Cognitive and neuromodulation strategies for unhealthy eating and obesity: Systematic review and discussion of neurocognitive mechanisms

Neural activity and connectivity are related to food preference changes induced by food go/no-go training

Simply withholding a response while viewing an appetizing food, over the course of many presentations (i.e., during food go/no-go training) can modify individuals' food preferences-which could, in turn, promote healthier eating behaviors. However, the neural mechanisms underlying this food go/no-go training-induced change in food preferences are still relatively unclear. We addressed this issue in the present functional magnetic resonance imaging (fMRI) study. To this end, we administered a novel passive viewing task before and after food go/no-go training to 91 participants in the scanner. Participants' food preferences were measured with a binary food choice task. At the behavioral level, we found the expected training effect on food preferences: Participants preferred go over no-go foods following training. At the neural level, we found that changes in food preferences were associated with training-related go vs. no-go differences in activity and functional connectivity, such as less activity in the anterior cingulate cortex and superior frontal gyrus but greater functional connectivity between the superior frontal gyrus and middle occipital gyrus. Critically, Dynamic causal modeling showed that this preference change effect was largely driven by top-down influence from the superior frontal gyrus to the middle occipital gyrus. Together, these findings suggest a neural mechanism of the food go/no-go training effect-namely, that the food-viewing-related interplay between prefrontal regions and visual regions might be related to the food preference change following food go/no-go training.

Food-related inhibitory control deficits in young male adults with obesity: Behavioral and ERP evidence from a food-related go/no-go task

PURPOSE

Obesity poses a pervasive challenge to global public health, which is linked to adverse physical health outcomes and cognitive decline. Cognitive function, particularly food-related cognitive function, plays a critical role in sustaining a healthy weight and mitigating the progression of obesity. The aim of this study was to investigate the behavioral and neuroelectronic aspects of food-related inhibitory functions in young adult males with obesity.

METHODS

Forty-nine participants with obesity and healthy-weight were recruited (BMI = 35.83 ± 5.06 kg/m2 vs. 22.55 ± 1.73 kg/m2, age = 24.23 ± 4.55 years vs. 26.00 ± 3.97 years). A food-related Go/No-go task which included 6 distinct blocks in a randomized order was conducted to investigate the general and food-related inhibitory control. 180 stimulus images from the Food Picture Database encompassing high-calorie food, low-calorie food, and neutral images were selected. Behavioral (Go RT, Go ACC, No-go ACC) and event-related potential measures (N2 and P3 amplitude) during the food-related Go/No-go task were measured.

RESULTS

The main findings indicated that the group with obesity exhibited lower No-go accuracy, slower go reaction times, and smaller P3 amplitudes in high-calorie, low-calorie foods, and neutral picture, compared to the normal-weight group, but with no group difference in N2. Additionally, high-calorie food induced larger N2 and P3 amplitude than the neutral stimuli.

CONCLUSIONS

Young male adults with obesity exhibit poorer inhibitory control in both food and non-food domains, specifically in slower reaction time and reduced accuracy, featuring difficulties in neural resource recruitment during the inhibitory control process. Additionally, the P3 component could serve as sensitive indicators to reveal the neural mechanisms of inhibitory control deficits in obesity, while the N2 and P3 components may differentiate the neural differences between high-calorie foods and non-foods in inhibitory control processing. Food, especially high-calorie food, induces more neural resources and may exacerbate the poor inhibitory ability towards food in obesity. Targeted interventions such as exercise interventions, cognitive training as well as neuromodulation interventions are warranted in the future to improve impaired general and food-related inhibitory functions in the obese populations, offering both theoretical and practical frameworks for obesity prevention and treatment.

Testing Go/No-Go training effects on implicit evaluations of unhealthy and healthy snack foods

OBJECTIVE

Despite intending to eat healthy foods, people often yield to temptation. In environments rife with unhealthy food options, a positive implicit evaluation of unhealthy foods may inadvertently influence unhealthy choices. This study investigates if and under which conditions implicit evaluations of unhealthy and healthy foods can be influenced by a computer-based Go/No-Go (GNG) training.

DESIGN

Undergraduate student participants (N = 161 participants; 117 females, 44 males; Mage = 19 years, SD = 2 years) completed a GNG training with two healthy (grape and nut) and two unhealthy (potato chip and cookie) stimuli. Participants were either instructed to inhibit their responses to the potato chip (No-Go Chips/Go Grape) or to a grape (No-Go Grape/Go Chips).

MAIN OUTCOME MEASURE

Implicit evaluations of chips and grapes were assessed using the Extrinsic Affective Simon Task.

RESULTS

This GNG training impacted implicit evaluations of chips, but not grapes. GNG training effects were stronger for participants with lower sensitivity for behavioural inhibition measured with the Behavioural Inhibition System scale.

CONCLUSION

GNG training might help people change implicit food evaluations. More research is needed to understand how individual and training characteristics affect outcomes with the goal of tailoring and optimising the GNG training to produce the strongest effect.

Near-infrared spectroscopy and electroencephalography neurofeedback for binge-eating disorder: an exploratory randomized trial

BACKGROUND

Binge-eating disorder (BED) co-occurs with neurobehavioral alterations in the processing of disorder-relevant content such as visual food stimuli. Whether neurofeedback (NF) directly targeting them is suited for treatment remains unclear. This study sought to determine feasibility and estimate effects of individualized, functional near-infrared spectroscopy-based real-time NF (rtfNIRS-NF) and high-beta electroencephalography-based NF (EEG-NF), assuming superiority over waitlist (WL).

METHODS

Single-center, assessor-blinded feasibility study with randomization to rtfNIRS-NF, EEG-NF, or WL and assessments at baseline (t0), postassessment (t1), and 6-month follow-up (t2). NF comprised 12 60-min food-specific rtfNIRS-NF or EEG-NF sessions over 8 weeks. Primary outcome was the binge-eating frequency at t1 assessed interview-based. Secondary outcomes included feasibility, eating disorder symptoms, mental and physical health, weight management-related behavior, executive functions, and brain activity at t1 and t2.

RESULTS

In 72 patients (intent-to-treat), the results showed feasibility of NF regarding recruitment, attrition, adherence, compliance, acceptance, and assessment completion. Binge eating improved at t1 by -8.0 episodes, without superiority of NF v. WL (-0.8 episodes, 95% CI -2.4 to 4.0), but with improved estimates in NF at t2 relative to t1. NF was better than WL for food craving, anxiety symptoms, and body mass index, but overall effects were mostly small. Brain activity changes were near zero.

CONCLUSIONS

The results show feasibility of food-specific rtfNIRS-NF and EEG-NF in BED, and no posttreatment differences v. WL, but possible continued improvement of binge eating. Confirmatory and mechanistic evidence is warranted in a double-blind randomized design with long-term follow-up, considering dose-response relationships and modes of delivery.

Mechanisms underlying fNIRS-neurofeedback over the prefrontal cortex for participants with binge-eating disorder

OBJECTIVE

Despite the increasing popularity of neurofeedback (NF), aiming at voluntary modulation of dysfunctional prefrontal cortex (PFC) signals in the treatment of binge-eating disorder (BED) and/or overweight, mechanisms remain poorly understood.

METHODS

Based on a randomized-controlled trial offering 12 food-specific real-time functional near-infrared spectroscopy (rtfNIRS)-NF sessions to participants with BED (n = 22), this preregistered study examined (1) online regulation success as predictor for offline regulation success, defined by PFC signals during regulation versus watch, and subjective regulation success, and (2) changes in loss of control (LOC) eating after vs. before and across 12 rtfNIRS-NF-sessions.

RESULTS

Higher online regulation success expectedly predicted better subjective, but worse offline regulation success. LOC eating decreased after vs. before, but not over rtfNIRS-NF-sessions, and was not associated with subjective or offline regulation success.

CONCLUSIONS

The association between online and subjective regulation success confirmed the presumed mechanism of operant conditioning underlying rtfNIRS-NF-learning. The contrary association between online and offline regulation indicated differential PFC involvement upon subtraction of automatic food-specific responses from regulation signals for offline success. Decreased LOC eating after food-specific rtfNIRS-NF-sessions suggested the potential of NF in BED treatment.

SIGNIFICANCE

Results may guide the optimization of future NF studies in larger samples with BED.

Predictors of neurofeedback treatment outcome in binge-eating disorder: An exploratory study

OBJECTIVE

Knowledge on predictors for treatment response to psychotherapy in binge-eating disorder (BED) is mixed and not yet available for increasingly popular neurofeedback (NF) treatment targeting self-regulation of aberrant brain activity. This study examined eating disorder- and psychopathology-related predictors for NF treatment success in BED.

METHOD

Patients with BED (N = 78) were randomized to 12 sessions of real-time functional near-infrared spectroscopy (rtfNIRS)-NF, targeting individual prefrontal cortex signal up-regulation, electroencephalography (EEG)-NF, targeting down-regulation of fronto-central beta activity, or waitlist (WL). The few studies assessing predictors for clinical outcomes after NF and evidenced predictors for psychotherapy guided the selection of baseline eating disorder-related predictors, including objective binge-eating (OBE) frequency, eating disorder psychopathology (EDP), food cravings, and body mass index (BMI), and general psychopathology-related predictors, including depressive and anxiety symptoms, impulsivity, emotion dysregulation, and self-efficacy. These questionnaire-based or objectively assessed (BMI) predictors were regressed on outcomes OBE frequency and EDP as key features of BED at post-treatment (t1) and 6-month follow-up (t2) in preregistered generalized mixed models (https://osf.io/4aktp).

RESULTS

Higher EDP, food cravings, and BMI predicted worse outcomes across all groups at t1 and t2. General psychopathology-related predictors did not predict outcomes at t1 and t2. Explorative analyses indicated that lower OBE frequency and higher self-efficacy predicted lower OBE frequency, and lower EDP predicted lower EDP after the waiting period in WL.

DISCUSSION

Consistent with findings for psychotherapy, higher eating disorder-related predictors were associated with higher EDP and OBE frequency. The specificity of psychopathological predictors for NF treatment success warrants further examination.

PUBLIC SIGNIFICANCE

This exploratory study firstly assessed eating disorder- and psychopathology-related predictors for neurofeedback treatment outcome in binge-eating disorder and overweight. Findings showed an association between higher eating disorder symptoms and worse neurofeedback outcomes, indicating special needs to be considered in neurofeedback treatment for patients with a higher binge-eating disorder symptom burden. In general, outcomes and assignment to neurofeedback treatment may be improved upon consideration of baseline psychological variables.

Connectome-based prediction of eating disorder-associated symptomatology

BACKGROUND

Despite increasing knowledge on the neuroimaging patterns of eating disorder (ED) symptoms in non-clinical populations, studies using whole-brain machine learning to identify connectome-based neuromarkers of ED symptomatology are absent. This study examined the association of connectivity within and between large-scale functional networks with specific symptomatic behaviors and cognitions using connectome-based predictive modeling (CPM).

METHODS

CPM with ten-fold cross-validation was carried out to probe functional networks that were predictive of ED-associated symptomatology, including body image concerns, binge eating, and compensatory behaviors, within the discovery sample of 660 participants. The predictive ability of the identified networks was validated using an independent sample of 821 participants.

RESULTS

The connectivity predictive of body image concerns was identified within and between networks implicated in cognitive control (frontoparietal and medial frontal), reward sensitivity (subcortical), and visual perception (visual). Crucially, the set of connections in the positive network related to body image concerns identified in one sample was generalized to predict body image concerns in an independent sample, suggesting the replicability of this effect.

CONCLUSIONS

These findings point to the feasibility of using the functional connectome to predict ED symptomatology in the general population and provide the first evidence that functional interplay among distributed networks predicts body shape/weight concerns.

Psychological and Medical Treatments for Binge-Eating Disorder: A Research Update

Binge-eating disorder (BED), characterized by recurrent binge eating in the absence of regular weight-compensatory behaviors, is the most common eating disorder, associated with pronounced mental and physical sequelae. An increasing body of research documents the efficacy of diverse approaches to the treatment of this disorder, summarized in meta-analyses. This research update narratively reviewed randomized-controlled trials (RCTs) on the psychological and medical treatment of BED published between January 2018 to November 2022, identified through a systematic literature search. A total of 16 new RCTs and 3 studies on previous RCTs providing efficacy- and safety-related data were included. Regarding psychotherapy, confirmatory evidence supported the use of integrative-cognitive therapy and, with lower effects, brief emotion regulation skills training for binge eating and associated psychopathology. Behavioral weight loss treatment was revealed to be efficacious for binge eating, weight loss, and psychopathology, but its combination with naltrexone-bupropion did not augment efficacy. New treatment approaches were explored, including e-mental-health and brain-directed treatments, mostly targeting emotion and self-regulation. Additionally, different therapeutic approaches were evaluated in complex stepped-care models. In light of these advances, future research is necessary to further optimize effects of evidence-based treatments for BED, through improvement of existing or development of new treatments, based on mechanistic and/or interventional research, and/or tailoring treatments to personal characteristics in a precision medicine approach.

Long-term effects of repeated multitarget high-definition transcranial direct current stimulation combined with cognitive training on response inhibition gains

Background

Few studies have investigated the effects of repeated sessions of transcranial direct current stimulation (tDCS) combined with concurrent cognitive training on improving response inhibition, and the findings have been heterogeneous in the limited research. This study investigated the long-lasting and transfer effects of 10 consecutive sessions of multitarget anodal HD-tDCS combined with concurrent cognitive training on improving response inhibition compared with multitarget stimulation or training alone.

Methods

Ninety-four healthy university students aged 18–25 were randomly assigned to undergo different interventions, including real stimulation combined with stop-signal task (SST) training, real stimulation, sham stimulation combined with SST training, and sham stimulation. Each intervention lasted 20 min daily for 10 consecutive days, and the stimulation protocol targeted right inferior frontal gyrus (rIFG) and pre-supplementary motor area (pre-SMA) simultaneously with a total current intensity of 2.5 mA. Performance on SST and possible transfer effects to Stroop task, attention network test, and N-back task were measured before and 1 day and 1 month after completing the intervention course.

Results

The main findings showed that the combined protocol and the stimulation alone significantly reduced stop-signal reaction time (SSRT) in the post-intervention and follow-up tests compared to the pre-intervention test. However, training alone only decreased SSRT in the post-test. The sham control exhibited no changes. Subgroup analysis revealed that the combined protocol and the stimulation alone induced a decrease in the SSRT of the low-performance subgroup at the post-test and follow-up test compared with the pre-test. However, only the combined protocol, but not the stimulation alone, improved the SSRT of the high-performance subgroup. The transfer effects were absent.

Conclusion

This study provides supportive evidence for the synergistic effect of the combined protocol, indicating its superiority over the single intervention method. In addition, the long-term after-effects can persist for up to at least 1 month. Our findings also provide insights into the clinical application and strategy for treating response inhibition deficits.

Pilot study of food-specific go/no-go training for overweight individuals: brain imaging data suggest inhibition shapes food evaluation

Food-specific go/no-go training might reduce overeating and facilitate weight loss. In this pilot study, we examined whether a food-specific go/no-go training over five weeks, as compared to a non-food-specific training, could produce changes in behavioral and neural responses to food images and body weight. Here, we used a sample of 51 overweight participants divided into training and control groups whose brain activity and food evaluation were measured before and after the training. Compared with the control group, in the training group we found significant reductions in high-calorie food evaluation. We also found lower activations in inhibitory control- and reward-related brain regions in response to high-calorie food images. Further, activation change of the mid-insula in response to the high-calorie food images was positively associated with change in the evaluation of those images. However, we found no evidence for a significant effect of food-specific go/no-go training on body weight change. Our findings highlight that food-specific go/no-go training in overweight individuals can reduce high-calorie food evaluation, but also neural activations in inhibitory control- and reward- related brain regions.

Improving adult eating behaviours by manipulating time perspective: a systematic review and meta-analysis

There is a growing body of research on improving health behaviours through future thinking but that in improving eating behaviour remains unclear. Hence, we conducted a systematic review and meta-analysis on the effectiveness of time perspective manipulation in improving adult eating behaviours. Articles published from inception through 17 March 2022 were retrieved from eight databases (CINAHL, Embase, ProQuest, PsycINFO, PubMed, Scopus, The Cochrane library, and Web of Science). Meta-analysis was conducted using random effects models with effect sizes reported in Hedges' g. Sixteen experimental studies were included, representing 1,914 participants with mean ages ranging from 20.5 to 44.1 years old and mean baseline BMI of 22.0 kg/m2 to 37.2 kg/m2. The interventions included were episodic future thinking (EFT; n = 12), message framing (n = 2), and varying inter-meal intervals (IMI; n = 2) in improving food choices, food intake and portion size. Two studies reported significant interventional effectiveness for domain-specific EFT while all studies on message framing and IMI reported significant interventional effectiveness. Message framing seemed to be more effective when both temporal distance and valence frames were manipulated. However, the pooled effect sizes of all the interventions did not result in a significant interventional effect (n = 5; g = -0.49; 95% confidence interval (CI) = -1.44, 0.47; p = 0.23; I2=87.2%). More rigorous research is needed to ascertain the effectiveness of manipulating time perspective in improving eating behaviours before such interventions are more widely used.

Trait Anxiety and Unhealthy Eating in Adult Women: The Mediating Role of Cognitive Instability

Previous studies have demonstrated the influence of affective states on unhealthy eating. Heightened impulsivity has also been recognized as a risk factor for unhealthy eating. The objective of the present study was to investigate the relationship between trait anxiety and unhealthy eating and to test whether cognitive instability (trait impulsivity component) might mediate this relationship among adult women.

METHOD

The sample was composed of 225 women (M_age = 29.70 ± 9.23; M_{BodyMass Index} = 23.39 ± 4.43). The State-Trait Anxiety Inventory (STAI), the Food Frequency Questionnaire (FFQ), and the Barratt Impulsiveness Scale (BIS) were used. We first conducted a principal components analysis to reduce the dimensionality of the FFQ data, finding four principal components. For our primary analyses, we focused on unhealthy eating. We then conducted a mediation analysis to examine whether trait anxiety was associated with unhealthy eating and, if so, whether cognitive impulsivity mediated this relationship.

RESULTS

Trait anxiety was positively associated with cognitive instability, and cognitive instability was positively associated with unhealthy eating. Trait anxiety was also positively associated with unhealthy eating, but only when controlling for cognitive instability. Consistent with our proposed mediation model, trait anxiety was positively associated with cognitive instability, which in turn predicted unhealthy eating among adult women.

CONCLUSION

Adult women who reported higher levels of trait anxiety experienced higher levels of cognitive instability and engaged in poor dietary behaviors. Identifying the factors related to unhealthy eating represents a crucial step toward findings ways of reducing their impact on food intake and replacing them with more productive ones.

The effects of prefrontal vs. parietal cortex transcranial direct current stimulation on craving, inhibition, and measures of self-esteem

While prefrontal cortex dysfunction has been implicated in high food cravings, other cortical regions, like the parietal cortex, are potentially also involved in regulating craving. This study explored the effects of stimulating the inferior parietal lobule (IPL) and dorsolateral prefrontal cortex (DLPFC) on food craving state and trait. Transcranial direct current stimulation (tDCS) was administered at 1.5 mA for 5 consecutive days. Participants received 20 min of IPL, DLPFC, or sham stimulation (SHAM) each day which consisted of two rounds of 10-min stimulation, divided by a 10-min mindfulness task break. In addition, we studied inhibition and subjective psychological aspects like body image and self-esteem state and trait. To decompose immediate and cumulative effects, we measured the following on days 1 and 5: inhibition through the Go/No-go task; and food craving, self-esteem, and body appreciation through a battery of questionnaires. We found that false alarm errors decreased in the participants receiving active stimulation in the DLPFC (DLPFC-group). In contrast, false alarm errors increased in participants receiving active stimulation in the IPL (IPL-group). At the same time, no change was found in the participants receiving SHAM (SHAM-group). There was a trending reduction in craving trait in all groups. Momentary craving was decreased in the DLPFC-group and increased in IPL-group, yet a statistical difference was not reached. According to time and baseline, self-esteem and body perception improved in the IPL-group. Furthermore, self-esteem trait significantly improved over time in the DLPFC-group and IPL-group. These preliminary results indicate that tDCS modulates inhibition in frontoparietal areas with opposite effects, enhancing it in DLPFC and impairing it in IPL. Moreover, craving is moderately linked to inhibition, self-esteem, and body appreciation which seem not to be affected by neuromodulation but may rely instead on broader regions as more complex constructs. Finally, the fractionated protocol can effectively influence inhibition with milder effects on other constructs.

Attitudes to Three Weight Maintenance Strategies: A Qualitative Study

Weight loss maintenance can be difficult and ultimately unsuccessful, due to psychological, behavioural, social, and physiological influences. The present study investigated three strategies with the potential to improve weight maintenance success: daily weighing, missing an occasional meal, habitually changing high energy foods. The principal aim was to gain an understanding of attitudes to these strategies in participants who had recent experience of weight loss attempts, with or without maintenance. This was a qualitative study involving semi-structured interviews, with 20 participants aged 18–67 (twelve females), analysed using thematic analysis. Most participants disliked daily weighing and missing an occasional meal for long-term maintenance and were concerned about potential negative effects on mental health. All participants had experience of habitual changes to high energy foods and regarded this strategy as obvious and straightforward. Replacement of high energy foods was favoured over elimination. Participants preferred strategies that felt flexible, “normal” and intuitive and disliked those that were thought to have a negative impact on mental health. Further investigation is needed on whether concerns regarding mental health are well founded and, if not, how the strategies can be made more acceptable and useful.

Orbitofrontal neural dissociation of healthy and unhealthy food reward sensitivity in normal-weight binge eaters

OBJECTIVE

The orbitofrontal cortex (OFC) has been repeatedly found to play an important role in food reward processing and binge eating (BE) episodes. However, most studies have focused mainly on reward-related neural alterations in clinical binge eating patients, with little consideration of preclinical individuals with BE that are more likely to develop from non-clinical individuals to clinical patients in the future. This study aimed to examine whether preclinical binge eaters exhibited OFC-related resting-state functional connectivity (rsFC) in the context of food reward.

METHOD

Binge eaters (BE group, n = 28) and healthy controls (HCs, n = 28) matched for age and body mass index (BMI) underwent rs-fMRI scans and completed self-reported assessment of BE symptoms. Food reward sensitivity was measured using the modified food incentive delay task. Analysis of covariance was used to assess the between-group differences in the medial and lateral OFC (a priori selected regions of interest) connectivity patterns in the context of food reward, while controlling for age, sex, and BMI.

RESULTS

Lower unhealthy food (UF) reward sensitivity was significantly associated with stronger inverse OFC-putamen connectivity for HCs, while the BE group showed no association between UF reward sensitivity and the OFC-putamen connectivity. Higher healthy food (HF) reward sensitivity in the BE group was significantly correlated with stronger positive OFC-middle frontal gyrus and OFC-inferior parietal gyrus connectivity, while the opposite was found for HCs.

CONCLUSIONS

Binge eaters showed less functional synchrony within reward regions contributing to the UF reward sensitivity, but enhanced neural interactions between reward and inhibitory control regions correlated with the HF reward sensitivity. These novel findings may demonstrate the potential orbitofrontal neural dissociation of unhealthy and healthy food reward sensitivity in normal-weight binge eaters.

A Program for the Comprehensive Cognitive Training of Excess Weight (TRAINEP): The Study Protocol for A Randomized, Controlled Trial

Background: The available treatments for people with excess weight have shown small effects. Cognitive training has shown promising results, but most of the research focused on normal-weight university students and reported immediate results after a single training session. This parallel group, randomized, controlled trial aims to study the efficacy of a program for the comprehensive cognitive treatment of excess weight. Methods and Analysis: Participants will be 150 people with excess weight recruited through social media, who will be randomized into three groups: cognitive intervention, sham cognitive intervention, and treatment as usual. All assessment and intervention sessions will be online in groups of 5–6 participants. The three groups will attend a motivational interviewing session, and they will receive individualized diet and physical exercise guidelines throughout the program. The cognitive training will consist of four weekly sessions of approximately 60–90 min, each based on approach–avoidance bias training, inhibitory control training, implementation of intentions, and episodic future thinking, respectively. The main outcome measure will be a change in Body Mass Index (kg/m2). Secondary outcomes include changes in cognitive measures, eating and physical exercise behaviors, and anthropometric measures. Assessments will be conducted up to 6 months after the end of the program. In addition, data on the use of the health system will be collected to analyze the cost-effectiveness and the cost-utility of training. Linear mixed models will be used for statistical analysis. Findings of this study will expand the available evidence on cognitive interventions to reduce excess weight.

Food-Specific Inhibition Training for Food Devaluation: A Meta-Analysis

Theories have suggested that food-specific inhibition training could lead to food devaluation which, in turn, may help people to regulate their eating behavior. In this review, we have synthesized the current literature on this topic by conducting a meta-analysis of studies investigating the effects of food-specific inhibition training on food evaluation. We identified 24 studies-with 36 independent samples, 77 effect sizes, and 3032 participants-that met our inclusion criteria. Effect sizes were analyzed using the robust variance estimation in random effects meta-regression technique. The results indicate that food-specific inhibition training can lead to statistically significant reductions in food evaluation. More specifically, it was observed that the effects of training on participants' food evaluation differed according to the type of evaluation; food-specific inhibition training significantly decreased participants' explicit food evaluation, but not their implicit food evaluation. However, because most of the included studies focused on trained food items and short-term outcomes in normal-weight samples, more research is needed on the continuance of the training effects, as well as on the extent to which effects can be generalized to untrained food items or different populations (e.g., overweight or obese individuals).

The evidential value of research on cognitive training to change food-related biases and unhealthy eating behavior: A systematic review and p-curve analysis

Cognitive bias modification (CBM), which retrains implicit biases towards unhealthy foods, has been proposed as a promising adjunct to improve the efficacy of weight loss interventions. We conducted a systematic review of research on three CBM approaches (i.e., cue-specific inhibitory control, approach bias modification, and attentional bias modification) for reducing unhealthy eating biases and behavior. We performed a p-curve analysis to determine the evidential value of this research; this method is optimally suited to clarify whether published results reflect true effects or false positives due to publication and reporting biases. When considering all CBM approaches, our results suggested that the findings of CBM trials targeting unhealthy eating are unlikely to be false positives. However, only research on attentional bias modification reached acceptable levels of power. These results suggest that CBM interventions may be an effective strategy to enhance the efficacy of weight loss interventions. However, there is room for improvement in the methodological standards of this area of research, especially increasing the statistical power can help to fully clarify the clinical potential of CBM, and determine the role of potential moderators.

A systematic review on neuromodulation therapies for reducing body weight in patients with obesity

The global prevalence of obesity increases yearly along with a rising demand for efficacious, safe, and accessible treatments. Neuromodulation interventions (i.e., deep brain stimulation [DBS], transcranial magnetic stimulation [TMS], transcranial direct current stimulation [tDCS], percutaneous neurostimulation [PENS], vagus nerve stimulation [VNS], and gastric electrical stimulation [GES]) have been proposed as novel therapies. This systematic review sought to examine the safety and efficacy of neuromodulation therapies in reducing body weight in patients with obesity. Using PRISMA guidelines, we performed a systematic review for studies on neuromodulation for the treatment of obesity, resulting in 60 trials included (7 DBS, 5 TMS, 7 tDCS, 17 PENS and VNS, and 24 GES; a total of 3,042 participants). While promising results have been reported in open label studies, double-blinded randomized clinical trials often did not reach their primary endpoints, with no technique inducing a striking reduction in body weight. Bearing in mind the complexity and multifactorial nature of obesity, it is possible that a single treatment may not be enough for patients to lose or maintain the weight lost at long term.

Psychological and metabolic risk factors in older adults with a previous history of eating disorder: A cross-sectional study from the Predimed-Plus study

GOALS

To explore affective and cognitive status, later in life, in individuals with and without previous history of eating disorder (ED), and also its association with higher risk for metabolic syndrome (MetS) symptomatology.

METHODS

A cross-sectional analysis of 6756 adults, aged 55-75 years with overweight/obesity and MetS participating in the Predimed-Plus study was conducted. Participants completed self-reported questionnaires to examine lifetime history of ED, according to DSM-5 criteria, and other psychopathological and neurocognitive factors. Anthropometric and metabolic measurements were also collected.

RESULTS

Of the whole sample, 24 individuals (0.35%) reported a previous history of ED. In this subsample, there were more women and singles compared to their counterparts, but they also presented higher levels of depressive symptoms and higher cognitive impairment, but also higher body mass index (BMI) and severe obesity, than those without lifetime ED.

CONCLUSIONS

This is one of the first studies to analyse the cognitive and metabolic impact of a previous history of ED. The results showed that previous ED was associated with greater affective and cognitive impairment, but also with higher BMI, later in life. No other MetS risk factors were found, after controlling for relevant variables.

Resting-state functional network connectivity underlying eating disorder symptoms in healthy young adults

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This study examined the resting-state functional network connectivity underlying eating disorder symptoms in a large sample of healthy young adults (n = 693).

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Individuals with higher levels of eating disorder symptoms displayed weaker intra-network connectivity of the executive control network and basal ganglia network, as well as weaker inter-network connectivity in the three examined networks (i.e., the executive control network, basal ganglia network, and default mode network).

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The findings suggest that these neural circuits may play a key role in symptoms of disordered eating in healthy adults. They further reveal that the less efficient information exchange within and between intrinsic networks associated with self-referential thinking, inhibitory control, and reward sensitivity are strongly related to eating disorder symptoms.

Previous neuroimaging research of eating disorders such as anorexia nervosa and bulimia nervosa has mainly focused on clinical patients, indicating the crucial role of intrinsic connectivity networks involved in aberrant behavioral control (i.e., executive control network), reward reactivity (i.e., basal ganglia network), and excessive self-focused and body-focused ruminations (i.e., default mode network) in the onset and maintenance of eating disturbances. However, examinations of large-scale resting-state networks that support the role of cognitive control, reward sensitivity, and self-directed thinking in disordered eating have rarely involved non-clinical samples from the general population. This study, involving a total of 693 healthy young adults (68.69% females; mean age, 18.37 years), investigated these issues by using pre-defined functional regions of interest from the executive control network, basal ganglia network, default mode network, and a seed-based region of interest-to-region of interest approach. After statistically controlling for differences in age, sex, body mass index, and head motion, we observed significant associations of higher levels of eating disorder symptoms, especially bulimia-type eating (i.e., binge eating and a combination of binge eating and compensatory behaviors, such as purging via self-induced vomiting or laxative use, and compulsive exercise), with weaker intra-network and inter-network functional synchrony. These results remained significant after excluding underweight, overweight, and obese participants. These findings suggest that these neural circuits may play a key role in the symptoms of disordered eating in healthy adults. They further reveal that the less efficient information exchange within and between intrinsic networks associated with self-referential thinking, inhibitory control, and reward sensitivity are strongly related to eating disorder symptoms.

Cognitive insight is associated with perceived body weight in overweight and obese adults

Background

Accurate perception of body weight is necessary for individuals with a high body mass index (BMI) to initiate strategies to improve their health status. Furthermore, identifying factors that influence accurate body weight perception can assist in designing appropriate educational and weight management programs. We therefore aimed to investigate whether levels of cognitive functioning and insight influence the ability to correctly judge body weight.

Methods

One hundred and eighty four overweight and obese adults who participated in a cross- sectional case-control study and were controls in the aforementioned study were included. The study was conducted in Cape Town, South Africa. Demographic, weight-related, neuropsychiatric, neurocognitive and cognitive insight measures were administered. Regression analysis was conducted to determine the factors associated with correct weight perception.

Results

The final regression model explained 52.3% of variation in accurate perception of body weight and was significant (p ≤ 0. 001). The model correctly classified 79.3% of individuals who were able to correctly and incorrectly judge their weight. Adults with higher BMI, and lower self-certainty, those who reported that they had gained weight in the previous year and those who were told by a healthcare professional to lose or maintain a healthy weight were more likely to correctly judge their weight.

Conclusion

Some aspects of cognitive insight (self-certainty) but not cognitive functioning were associated with perception of body weight in this sample. Awareness of recent weight changes, higher BMI and advice from of health care professionals were also significantly associated with perception of body weight, while demographic variables were not. Understanding the factors that contribute to the correct perception of weight is important in identifying appropriate health interventions that may address the burden of associated non-communicable diseases in overweight and obese individuals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-10559-5.

Executive Functions in Predicting Weight Loss and Obesity Indicators: A Meta-Analysis

While previous studies have suggested that there exists a relationship between obesity and executive function (EF), the mechanisms and causal relationship between them remain unclear. There are important clinical implications of determining whether EF can predict and treat obesity. We conducted a multilevel meta-analysis of randomized controlled trials (RCTs) and longitudinal studies. Specifically, we investigate (a) whether EF interventions have an effect on weight loss, (b) whether baseline EF can be a predictor of future weight loss through obesity intervention, and (c) whether early-life EF can predict future weight loss. Eight RCTs and 17 longitudinal studies with a total of 11,393 participants were identified. We found that (a) EF interventions may not have an effect on weight loss, (b) baseline inhibition (β = 0.259, p = 0.03) and delay discounting (β = −0.17, p = 0.04) significantly predict future weight loss through obesity intervention, (c) age (F = 13.666, p = 0.005) moderates the relationship between working memory and weight loss through intervention, but not weight status, type of intervention, and percentage of female, and (d) early life inhibition (β = 0.185, p = 0.07) is a marginally significant predictor of future weight loss. Our results seem to support the assumption that the relationship between EF and obesity is not direct, and a higher-order factor, such as genes, may link obesity and EF. Building on the preliminary findings, further studies focusing on EF and obesity are needed in the future.

Weight Loss and Improvement of Metabolic Alterations in Overweight and Obese Children Through the I2AO2 Family Program: A Randomized Controlled Clinical Trial

Childhood obesity is a major public health concern. We wanted to evaluate the effectiveness of a multidisciplinary program based on healthy eating, exercise, cognitive-behavioral therapy, and health education to achieve weight loss and improve metabolic parameters in overweight and obese children. A randomized, controlled clinical trial with long-term follow-up (24 months) was conducted at a community care center in overweight and obese individuals aged 6-12 years. A sample of 108 children was divided into an experimental and a control group receiving a standard care program. The experimental groups received a 12-month interdisciplinary program; the results were evaluated at 4 months, the end of the intervention, and at follow-up 12 months later. Anthropometric and biological marker measurements related to metabolic alterations, dyslipidemia (based on total cholesterol), hyperglycemia, fasting glycaemia, triglycerides, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol in blood were recorded. The intervention had a significant effect (p < 0.001) in terms of decreased body mass index, skinfolds, and waist and arm circumferences. These changes were accompanied by biochemical changes underlying an improvement in metabolic parameters, such as a significant reduction in total cholesterol, low-density lipoprotein-cholesterol, triglycerides, and hyperglycemia and a significant increase in high-density lipoprotein-cholesterol. These effects were still significant for markers of excess weight or obesity in the experimental group 12 months after the end of the intervention, suggesting that an enduring change in healthy lifestyles had been maintained period. This interdisciplinary, nurse-led program helped to reduce childhood and adolescent excess weight and obesity and had long-lasting effects.

Targeting automatic processes to reduce unhealthy behaviours: a process framework

While previous frameworks to address health behaviours through targeting underlying automatic processes have stimulated an improved understanding of related interventions, deciding between intervention strategies often remains essentially arbitrary and atheoretical. Making considered decisions has likely been hampered by the lack of a framework that guides the selection of different intervention strategies targeting automatic processes to reduce unhealthy behaviours. We propose a process framework to fulfil this need, building upon the process model of emotion regulation. This framework differentiates types of intervention strategies along the timeline of the unfolding automatic response, distinguishing between three broad classes of intervention strategies - direct antecedent, indirect antecedent, and response-focused. Antecedent-focused strategies aim to prevent the exposure to or activation of automatic responses directly through the avoidance of unwanted stimulus-response associations (i.e., situation modification or situation-specific response selection), or indirectly through automatising self-control (i.e., attentional deployment or cognitive change). Response-focused strategies aim to directly downregulate automatic unwanted responses (i.e., response modulation). Three main working hypotheses derived from this process framework provide practical guidance for selecting interventions, but await direct testing in future studies.

What Should I Eat and Why? The Environmental, Genetic, and Behavioral Determinants of Food Choice: Summary from a Pennington Scientific Symposium

This review details the proceedings of a Pennington Biomedical scientific symposium titled, "What Should I Eat and Why? The Environmental, Genetic, and Behavioral Determinants of Food Choice." The symposium was designed to review the literature about energy homeostasis, particularly related to food choice and feeding behaviors, from psychology to physiology. This review discusses the intrinsic determinants of food choice, including biological mechanisms (genetics), peripheral and central signals, brain correlates, and the potential role of the microbiome. This review also address the extrinsic determinants (environment) of food choice within our physical and social environments. Finally, this review reports the current treatment practices for the clinical management of eating-induced overweight and obesity. An improved understanding of these determinants will inform best practices for the clinical treatment and prevention of obesity. Strategies paired with systemic shifts in our public health policies and changes in our "obesogenic" environment will be most effective at attenuating the obesity epidemic.

Cognition and addiction

In this targeted review, we summarize current knowledge on substance-use disorder (SUD)-related cognitive deficits, the link between these deficits and clinical outcomes, and the cognitive training, remediation, and pharmacological approaches that have the potential to rescue cognition. We conclude that: (i) people with SUDs have moderate deficits in memory, attention, executive functions, and decision-making (including reward expectancy, valuation, and learning); (ii) deficits in higher-order executive functions and decision-making are significant predictors of relapse; (iii) cognitive training programs targeting reward-related appetitive biases, cognitive remediation strategies targeting goal-based decision-making, and pharmacotherapies targeting memory, attention, and impulsivity have potential to rescue SUD-related cognitive deficits. We suggest avenues for future research, including developing brief, clinically oriented harmonized cognitive testing suites to improve individualized prediction of treatment outcomes; computational modeling that can achieve deep phenotyping of cognitive subtypes likely to respond to different interventions; and phenotype-targeted cognitive, pharmacological, and combined interventions. We conclude with a tentative model of neuroscience-informed precision medicine.


Prefrontal Cortex Neuromodulation Enhances Frontal Asymmetry and Reduces Caloric Intake in Patients with Morbid Obesity

OBJECTIVE

The objective of this study was to test the feasibility of a combined intervention involving transcranial direct current stimulation (tDCS) on the dorsolateral prefrontal cortex (dlPFC) and cognitive training (CT). Short-term effects on food consumption, cognition, endocannabinoid (eCB) levels, and electroencephalogram (EEG) markers of future weight loss were explored.

METHODS

Eighteen healthy volunteers with morbid obesity were randomized in a double-blind, placebo-controlled, parallel trial. Participants received sham or active tDCS plus CT for four consecutive days. Cognitive performance, daily food intake, and eCB blood samples were collected before and after the intervention; EEG data were gathered before and after daily training.

RESULTS

The active tDCS + CT group reversed left-dominant frontal asymmetry and increased frontal coherence (FC) in the γ-band (30-45 Hz) after the intervention. The strength of the latter predicted BMI reduction. Additionally, a large intervention effect on food intake was shown in the active tDCS + CT group at follow-up (-339.6 ± 639 kcal on average), and there was a decrease of plasma eCB concentrations.

CONCLUSIONS

dlPFC modulation through tDCS + CT is an effective tool to restore right dominance of the dlPFC and enhance FC in patients with morbid obesity. Moreover, the effect of the strength of FC on BMI suggests that the interhemispheric FC at the dlPFC is functionally relevant for the efficient regulation of food choice.

Cognitive training on eating behaviour and weight loss: A meta-analysis and systematic review

Cognitive deficits play a role in the development and maintenance of overeating and obesity, and cognitive training in obesity refers to a family of interventions aimed at reducing overeating and obesity by improving these cognitive deficits. In this review, we synthesize the current literature on these issues by conducting a meta-analysis of studies investigating the effects of cognitive trainings on eating behaviour and presenting a systematic review of studies investigating the effects of cognitive trainings on weight loss. We examined 66 independent experiments that examined the effects of cognitive training aimed at reducing cognitive bias or improving executive control on eating behaviour and weight loss. Overall, inhibition training, attention bias modification training, and episodic future thinking training significantly influenced eating behaviour; however, approach/avoidance training did not significantly influence eating behaviour. Moderator analyses indicated that the effect of inhibition training on eating behaviour was moderated by training task and food novelty, the effect of approach/avoidance training was moderated by food type, and the effect of episodic future thinking training was moderated by type of episodic future thinking. Literature reviewed on cognitive training and weight loss provided preliminary support for the effects of food-specific inhibition training on weight loss from pre-intervention to post intervention. However, because most of the included studies focused on short-term outcomes in normal-weight samples, longer duration studies in clinical populations (eg, individuals with obesity) are needed to examine the generalizability of these results.

The Executive Functions in Overweight and Obesity: A Systematic Review of Neuropsychological Cross-Sectional and Longitudinal Studies

Background: The increasing incidence of people affected by overweight or obesity is a significant health problem. The knowledge of the factors which influences the inappropriate eating behaviors causing excessive body fat is an essential goal for the research. Overweight and obesity are significant risk factors for many health diseases, such as cardiovascular problems, diabetes. Recently, many studies have focused on the relationship between body weight and cognitive processes. Objectives: This systematic review is aimed to investigate the existence and the nature of the relationship between excessive body weight (overweight/obesity) and executive functions, analyzing cross-sectional, and longitudinal studies in order to verify the evidence of a possible causality between these variables. Methods: The review was carried out according to the PRISMA-Statement, through systematic searches in the scientific databases PubMed, Medline, PsychInfo, and PsycArticles. The studies selected examined performance on executive tasks by participants with overweight or obesity, aged between 5 and 70 years. Studies examining eating disorders or obesity resulting from other medical problems were excluded. Furthermore, the results of studies using a cross-sectional design and those using a longitudinal one were separately investigated. Results: Sixty-three cross-sectional studies and twenty-eight longitudinal studies that met our inclusion and exclusion criteria were analyzed. The results confirmed the presence of a relation between executive functions and overweight/obesity, although the directionality of this relation was not clear; nor did any single executive function emerge as being more involved than others in this relation. Despite this, there was evidence of a reciprocal influence between executive functions and overweight/obesity. Conclusions: This systematic review underlines the presence of a relationship between executive functions and overweight/obesity. Moreover, it seems to suggest a bidirectional trend in this relationship that could be the cause of the failure of interventions for weight reduction. The results of this review highlight the importance of a theoretical model able to consider all the main variables of interest, with the aim to structuring integrated approaches to solve the overweight/obesity problems.

Transcranial Direct Current Stimulation Use in Warfighting: Benefits, Risks, and Future Prospects

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique which provides unique potential to directly improve human capability on a temporary, at needs, basis. The purpose of this paper is to consider the utility of tDCS through analysis of the potential risks and benefits in the context of defence service personnel. First, we look at the potential benefits, focusing primarily on warfighter survivability and enriching cognition quality in support of command and control. Second, we look at the potential detriments to tDCS military use, focusing on adverse effects, safety considerations, and risk. Third, we examine how the level of risk can be mitigated through military doctrine development focusing on safety parameters and exclusion criteria. Finally, we explore the future prospects of military tDCS use, particularly in terms of addressing gaps in the literature so that tDCS can be used ethically and efficaciously at the level of individual personnel.

Novel insights into the spatial and temporal complexity of hypothalamic organization through precision methods allowing nanoscale resolution

The mammalian hypothalamus contains an astounding heterogeneity of neurons to achieve its role in coordinating central responses to virtually any environmental stressor over the life-span of an individual. Therefore, while core features of intrahypothalamic neuronal modalities and wiring patterns are stable during vertebrate evolution, integration of the hypothalamus into hierarchical brain-wide networks evolved to coordinate its output with emotionality, cognition and conscious decision-making. The advent of single-cell technologies represents a recent milestone in the study of hypothalamic organization by allowing the dissection of cellular heterogeneity and establishing causality between opto- and chemogenetic activity modulation of molecularly-resolved neuronal contingents and specific behaviours. Thus, organizational rules to accumulate an unprecedented variety of hierarchical neuroendocrine command networks into a minimal brain volume are being unravelled. Here, we review recent understanding at nanoscale resolution on how neuronal heterogeneity in the mammalian hypothalamus underpins the diversification of hormonal and synaptic output and keeps those sufficiently labile for continuous adaptation to meet environmental demands. Particular emphasis is directed towards the dissection of neuronal circuitry for aggression and food intake. Mechanistic data encompass cell identities, synaptic connectivity within and outside the hypothalamus to link vegetative and conscious levels of innate behaviours, and context- and circadian rhythm-dependent rules of synaptic neurophysiology to distinguish hypothalamic foci that either tune the body's metabolic set-point or specify behaviours. Consequently, novel insights emerge to explain the evolutionary advantages of non-laminar organization for neuroendocrine circuits coincidently using fast neurotransmitters and neuropeptides. These are then accrued into novel therapeutic principles that meet therapeutic criteria for human metabolic diseases.

Current state of the use of neuroimaging techniques to understand and alter appetite control in humans

PURPOSE OF REVIEW

It is in the brain where the decision is made what and how much to eat. In the last decades neuroimaging research has contributed extensively to new knowledge about appetite control by revealing the underlying brain processes. Interestingly, there is the fast growing idea of using these methods to develop new treatments for obesity and eating disorders. In this review, we summarize the findings of the importance of the use of neuropharmacology and neuroimaging techniques in understanding and modifying appetite control.

RECENT FINDINGS

Appetite control is a complex interplay between homeostatic, hedonic, and cognitive processes. Administration of the neuropeptides insulin and oxytocin curb food intake and alter brain responses in reward and cognitive control areas. Additionally, these areas can be targeted for neuromodulation or neurofeedback to reduce food cravings and increase self-control to alter food intake.

SUMMARY

The recent findings reveal the potential of intranasal administration of hormones or modifying appetite control brain networks to reduce food consumption in volunteers with overweight and obesity or individuals with an eating disorder. Although long-term clinical studies are still needed.

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.