the more fine-grained pitch processing of musical melodies compared to lexical tones.

Executive and Reward-Related Function in Pediatric Obesity: A Meta-Analysis

OBJECTIVE

This study examined the effect of pediatric obesity on executive function and reward-related decision-making, cognitive processes that are relevant to obesogenic behaviors, and evaluated their association with sample (e.g., age, gender, intelligence, and socioeconomic status, SES) and study/task (e.g., categorical/continuous variable, food stimuli) characteristics.

METHODS

A random-effects meta-analysis was conducted using Hedge's g effect sizes of published studies from 1960 to 2016, limited to children younger than the age of 21 years without medical comorbidities. Analysis included estimation of heterogeneity (τ²), publication bias (funnel-plot symmetry and fail-safe N), and sensitivity analyses for sample and study/task characteristics.

RESULTS

Across 68 studies with 70 samples, obesity was associated with worse functioning overall (-0.24; 95CI: -0.30 to -0.19; p < 0.001) and for each component process (attention, switching, inhibition, interference, working memory, reward, delay of gratification: -0.19 to -0.38; p's < 0.017), except trait impulsivity (-0.06; 95CI: -0.18 to 0.07). Deficits increased with age and female composition of the sample for inhibition (p = 0.002). No other characteristics moderated effect of obesity.

CONCLUSIONS

Small-to-moderate negative associations with obesity were observed for executive and reward-related performance, but not on reported impulsivity in studies with children younger than the age of 21 years. These results were not moderated by IQ, SES, and study/task characteristics. Age and gender moderated association with inhibition, with a larger obesity-related deficit in older and predominantly female samples. These results suggest cognitive and demographic intervention targets for prevention and mitigation of obesogenic behavior.

Is brain response to food rewards related to overeating? A test of the reward surfeit model of overeating in children

The reward surfeit model of overeating suggests that heightened brain response to rewards contributes to overeating and subsequent weight gain. However, previous studies have not tested whether brain response to reward is associated with food intake, particularly during childhood, a period of dynamic development in reward and inhibitory control neurocircuitry. We conducted functional magnetic resonance imaging (fMRI) with 7-11-year-old children (n = 59; healthy weight, n = 31; overweight, n = 28; 54% female) while they played a modified card-guessing paradigm to examine blood-oxygen-level-dependent (BOLD) response to anticipating and winning rewards (food, money, neutral). Food intake was assessed at three separate meals that measured different facets of eating behavior: 1) typical consumption (baseline), 2) overindulgence (palatable buffet), and 3) eating in the absence of hunger (EAH). A priori regions of interest included regions implicated in both reward processing and inhibitory control. Multiple stepwise regressions were conducted to examine the relationship between intake and BOLD response to rewards. Corrected results showed that a greater BOLD response in the medial prefrontal cortex for anticipating food compared to money positively correlated with how much children ate at the baseline and palatable buffet meals. BOLD response in the dorsolateral prefrontal cortex for winning food compared to money was positively correlated with intake at the palatable buffet meal and EAH. All aforementioned relationships were independent of child weight status. Findings support the reward surfeit model by showing that increased brain response to food compared to money rewards positively correlates with laboratory measures of food intake in children.

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

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

Elevated body-mass index is associated with reduced white matter integrity in two large independent cohorts

Obesity has been associated with a variety of neurobiological alterations. Recent neuroimaging research has pointed to the relevance of brain structural and functional alterations in the development of obesity. However, while the role of gray matter atrophy in obesity has been evidenced in several well powered studies, large scale evidence for altered white matter integrity in obese subjects is still absent. With this study, we therefore aimed to investigate potential associations between white matter abnormalities and body mass index (BMI) in two large independent samples of healthy adults. Associations between BMI values and whole brain fractional anisotropy (FA) were investigated in two independent cohorts: A sample of n = 369 healthy subjects from the Münster Neuroimaging Cohort (MNC), as well as a public available sample of n = 1064 healthy subjects of the Humane Connectome Project (HCP) were included in the present study. Tract based spatial statistics (TBSS) analyses of BMI on whole brain FA were conducted including age and sex as nuisance covariates using the FMRIB library (FSL Version 5.0). Threshold-free cluster enhancement was applied to control for multiple comparisons. In both samples higher BMI was significantly associated with strong and widespread FA reductions. These effects were most pronounced in the corpus callosum, bilateral posterior thalamic radiation, bilateral internal capsule and external capsule, bilateral inferior longitudinal fasciculus and inferior fronto-occipital fasciculus. The association was found to be independent of age, sex and other cardiovascular risk factors. No significant positive associations between BMI and FA occurred. With this highly powered study, we provide robust evidence for globally reduced white matter integrity associated with elevated BMI including replication in an independent sample. The present work thus points out the relevance of white matter alterations as a neurobiological correlate of obesity.

Sleep Health and Psychopathology Mediate Executive Deficits in Pediatric Obesity

OBJECTIVE

Executive and motivational dysfunction have been associated with pediatric obesity. Poor sleep quality and psychopathology, often comorbid with obesity, are also associated with executive and motivational dysfunction. We examined the contribution of these comorbid factors to the association between obesity and executive function and reward-related decision-making.

METHODS

Seven- to 18-year-old children with and without obesity performed a working memory task with low and high loads, a response inhibition task, and a probabilistic reward-related decision-making task. Parents filled out standardized measures of executive function in everyday behavior, sleep health, and psychiatric symptoms. Analyses controlled for age, gender, IQ, and parental education.

RESULTS

Children with obesity showed worse working memory performance under higher load (p = 0.007), and worse parent-reported behavioral regulation (p = 0.05) and metacognition (p = 0.04) in everyday behavior and their reward-related decision-making was less consistent with learned probabilistic conditions (p = 0.04). Response inhibition did not differ between groups. Children with obesity had worse parent-reported sleep health (p < 0.01) and 4.27 greater odds of clinically relevant internalizing symptomology (p = 0.03), both of which mediated the effect of obesity on behavioral regulation (p's < 0.01) and metacognition (p's < 0.01). Performance-based assessments were not associated with sleep health or psychopathology.

CONCLUSIONS

Sleep quality and internalizing psychopathology were worse in children with obesity and contributed to parent-reported executive dysfunction in their everyday behavior. Performance-based measures of working memory and decision-making were not associated with those comorbidities of obesity.

The role of emotion regulation in childhood obesity: implications for prevention and treatment

Stress and negative emotions pose a major threat to public health, by increasing the risk of obesity. Since the management process for emotions (emotion regulation; ER) is developed in childhood, we present a novel conceptual framework model for the role of ER in the prevention and treatment of childhood obesity. A narrative review of the literature by electronic database search (MEDLINE, Web of Knowledge and Scopus) was conducted of observational and interventional/experimental literature on ER and obesity and the underlying concepts. We also present an overview of ER intervention techniques. Our model indicates that childhood ER is a link between stress and obesity. Stress along with ineffective ER leads to abnormal cortisol patterns, emotional eating, sedentary lifestyle, reduction of physical activity, and sleep problems. Simultaneously, a healthy lifestyle could show benefits on ER and in developing adaptive ER strategies. In the development of obesity and ER, parents also play a role. By contrast, effective ER skills decrease obesity-related unhealthy behaviour and enhance protective factors, which boost health. The literature contains some observational studies of children but very few intervention studies, most of which are pilot or on-going studies. In conclusion, encouraging effective ER could be a useful new approach for combating and treating childhood obesity. Future ER intervention studies are needed to confirm the validity of this model in children.

Cue exposure therapy reduces overeating of exposed and non-exposed foods in obese adolescents

BACKGROUND AND OBJECTIVES

This study tested whether two sessions of food cue exposure therapy reduced eating in the absence of hunger (EAH), specified for exposed and non-exposed food, in overweight and obese adolescents, and whether habituation of food cue reactivity and reduced CS-US expectancies predicted a decrease in EAH.

METHODS

41 overweight adolescents (aged 12-18 years) were randomly assigned to a cue exposure intervention or a lifestyle intervention (control condition). Habituation of food cue reactivity (self-reported desire to eat and salivation) and CS-US expectancy were measured during both sessions, and EAH was measured at the end of session two.

RESULTS

Compared to the control condition, the cue exposure condition showed less EAH for the exposed food item as well as for the non-exposed food items. Larger within-session (WSH) and between-session habituation (BSH) of cue reactivity were not related to less EAH, change in CS-US expectancy was unrelated to EAH.

LIMITATIONS

The study was underpowered, and compliance to homework instructions between sessions was poor, intervention effects might have been larger when participants adhered to daily homework exercises.

CONCLUSIONS

Food cue exposure was effective to reduce EAH of exposed and non-exposed food items, indicating generalisability of the exposure effect. In line with exposure effects in anxiety disorders, habituation was not found to benefit outcome, though the present data do also not provide evidence that CS-US expectancy violation predicts EAH.

Effect of combined naltrexone and bupropion therapy on the brain's functional connectivity

Background

The control of food intake in environments with easy access to highly rewarding foods is challenging to most modern societies. The combination of sustained release (SR) naltrexone and SR bupropion (NB32) has been used in weight-loss and obesity management. However, the effects of NB32 on the brain circuits implicated in the regulation of food intake are unknown. Here we used functional connectivity density (FCD) mapping to evaluate the effects of NB32 on resting brain FC.

Methods

Thirty-six healthy women underwent magnetic resonance imaging (MRI) before and after 4-week treatment with NB32 (n = 16) or with placebo (n = 20). In each imaging visit, a 5-min resting-state functional MRI scan was conducted after 15 h of fasting. The FC of brain regions showing significant group effects on FCD were subsequently assessed using seed-voxel correlation analyses. We characterized the associations between FCD measures and craving control scores in the Control of Eating Questionnaire.

Results

After NB32 treatment, the group showed lower local and global FCD than the placebo group in the right superior parietal cortex and lower local FCD in the left middle frontal gyrus. Seed-voxel correlation analysis for the right superior parietal cortex seed demonstrated higher positive FC with the dorsal anterior cingulate gyrus (ACC), bilateral insula, and left superior parietal gyrus and stronger negative FC with right inferior frontal gyrus and right superior parietal cortices for the NB32 than the placebo group. Further, the NB32 group showed a significant correlation between local FCD change after treatment in left middle frontal gyrus and craving control scores (r = 0.519, p = 0.039).

Conclusions

NB32 treatment decreased local and global FCD in superior parietal cortex and increased its connectivity with ACC (involved with saliency attribution), insula (interoception), and decreased local FCD in the medial prefrontal cortex (craving), which might underlie NB32 improved control over eating behaviors. ClinicalTrails.gov: NCT00711.

Brain response to food cues varying in portion size is associated with individual differences in the portion size effect in children

Large portions promote intake of energy dense foods (i.e., the portion size effect--PSE), but the neurobiological drivers of this effect are not known. We tested the association between blood oxygen level dependent (BOLD) brain response to food images varied by portion size (PS) and energy density (ED) and children's intake at test-meals of high- and low-ED foods served at varying portions. Children (N = 47; age 7-10 years) participated in a within-subjects, crossover study consisting of 4 meals of increasing PS of high- and low-ED foods and 1 fMRI to evaluate food images at 2 levels of PS (Large, Small) and 2 levels of ED (High, Low). Contrast values between PS conditions (e.g., Large PS - Small PS) were calculated from BOLD signal in brain regions implicated in cognitive control and reward and input as covariates in mixed models to determine if they moderated the PSE curve. Results showed a significant effect of PS on intake. Responses to Large relative to Small PS in brain regions implicated in salience (e.g., ventromedial prefrontal cortex and orbitofrontal cortex) were positively associated with the linear slope (i.e., increase in intake from baseline) of the PSE curve, but negatively associated with the quadratic coefficient for the total meal. Responses to Large PS High ED relative to Small PS High ED cues in regions associated with cognitive control (e.g., dorsolateral prefrontal cortex) were negatively associated with the linear slope of the PSE curve for high-ED foods. Brain responses to PS cues were associated with individual differences in children's susceptibility to overeating from large portions. Responses in food salience regions positively associated with PSE susceptibility while activation in control regions negatively associated with PSE susceptibility.

How brain response and eating habits modulate food energy estimation

The estimates we do of the energy content of different foods tend to be inaccurate, depending on several factors. The elements influencing such evaluation are related to the differences in the portion size of the foods shown, their energy density (kcal/g), but also to individual differences of the estimators, such as their body-mass index (BMI) or eating habits. Within this context the contribution of brain regions involved in food-related decisions to the energy estimation process is still poorly understood. Here, normal-weight and overweight/obese women with restrained or non-restrained eating habits, received anodal transcranial direct current stimulation (AtDCS) to modulate the activity of the left dorsolateral prefrontal cortex (dlPFC) while they performed a food energy estimation task. Participants were asked to judge the energy content of food images, unaware that all foods, for the quantity presented, shared the same energy content. Results showed that food energy density was a reliable predictor of their energy content estimates, suggesting that participants relied on their knowledge about the food energy density as a proxy for estimating food energy content. The neuromodulation of the dlPFC interacted with individual differences in restrained eating, increasing the precision of the energy content estimates in participants with higher scores in the restrained eating scale. Our study highlights the importance of eating habits, such as restrained eating, in modulating the activity of the left dlPFC during food appraisal.

Youth's Conceptions of Adolescence Predict Longitudinal Changes in Prefrontal Cortex Activation and Risk Taking During Adolescence

The development of cognitive control during adolescence is paralleled by changes in the function of the lateral prefrontal cortex (PFC). Using a three-wave longitudinal neuroimaging design (N = 22, M_age  = 13.08 years at Wave 1), this study examined if youth's stereotypes about teens modulate changes in their neural activation during cognitive control. Participants holding stereotypes of teens as irresponsible in the family context (i.e., ignoring family obligations) in middle school showed increases in bilateral ventrolateral PFC activation during cognitive control over the transition to high school, which was associated with increases in risk taking. These findings provide preliminary evidence that youth's conceptions of adolescence play a role in neural plasticity over this phase of development.

Neuroendocrinology and brain imaging of reward in eating disorders: A possible key to the treatment of anorexia nervosa and bulimia nervosa

Anorexia nervosa and bulimia nervosa are severe eating disorders whose etiopathogenesis is still unknown. Clinical features suggest that eating disorders may develop as reward-dependent syndromes, since eating less food is perceived as rewarding in anorexia nervosa while consumption of large amounts of food during binge episodes in bulimia nervosa aims at reducing the patient's negative emotional states. Therefore, brain reward mechanisms have been a major focus of research in the attempt to contribute to the comprehension of the pathophysiology of these disorders. Structural brain imaging data provided the evidence that brain reward circuits may be altered in patients with anorexia or bulimia nervosa. Similarly, functional brain imaging studies exploring the activation of brain reward circuits by food stimuli as well as by stimuli recognized to be potentially rewarding for eating disordered patients, such as body image cues or stimuli related to food deprivation and physical hyperactivity, showed several dysfunctions in ED patients. Moreover, very recently, it has been demonstrated that some of the biochemical homeostatic modulators of eating behavior are also implicated in the regulation of food-related and non-food-related reward, representing a possible link between the aberrant behaviors of ED subjects and their hypothesized deranged reward processes. In particular, changes in leptin and ghrelin occur in patients with anorexia or bulimia nervosa and have been suggested to represent not only homeostatic adaptations to an altered energy balance but to contribute also to the acquisition and/or maintenance of persistent starvation, binge eating and physical hyperactivity, which are potentially rewarding for ED patients. On the basis of such findings new pathogenetic models of EDs have been proposed, and these models may provide new theoretical basis for the development of innovative treatment strategies, either psychological and pharmacological, with the aim to improve the outcomes of so severe disabling disorders.

An insulin resistance associated neural correlate of impulsivity in type 2 diabetes mellitus

Central insulin resistance (IR) influences striatal dopamine (DA) tone, an important determinant of behavioral self-regulation. We hypothesized that an association exists between the degree of peripheral IR and impulse control, mediated by the impact of IR on brain circuits controlling the speed of executing “go” and/or “stop” responses. We measured brain activation and associated performance on a stop signal task (SST) in obese adults with type 2 diabetes (age, 48.1 ± 6.9 yrs (mean ± SD); BMI, 36.5 ± 4.0 kg/m²; HOMA-IR, 7.2 ± 4.1; 12 male, 18 female). Increasing IR, but not BMI, was a predictor of shorter critical stop signal delay (cSSD), a measure of the time window during which a go response can be successfully countermanded (R² = 0.12). This decline was explained by an IR-associated increase in go speed (R² = 0.13) with little impact of IR or BMI on stop speed. Greater striatal fMRI activation contrast in stop error (SE) compared with stop success (SS) trials (CON_SE>SS) was a significant predictor of faster go speeds (R² = 0.33, p = 0.002), and was itself predicted by greater IR (CON_SE>SS vs HOMA-IR: R² = 0.10, p = 0.04). Furthermore, this impact of IR on striatal activation was a significant mediator of the faster go speeds and greater impulsivity observed with greater IR. These findings suggest a neural mechanism by which IR may increase impulsivity and degrade behavioral self-regulation.

Obesity, Appetite, and the Prefrontal Cortex

PURPOSE OF REVIEW

Obesity is a chronic illness and its prevalence is growing worldwide and numerous factors play a role in the regulation of food intake. The prefrontal cortex (PFC) is involved in high-order executive function, regulation of limbic reward regions, and the inhibition of impulsive behaviors. Understanding the role of the PFC in the control of appetite regulation may contribute to a greater understanding of the etiology of obesity and could improve weight loss outcomes.

RECENT FINDINGS

Neuroimaging studies have identified lower activation in the left dorsolateral PFC (DLPFC) in obese compared to lean individuals and others have focused on efforts to improve cognitive control in this area of the brain. The DLPFC is a critical brain area associated with appetitive control, food craving, and executive functioning, indicating a candidate target area for treatment. Further studies are needed to advance our understanding of the relationship between obesity, appetite, and the DLPFC and provide validation for the effectiveness of novel treatments in clinical populations.

Role of impulsivity and reward in the anti-obesity actions of 5-HT2C receptor agonists

The selective 5-HT_2C receptor agonist lorcaserin entered clinical obesity trials with the prevalent view that satiety was a primary mechanism of action. Subsequent Phase II and III trials demonstrated efficacy in terms of weight loss, although the overall effect size (~3% placebo-corrected change) is considered modest. Lorcaserin has been approved by the FDA for the treatment of obesity with lifestyle modification, but since its introduction in 2013 its sales are in decline, probably due to its overall modest effect. However, in some individuals, lorcaserin has a much more clinically significant effect (i.e. >10% placebo-corrected change), although what common features, if any, define these high responders is presently unknown. In the present article we highlight the evidence that alternative mechanisms to satiety may contribute to the anti-obesity effect of lorcaserin, namely effects on constructs of primary and conditioned reward and impulsivity. This may better inform the clinical evaluation of lorcaserin (and any future 5-HT_2C receptor agonists) to subgroups of obese subjects characterized by overeating due to maladaptive impulsivity and reward mechanisms. One such population might be individuals diagnosed with binge eating disorder.

Ovarian hormones and obesity

BACKGROUND

Obesity is caused by an imbalance between energy intake, i.e. eating and energy expenditure (EE). Severe obesity is more prevalent in women than men worldwide, and obesity pathophysiology and the resultant obesity-related disease risks differ in women and men. The underlying mechanisms are largely unknown. Pre-clinical and clinical research indicate that ovarian hormones may play a major role.

OBJECTIVE AND RATIONALE

We systematically reviewed the clinical and pre-clinical literature on the effects of ovarian hormones on the physiology of adipose tissue (AT) and the regulation of AT mass by energy intake and EE.

SEARCH METHODS

Articles in English indexed in PubMed through January 2016 were searched using keywords related to: (i) reproductive hormones, (ii) weight regulation and (iii) central nervous system. We sought to identify emerging research foci with clinical translational potential rather than to provide a comprehensive review.

OUTCOMES

We find that estrogens play a leading role in the causes and consequences of female obesity. With respect to adiposity, estrogens synergize with AT genes to increase gluteofemoral subcutaneous AT mass and decrease central AT mass in reproductive-age women, which leads to protective cardiometabolic effects. Loss of estrogens after menopause, independent of aging, increases total AT mass and decreases lean body mass, so that there is little net effect on body weight. Menopause also partially reverses women's protective AT distribution. These effects can be counteracted by estrogen treatment. With respect to eating, increasing estrogen levels progressively decrease eating during the follicular and peri-ovulatory phases of the menstrual cycle. Progestin levels are associated with eating during the luteal phase, but there does not appear to be a causal relationship. Progestins may increase binge eating and eating stimulated by negative emotional states during the luteal phase. Pre-clinical research indicates that one mechanism for the pre-ovulatory decrease in eating is a central action of estrogens to increase the satiating potency of the gastrointestinal hormone cholecystokinin. Another mechanism involves a decrease in the preference for sweet foods during the follicular phase. Genetic defects in brain α-melanocycte-stimulating hormone-melanocortin receptor (melanocortin 4 receptor, MC4R) signaling lead to a syndrome of overeating and obesity that is particularly pronounced in women and in female animals. The syndrome appears around puberty in mice with genetic deletions of MC4R, suggesting a role of ovarian hormones. Emerging functional brain-imaging data indicates that fluctuations in ovarian hormones affect eating by influencing striatal dopaminergic processing of flavor hedonics and lateral prefrontal cortex processing of cognitive inhibitory controls of eating. There is a dearth of research on the neuroendocrine control of eating after menopause. There is also comparatively little research on the effects of ovarian hormones on EE, although changes in ovarian hormone levels during the menstrual cycle do affect resting EE.

WIDER IMPLICATIONS

The markedly greater obesity burden in women makes understanding the diverse effects of ovarian hormones on eating, EE and body adiposity urgent research challenges. A variety of research modalities can be used to investigate these effects in women, and most of the mechanisms reviewed are accessible in animal models. Therefore, human and translational research on the roles of ovarian hormones in women's obesity and its causes should be intensified to gain further mechanistic insights that may ultimately be translated into novel anti-obesity therapies and thereby improve women's health.

Motor skill experience modulates executive control for task switching

This study aimed to investigate the effect of types of motor skills, including open and closed skills on enhancing proactive and reactive controls for task switching. Thirty-six athletes in open (n=18) or closed (n=18) sports and a control group (n=18) completed the task-switching paradigm and the simple reaction task. The task-switching paradigm drew on the proactive and reactive control of executive functions, whereas the simple reaction task assessed the processing speed. Significant Validity×Group effect revealed that the participants with open skills had a lower switch cost of response time compared to the other two groups when the task cue was 100% valid; whereas the participants regardless of motor skills had a lower switch cost of response time compared to the control group when the task cue was 50% valid. Hierarchical stepwise regression analysis further confirmed these findings. For the simple reaction task, there were no differences found among the three groups. These findings suggest that experience in open skills has benefits of promoting both proactive and reactive controls for task switching, which corresponds to the activity context exposed by the participants. In contrast, experience in closed skills appears to only benefit development of reactive control for task switching. The neural mechanisms for the proactive and reactive controls of executive functions between experts with open and closed skills call for future study.

Contributions of polygenic risk for obesity to PTSD-related metabolic syndrome and cortical thickness

BACKGROUND

Research suggests that posttraumatic stress disorder (PTSD) is associated with metabolic syndrome (MetS) and that PTSD-associated MetS is related to decreased cortical thickness. However, the role of genetic factors in these associations is unclear. This study evaluated contributions of polygenic obesity risk and PTSD to MetS and of MetS and polygenic obesity risk to cortical thickness.

METHODS

196 white, non-Hispanic veterans of the wars in Iraq and Afghanistan underwent clinical diagnostic interviews, physiological assessments, and genome-wide genotyping; 168 also completed magnetic resonance imaging scans. Polygenic risk scores (PRSs) for obesity were calculated from results of a prior genome-wide association study (Speliotes et al., 2010) and PTSD and MetS severity factor scores were obtained.

RESULTS

Obesity PRS (β=0.15, p=0.009) and PTSD (β=0.17, p=0.005) predicted MetS and interacted such that the association between PTSD and MetS was stronger in individuals with greater polygenic obesity risk (β=0.13, p=0.02). Whole-brain vertex-wise analyses suggested that obesity PRS interacted with MetS to predict decreased cortical thickness in left rostral middle frontal gyrus (β=-0.40, p<0.001).

CONCLUSIONS

Results suggest that PTSD, genetic variability, and MetS are related in a transactional fashion wherein obesity genetic risk increases stress-related metabolic pathology, and compounds the ill health effects of MetS on the brain. Genetic proclivity towards MetS should be considered in PTSD patients when prescribing psychotropic medications with adverse metabolic profiles. Results are consistent with a growing literature suggestive of PTSD-related accelerated aging.

The value of instability: an investigation of intrasubject variability in brain activity among obese adolescent girls

BACKGROUND

The present study investigated the value of intrasubject variability (ISV) as a metric for revealing differences in cognition and brain activation associated with an obese versus lean body mass.

METHODS

Ninety-six adolescents with a lean body mass (body mass index (BMI) percentile=5-85), and 92 adolescents with an obese body mass (BMI percentile ⩾95), performed two tasks (Stroop and Go/No-Go) challenging response inhibition skills. The s.d. values and averages of their reaction time and P300 electroencephalographic responses to task stimuli were computed across trials.

RESULTS

During the Go/No-Go task, the reaction times of subjects with an obese body mass were more variable than those of their lean body mass peers. Accompanying the greater ISV in reaction times was a group difference in P300 amplitude ISV in the opposite direction across both tasks. The effect sizes associated with these group differences in ISV were marginally greater than the effect sizes for the comparisons of the group means.

CONCLUSIONS

ISV may be superior to the mean as a tool for differentiating groups without significant cognitive impairment. The co-occurrence of reduced ISV in P300 amplitude and elevated ISV in reaction time may indicate a constraint among obese adolescent girls in the range of information processing strategies and neural networks that can compete to optimize response output. It remains to be determined whether this decrement in neural plasticity has implications for their problem solving skills as well as their response to weight management interventions.

Effect of Soy and Soy Isoflavones on Obesity-Related Anthropometric Measures: A Systematic Review and Meta-analysis of Randomized Controlled Clinical Trials

Soy may be a suitable food for anti-obesity efforts because of its high protein and isoflavone content. We conducted this meta-analysis to evaluate potential effects of soy and soy isoflavones on weight, waist circumference, and fat mass. PubMed, MEDLINE, Scopus, EMBASE, and Cochrane databases were searched. Twenty-four trials with soy and 17 trials with isoflavones passed the eligibility stage. According to the results, soy showed no overall statistically significant effect on weight, waist circumference, or fat mass, but a significant increasing effect on weight was observed in some circumstances: for instance, in obese subjects [mean difference (MD): 0.80 kg; 95% CI: 0.15, 1.45 kg; P = 0.02], with ingestions of ≥40 g soy protein/d (MD: 0.94 kg; 95% CI: 0.11, 1.77 kg; P = 0.03), with short-term applications (1-3 mo) (MD: 0.45 kg; 95% CI: 0.05, 0.86 kg; P = 0.03), and when soy was compared with meat (MD: 0.36 kg; 95% CI: 0.09, 0.64 kg; P = 0.03) and whey protein (MD: 1.53 kg; 95% CI: 0.10, 2.96 kg; P = 0.04). In contrast to the effects of soy on weight, soy significantly decreased waist circumference in older ages (MD: -0.36 cm; 95% CI: -0.71, -0.01 cm; P = 0.04), in women (MD: -0.32 cm; 95% CI: -0.57, -0.08 cm; P = 0.01), and at doses of <40 g soy protein/d (MD: -0.31 cm; 95% CI: -0.57, -0.05 cm; P = 0.02). Isoflavone studies, conducted only in women, showed that isoflavones may reduce body mass index (BMI; in kg/m2) (MD: -0.26; 95% CI: -0.55, 0.04; P = 0.085), especially in dosages <100 mg/d (MD: -0.48; 95% CI: -0.90, -0.06; P = 0.02) and in intervention periods of 2-6 mo (MD: -0.28; 95% CI: -0.56, 0.00; P = 0.053), but no effect was observed in higher doses or longer intervention periods. Also, a trend for reduced BMI after consumption of isoflavones was observed in Caucasians (MD: -0.35; 95% CI: -0.74, 0.04; P = 0.08). Overall, results showed that, although soy is the major source of isoflavones, soy and isoflavones may have different impacts on weight status.

Neuroscience of Compulsive Eating Behavior

A systematic characterization of compulsivity in pathological forms of eating has been proposed in the context of three functional domains: (1) habitual overeating; (2) overeating to relieve a negative emotional state; and (3) overeating despite aversive consequences. In this review, we provide evidence supporting this hypothesis and we differentiate the nascent field of neurocircuits and neurochemical mediators of compulsive eating through their underlying neuropsychobiological processes. A better understanding of the neurobiological mechanisms that lead to compulsive eating behavior can improve behavioral and pharmacological intervention for disorders of pathological eating.