Recall of recent lunch and its effect on subsequent snack intake

Exposure to gestational diabetes mellitus in utero impacts hippocampal functional connectivity in response to food cues in children

Objectives

Intrauterine exposure to gestational diabetes mellitus (GDM) increases the risk of obesity in the offspring, but little is known about the underlying neural mechanisms. The hippocampus is crucial for food intake regulation and is vulnerable to the effects of obesity. The purpose of the study was to investigate whether GDM exposure affects hippocampal functional connectivity during exposure to food cues using functional magnetic resonance imaging.

Methods

Participants were 90 children age 7-11 years (53 females) who underwent an fMRI-based visual food cue task in the fasted state. Hippocampal functional connectivity (FC) was examined using generalized psychophysiological interaction in response to high-calorie food versus non-food cues. Food-cue induced hippocampal FC was compared between children with and without GDM exposure, while controlling for possible confounding effects of age, sex and waist-to-hip ratio.

Results

Children with GDM exposure exhibited stronger hippocampal FC to the insula and striatum (i.e., putamen, pallidum and nucleus accumbens) compared to unexposed children, while viewing high caloric food cues.

Conclusions

Intrauterine exposure to GDM was associated with higher food-cue induced hippocampal FC to reward processing regions. Future studies with longitudinal measurements are needed to clarify whether increased hippocampal FC to reward processing regions may raise the risk of the development of metabolic diseases later in life.

Dysfunctional decision-making in binge-eating disorder: A meta-analysis and systematic review

Binge-Eating Disorder (BED) involves anticipatory craving and urges, subjective loss-of-control during binge-eating episodes, and post-feeding psychological distress and guilt. Evidence indicates neurocognitive dysfunctions contribute to BED onset, maintenance, and treatment response. However, an integrated understanding of how cognitive processes underpin BED symptomology is lacking. We utilised a multi-stage decision-making model defining ten cognitive processes underpinning Preference Formation, Choice Implementation, Feedback Processing, and Flexibility/Shifting, to comprehensively review research published since 2013. We used preregistered PICOS criteria to assess 1966 articles identified from PubMed, PsycInfo, and Scopus database searches. This yielded 50 studies reporting behavioural cognitive tasks outcomes, comparing individuals with BED to controls with normal and higher weight. Meta-analyses revealed a unique profile of cognitive dysfunctions that spanned all decision-making stages. Significant deficits were evident in Uncertainty Evaluation, Attentional Inhibition, Choice Consistency, and Cognitive Flexibility/Set-shifting. We propose a novel model of dysfunctional decision-making processes in BED and describe their role in binge-eating behaviour. We further highlight the potential for cognitive interventions to target these processes and address the significant treatment gap in BED.

Imagine this: Visualising a recent meal as bigger reduces subsequent snack intake

Remembering a recent meal reduces subsequent intake of palatable snacks (i.e. the meal-recall effect), however, little is known about the factors which can potentiate this effect. The present experiment investigated whether a stronger meal-recall effect would be observed if recent consumption would be recalled in greater detail, than if it was recalled briefly. Moreover, it was investigated whether imagining a meal as bigger and more satiating than in reality could potentiate the meal-recall effect, and lead to lower intake. It was also explored whether mental visualisation tasks of a recent meal would affect the remembered portion size. Participants (N = 151) ate lunch at the laboratory, and then returned 3 h later to perform the imagination tasks and to participate in a bogus taste test (during which intake was covertly measured). Participants in the two main imagination task groups recalled the lunch meal and then either recalled the consumption episode in great detail or imagined the meal was larger and more filling than in reality. The results showed that imagining a recent meal as larger significantly reduced the quantity of biscuits eaten. However, contrary to the hypotheses, recalling a consumption episode in detail did not decrease snack intake. It was also shown that imagining a recent meal as larger than in reality did not lead participants to overestimate the true size of the meal. In fact, portion size estimations were significantly underestimated in that group. There were no significant estimation differences in any of the other groups. The results of this study suggest that the meal-recall effect can be an effective strategy to reduce food intake and may be amenable to strategic manipulation to enhance efficacy, but seems prone to disruption.

Adults with overweight or obesity use less efficient memory strategies compared to adults with healthy weight on a verbal list learning task modified with food words

Several studies suggest poorer episodic memory among adults with overweight (OW) relative to those with healthy weight (HW); however, few have used food stimuli. To understand the salience of food-related items when assessing memory, we adapted an episodic memory task, by replacing some non-food words with snack foods. Participants were 96 weight-loss seeking adults with OW compared to 48 adults with HW from the community matched on age, gender, ethnicity, and education. Overall memory ability was similar, although a trend showed the adults with HW performed better than adults with OW on immediate recall (d = 0.32, p = 0.07). However, there were clear differences in the use of learning strategies. Adults with HW utilized sematic clustering more effectively than adults with OW during all test phases (ds = 0.44-0.62; ps ≤ 0.01). Adults with HW also utilized serial clustering more effectively (d = 0.51; p < 0.01). Adults with HW showed better semantic clustering for both food and non-food words during immediate and short delay recall (ds = 0.42-0.78; ps ≤ 0.01) but semantic clustering was only better for the non-food category at long delay (d = 0.55; p < 0.01). These results show that adults with OW utilized less efficient learning strategies throughout the task and food-related content may impact learning. Clinically, these findings may suggest that weight-loss treatments should consider incorporating the teaching of learning and memory strategies to help increase utilization of new skills.

Potential mechanisms and modulators of food intake during pregnancy

Dietary choice during pregnancy is crucial not only for fetal development, but also for long-term health outcomes of both mother and child. During pregnancy, dramatic changes in endocrine, cognitive, and reward systems have been shown to take place. Interestingly, in different contexts, many of these mechanisms play a key role in guiding food intake. Here, we review how food intake may be impacted as a function of pregnancy-induced changes across species. We first summarize changes in endocrine and metabolic signaling in the course of pregnancy. Then, we show how these may be related to cognitive function and reward processing in humans. Finally, we link these to potential drivers of change in eating behavior throughout the course of pregnancy.

Do eating behavior traits predict energy intake and body mass index? A systematic review and meta-analysis

At present, it is unclear whether eating behavior traits (EBT) predict objectively measured short-term energy intake (EI) and longer-term energy balance as estimated by body mass index (BMI). This systematic review examined the impact of EBT on BMI and laboratory-based measures of EI in adults ( ≥ 18 years) in any BMI category, excluding self-report measures of EI. Articles were searched up until 28th October 2021 using MEDLINE, PsycINFO, EMBASE and Web of Science. Sixteen EBT were identified and the association between 10 EBT, EI and BMI were assessed using a random-effects meta-analysis. Other EBT outcomes were synthesized qualitatively. Risk of bias was assessed with the mixed methods appraisal tool. A total of 83 studies were included (mean BMI = 25.20 kg/m² , mean age = 27 years and mean sample size = 70). Study quality was rated moderately high overall, with some concerns in sampling strategy and statistical analyses. Susceptibility to hunger (n = 6) and binge eating (n = 7) were the strongest predictors of EI. Disinhibition (n = 8) was the strongest predictor of BMI. Overall, EBT may be useful as phenotypic markers of susceptibility to overconsume or develop obesity (PROSPERO: CRD42021288694).

Orthorexia nervosa, mindful eating, and perfectionism: an exploratory investigation

PURPOSE

Research has drawn associations between Mindful Eating (ME) and perfectionism in the aetiology and treatment of eating disorders (ED), but understanding into the relationship between these factors and Orthorexia nervosa (ON) is limited. The purpose of this research is to explore the relationship between perfectionism, ME, and ON.

METHOD

Participants (n = 670) completed the Düsseldorf Orthorexia scale, the Mindful Eating Behavior scale, and the Big-Three Perfectionism scale Short-form, to reveal the relationship between ON, ME, and perfectionism. The relationship was assessed using correlational and regression analyses.

RESULTS

A positive association was observed between perfectionism and ON. Moreover, perfectionism demonstrated a significant negative correlation with three out of four ME facets, with "eating without distraction" displaying the highest correlation. The "eating with awareness" facet of ME demonstrated a significant relationship with ON, in a negative direction. An unexpected relationship was observed between the focused eating facet of ME and ON, with a positive association being found. A further regression analysis revealed both perfectionism and ME to predict orthorexic tendencies.

CONCLUSION

These findings identify a relationship between ON, ME, and perfectionism. It offers suggestion for the complexity of ME, and how it should be recognised by its different components, estimating a differential predictability and estimation of ON. Further research is required to clarify the direction of causality in the relationships observed, to inform the clinical diagnoses and intervention of ON.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

Functional Relationship between Inhibitory Control, Cognitive Flexibility, Psychomotor Speed and Obesity

In the last decades, it has been proposed that executive functions may be particularly vulnerable to weight-related issues. However, evidence on the matter is mixed, especially when the effects of sociodemographic variables are weighted. Thus, the current study aimed at further examining the relationship between executive functions and obesity. To this aim, we compared treatment-seeking overweight, obese, and morbidly obese patients with normal-weight control participants. We examined general executive functioning (Frontal Assessment Battery−15) and different executive subdomains (e.g., inhibitory control, verbal fluency, and psychomotor speed) in a clinical sample including 208 outpatients with different degrees of BMI (52 overweight, BMI 25−30, M age = 34.38; 76 obese, BMI 30−40, M age = 38.00; 80 morbidly obese, BMI > 40, M age = 36.20). Ninety-six normal-weight subjects served as controls. No difference on executive scores was detected when obese patients were compared with over- or normal-weight subjects. Morbidly obese patients reported lower performance on executive scores than obese, overweight, and normal-weight subjects. Between-group difference emerged also when relevant covariates were taken into account. Our results support the view that morbid obesity is associated with lower executive performance, also considering the critical role exerted by sociodemographic (i.e., sex, age, and education) variables. Our results support the view that executive functioning should be accounted into the management of the obese patient because of non-negligible clinical relevance in diagnostic, therapeutic, and prognostic terms.

Altered neural correlates of episodic memory for food and non-food cues in females with overweight/obesity

Episodic memory formation is fundamental to cognition and plays a key role in eating behaviors, indirectly promoting the maintenance and acceleration of weight gain. Impaired episodic memory function is a hallmark of people with overweight/obesity, nevertheless, little research has been conducted to explore the effects of overweight/obesity on neural networks associated with episodic memory. The current study aimed to unravel the behavioral responses and neurocognitive mechanisms underlying the episodic memory for food and non-food cues in females with overweight/obesity. To explore this issue, a group of females with overweight/obesity (n = 26) and a group of age-matched females with healthy weight (n = 28) participated in a functional magnetic resonance imaging (fMRI) event-related episodic memory paradigm, during which pictures of palatable food and pictures of neutral daily necessities were presented. Whole-brain analyses revealed differential engagement in several neural regions between the groups during an episodic memory task. Specifically, compared to the healthy weight controls, females with overweight/obesity exhibited reduced brain activity in the temporal, parietal, and frontal regions during episodic memory encoding and successful retrieval of both food and non-food cues. Additionally, activation patterns in the left hippocampus and right olfactory cortex of females with and without overweight/obesity suggested that item memory changed according to the type of stimuli presented during item memory. Specifically, females with overweight/obesity showed greater engagement of the left hippocampus and right olfactory cortex when processing food cues, but less activation of the left hippocampus and right olfactory cortex when presented with non-food cues. Consistent with the obesity and suboptimal food-related decision theoretical model, these findings provide evidence of dissociation of the neural underpinnings of episodic memory in females with overweight/obesity and underline important effects of overweight/obesity on brain functions related to episodic memory.

Memory and eating: A bidirectional relationship implicated in obesity

This paper reviews evidence demonstrating a bidirectional relationship between memory and eating in humans and rodents. In humans, amnesia is associated with impaired processing of hunger and satiety cues, disrupted memory of recent meals, and overconsumption. In healthy participants, meal-related memory limits subsequent ingestive behavior and obesity is associated with impaired memory and disturbances in the hippocampus. Evidence from rodents suggests that dorsal hippocampal neural activity contributes to the ability of meal-related memory to control future intake, that endocrine and neuropeptide systems act in the ventral hippocampus to provide cues regarding energy status and regulate learned aspects of eating, and that consumption of hypercaloric diets and obesity disrupt these processes. Collectively, this evidence indicates that diet-induced obesity may be caused and/or maintained, at least in part, by a vicious cycle wherein excess intake disrupts hippocampal functioning, which further increases intake. This perspective may advance our understanding of how the brain controls eating, the neural mechanisms that contribute to eating-related disorders, and identify how to treat diet-induced obesity.

Higher general executive functions predicts lower body mass index by mitigating avoidance behaviors

BACKGROUND

The present study examines the relationship between obesity, executive functions, and body image in a nonclinical population from southern Italy.

METHODS

General executive functioning (Frontal Assessment Battery-15), and body image disturbances (Body Uneasiness Test) were assessed in a sample including 255 participants (138 females, M age = 43.51 years, SD = 17.94, range = 18-86 years; M body mass index (BMI) = 26.21, SD = 4.32, range = 18.03-38.79).

FINDINGS

Multiple Linear Regression Analysis indicated that age, years of education, FAB15 score, body image concerns, and avoidance predicted the variance of BMI. A subsequent mediation analysis highlighted that the indirect effect of FAB15 on BMI through avoidance was statistically significant.

INTERPRETATION

Our results suggest that more performing executive functioning predicts a decrease in BMI that is partially due to the mitigation of avoidance behaviors.

Should you "picture" this? Effects of picture-taking features of food diary apps on memory, liking, and wanting

Picture-taking functions are commonly available features in food diaries and other mobile applications that may influence how we think about the very food we consume. Because memories of food (Higgs & Donohoe, 2011) and the act of recording food consumption (Turk et al., 2013) have been shown to influence desire for and consumption of food, this paper investigated the effects of using the picture-taking feature of a food diary app on liking, wanting, and memory of food. Using a simple food diary app with a picture-taking feature loaded onto iPads, participants took part in a lab experiment where they either did or did not use the picture-taking feature of the app as they ate a snack. To capture the changes in liking and wanting that naturally occur as more food is consumed, participants were also randomly assigned to receive either larger or smaller portions of the snack. The results indicate that picture-taking while eating is associated with greater wanting of the food following consumption. Furthermore, for smaller portions of food, taking pictures during consumption is associated with greater liking of the food. However, taking pictures in the smaller portion size condition was also associated with less detailed recall of food's sensory properties.

Eating behavior as a new frontier in memory research

The study of memory is commonly associated with neuroscience, aging, education, and eyewitness testimony. Here we discuss how eating behavior is also heavily intertwined-and yet considerably understudied in its relation to memory processes. Both are influenced by similar neuroendocrine signals (e.g., leptin and ghrelin) and are dependent on hippocampal functions. While learning processes have long been implicated in influencing eating behavior, recent research has shown how memory of recent eating modulates future consumption. In humans, obesity is associated with impaired memory performance, and in rodents, dietary-induced obesity causes rapid decrements to memory. Lesions to the hippocampus disrupt memory but also induce obesity, highlighting a cyclic relationship between obesity and memory impairment. Enhancing memory of eating has been shown to reduce future eating and yet, little is known about what influences memory of eating or how memory of eating differs from memory for other behaviors. We discuss recent advancements in these areas and highlight fruitful research pursuits afforded by combining the study of memory with the study of eating behavior.

The effect of acute alcohol consumption on meal memory and subsequent food intake: Two laboratory experiments

Altering the quality of episodic meal memories has been shown to affect subsequent food intake. Acute alcohol consumption disrupts memory formation and produces short-term overeating. In two studies, we investigated whether alcohol consumption can affect meal-related memories and later food intake. Study 1 (N = 60, 50% male) investigated how consumption of an alcoholic drink (0.5 g/kg) prior to consumption of a lunch meal affected meal memory of that lunch, and later food intake, compared with a placebo-alcohol. Findings revealed that alcohol consumption did not impair meal memory, and did not affect subsequent food intake. Study 2 (N = 72, 50% male) investigated whether, due to alcohol's retrograde facilitation effect (the enhancement of recall due to reduced interference at the point of exposure) consuming alcohol after consumption of a lunch meal could enhance meal memory, compared with when consumed before a lunch meal (both a dosage of 0.6 g/kg), and compared with consumption of a soft drink. Contrary to prediction, alcohol consumed after a lunch meal did not significantly increase meal memory. But, certain types of meal memory were impaired when alcohol was consumed before the meal, compared with consumption of a soft drink. Subsequent food intake did not differ between conditions. Taken together, findings suggest that alcohol intoxication can impair some forms of meal memory recall, likely due to disruption of memory formation during the encoding phase. However, there was no evidence that this impairment contributes towards alcohol-induced overeating.

Visual, Verbal and Everyday Memory 2 Years After Bariatric Surgery: Poorer Memory Performance at 1-Year Follow-Up

Severe obesity has been associated with reduced performance on tests of verbal memory in bariatric surgery candidates. There is also some evidence that bariatric surgery leads to improved verbal memory, yet these findings need further elucidation. Little is known regarding postoperative memory changes in the visual domain and how patients subjectively experience their everyday memory after surgery. The aim of the current study was to repeat and extend prior findings on postoperative memory by investigating visual, verbal, and self-reported everyday memory following surgery, and to examine whether weight loss and somatic comorbidity predict memory performance. The study was a prospective, observational study in which participants (n = 48) underwent cognitive testing at baseline, 1 and 2 years after bariatric surgery. Repeated measures analyses of variance revealed significantly poorer visual and verbal memory performance at the 1-year follow-up, with performance subsequently returning to baseline levels after 2 years. Verbal learning and self-reported everyday memory did not show significant postoperative changes. Memory performance at 1 year was not significantly predicted by weight loss, changes in C-reactive protein levels or postoperative somatic comorbidity (Type 2 diabetes, sleep apnea, and hypertension). The study demonstrated poorer visual and verbal memory performance at 1-year follow-up that returned to baseline levels after 2 years. These findings are in contrast to most previous studies and require further replication, however, the results indicate that postoperative memory improvements following bariatric surgery are not universal. Findings suggest that treatment providers should also be aware of patients potentially having poorer memory at 1 year following surgery.

Episodic memory for food and non-food cues in females with obesity

Episodic memory is typically thought of as the memory system that makes possible mental time travel through subjective time. This may serve an important function in allowing us to use recent dietary information to predict future food needs and integrate this information with current food availability to adapt motivation accordingly. Growing evidence has suggested that episodic memory influences and is influenced by obesity. However, there is limited available evidence on the characteristics of episodic memory for food and non-food cues in people with obesity. The present study attempts to address this association and apply an episodic memory task to evaluate item memory and source memory for food and non-food cues in females with obesity. Participants were 26 females with obesity and 30 females with healthy weight, who were undergraduate students aged 17-24 years. They completed the Dutch Eating Behavior Questionnaire, hunger visual analog scale, fullness visual analog scale, desire-to-eat visual analog scale, and an episodic memory task including item memory and source memory. Results showed that the episodic memory patterns of females with and without obesity changed according to the type of stimuli. Specifically, females with obesity outperformed females with healthy weight in item memory for food cues, but showed deficits in item memory for non-food cues and source memory for both food and non-food cues. Taken together, based on the obesity and suboptimal food-related decision theoretical model, these findings are of great theoretical and clinical significance to explore episodic memory pattern differences between people with and without obesity.

Using Smartphones When Eating Increases Caloric Intake in Young People: An Overview of the Literature

Recent literature highlights that the use of smartphones during meals increases the number of calories ingested in young people. Although the distraction interferes with physiological signals of hunger and satiety, a social facilitation effect has also been suggested. Cognition is a pivotal component in regulating food intake, and activities requiring high perceptual demands should be discouraged during meals.

The role of memory ability, depth and mode of recall in the impact of memory on later consumption

It has been shown that recalling a meal eaten a few hours earlier (vs. the previous day) leads to reduced snacking ('meal-recall' effect). This study attempted to replicate this effect, by assessing participants' (N = 77, mean age = 33.30 [SD = 14.98], mean BMI = 23.77 [SD = 3.72], 74% female) biscuit consumption during a bogus taste test in two separate sessions, before which participants recalled a recent or a distant meal. It was explored whether factors that might affect the quality of a meal-memory, particularly individual differences in memory ability and depth of recall, would influence the meal-recall effect. To this end, only participants with a low or high memory ability were recruited for the study and were allocated to either an unguided-recall or guided-recall condition. In the unguided condition, participants were asked to recall what they ate, and in the guided condition they were prompted for further details regarding their meal. Participants were asked to either recall their meal out loud through an interview with the experimenter or by writing their recollection down on the computer. Contrary to the initial hypotheses, it was found that only the written group demonstrated the meal-recall effect, whereas the verbal group did not. Moreover, this was specific to the written, unguided group, in which participants ate about 9 g fewer biscuits after recalling a recent (vs. a distant) meal, F (1,15) = 6.07, p = .026, η_p² = 0.288. The written, guided group's snacking seemed to increase by about 8 g after recalling a recent (vs. a distant) meal, F (1,20) = 7.31, p = .014, η_p² = 0.268. The meal-recall effect was not evident in the verbal group. Memory ability did not influence the magnitude of the meal-recall effect. The results highlight the importance of contextual factors in modulating the meal-recall effect.

Cognitive Distraction at Mealtime Decreases Amount Consumed in Healthy Young Adults: A Randomized Crossover Exploratory Study

BACKGROUND

Environmental distractions have been shown to affect eating patterns.

OBJECTIVE

The purpose of this study was to determine the effects of a cognitive distraction on amount, preference, and memory of food consumed and perceptions of fullness, hunger, and enjoyment of food in a healthy young-adult population.

METHODS

A randomized controlled crossover study of 119 healthy adults (20.2 ± 1.4 y; 57% women; 48% white) assigned participants to begin under either the distracted (DIS, n = 55) or control (CON, n = 64) conditions. DIS participants consumed a meal of quiche while completing a Rapid Visual Information Processing (RVIP) for 15 min. CON participants ate without any task assignment. After a 30-min rest period, participants were offered a snack and given 5 min to eat ad libitum. Participants completed a survey assessing fullness, hunger, and enjoyment of the meal using 100 mm visual analogue scales. One week later, participants completed the opposite condition. Data were analyzed using ANOVA.

RESULTS

Those in DIS consumed 13 g less of the meal (P < 0.001), even when comparing by initial condition (P < 0.001) and adjusting for sex (P < 0.001). A carryover effect of initial condition was found (P < 0.001), such that participants first assigned to DIS condition consumed less (95.2 ± 61.7 g) when distracted compared to all other condition combinations (127-133 g). Those in DIS had decreased accuracy for both memory of quiche received (absolute difference, 1.1 ± 1.6 compared with 0.7 ± 1.2 for CON, P < 0.001) and memory of quiche consumed (0.8 ± 1.1 for DIS compared with 0.7 ± 1.2 for CON, P = 0.007).

CONCLUSIONS

When distracted, healthy young adults consumed significantly less food and their memory of the meal was dampened. These findings underscore the potential importance of cognitive distraction in affecting food intake. This trial was registered at clinicaltrials.gov as NCT04078607.

A smartphone based attentive eating intervention for energy intake and weight loss: results from a randomised controlled trial

BACKGROUND

Laboratory studies suggest that eating more 'attentively' (e.g. attending to food being eaten and recalling eating episodes) can reduce food intake among participants with both healthy weight and overweight. The aim of this trial was to assess whether a smartphone application that encourages a more attentive eating style reduces energy intake and promotes weight loss.

METHODS

In an open-label, single centre, parallel groups, individually randomised controlled trial, 107 adults with overweight/obesity in Merseyside, UK used an attentive eating smartphone application along with standard dietary advice (intervention group) or standard dietary advice only (control group) for 8 weeks. The primary outcomes were change in body weight at 8 weeks and energy intake at 4 and 8 weeks. Additional outcomes included self-reported eating behaviours measured at 8 weeks. Differences between groups were assessed with linear regression (adjusted) using multiple imputation for missing data. Study protocol registered prospectively at ( https://doi.org/10.17605/osf.io/btzhw ).

RESULTS

There was no significant difference between the intervention and control group in weight lost at 8 weeks, or change in self-reported 24 h or objective taste-test energy intake at 4 or 8 weeks. Mean weight loss in the intervention group (n = 53) was 1.2 kg and 1.1 kg in the control group (n = 54), adjusted difference of - 0.10 (- 1.6 to 1.3) kg. Self-reported eating behaviours at 8 weeks also did not differ across groups. The intervention was largely used as intended and a per protocol analysis confined to participants in the intervention group that used the attentive eating smartphone application regularly and as intended also showed no effect on energy intake or weight loss.

CONCLUSIONS

A smartphone based attentive eating intervention and standard dietary advice did not result in reduced energy intake or greater weight loss at 4 or 8 week follow-up than standard dietary advice alone.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03602001 . Registered retrospectively on 26th July 2018. Prospectively registered on the Open Science Framework on 11th August 2017.

Real-time fMRI neurofeedback training to improve eating behavior by self-regulation of the dorsolateral prefrontal cortex: A randomized controlled trial in overweight and obese subjects

Obesity is associated with altered responses to food stimuli in prefrontal brain networks that mediate inhibitory control of ingestive behavior. In particular, activity of the dorsolateral prefrontal cortex (dlPFC) is reduced in obese compared to normal-weight subjects and has been linked to the success of weight-loss dietary interventions. In a randomized controlled trial in overweight/obese subjects, we investigated the effect on eating behavior of volitional up-regulation of dlPFC activity via real-time functional magnetic resonance imaging (fMRI) neurofeedback training. Thirty-eight overweight or obese subjects (BMI 25-40 kg/m²) took part in fMRI neurofeedback training with the aim of increasing activity of the left dlPFC (dlPFC group; n = 17) or of the visual cortex (VC/control group; n = 21). Participants were blinded to group assignment. The training session took place on a single day and included three training runs of six trials of up-regulation and passive viewing. Food appraisal and snack intake were assessed at screening, after training, and in a follow-up session four weeks later. Participants of both groups succeeded in up-regulating activity of the targeted brain area. However, participants of the control group also showed increased left dlPFC activity during up-regulation. Functional connectivity between dlPFC and ventromedial PFC, an area that processes food value, was generally increased during up-regulation compared to passive viewing. At follow-up compared to baseline, both groups rated pictures of high-, but not low-calorie foods as less palatable and chose them less frequently. Actual snack intake remained unchanged but palatability and choice ratings for chocolate cookies decreased after training. We demonstrate that one session of fMRI neurofeedback training enables individuals with increased body weight to up-regulate activity of the left dlPFC. Behavioral effects were observed in both groups, which might have been due to dlPFC co-activation in the control group and, in addition, unspecific training effects. Improved dlPFC-vmPFC functional connectivity furthermore suggested enhanced food intake-related control mechanisms. Neurofeedback training might support therapeutic strategies aiming at improved self-control in obesity, although the respective contributions of area-specific mechanisms and general regulation effects are in need of further investigation.

Episodic memory as an explanation for the insurance hypothesis in obesity

In evaluating the insurance hypothesis as an explanation for obesity, we propose one missing piece of the puzzle. Our suggested explanation for why individuals report food insecurity is that an individual may have an impaired episodic ability to plan for the future.

The Cognitive Control of Eating and Body Weight: It's More Than What You "Think"

Over the past decade, a great deal of research has established the importance of cognitive processes in the control of energy intake and body weight. The present paper begins by identifying several of these cognitive processes. We then summarize evidence from human and nonhuman animal models, which shows how excess intake of obesity-promoting Western diet (WD) may have deleterious effects on these cognitive control processes. Findings that these effects may be manifested as early-life deficits in cognitive functioning and may also be associated with the emergence of serious late-life cognitive impairment are described. Consistent with these possibilities, we review evidence, obtained primarily from rodent models, that consuming a WD is associated with the emergence of pathophysiologies in the hippocampus, an important brain substrate for learning, memory, and cognition. The implications of this research for mechanism are discussed within the context of a “vicious-cycle model,” which describes how eating a WD could impair hippocampal function, producing cognitive deficits that promote increased WD intake and body weight gain, which could contribute to further hippocampal dysfunction, cognitive decline, and excess eating and weight gain.

What is the role of episodic foresight in planning for future needs? Theory and two experiments

Considerable evidence suggests that episodic memory and foresight rely on the same underlying cognitive processes. Some theorists have suggested that the key role of episodic foresight is to allow an individual to disengage from current states to plan for future needs. However, the contribution of episodic cognition to this type of planning has not been investigated. We present two experiments exploring future-state planning in 3-6-year-old children and healthy young adults, finding that both groups were consistently biased towards current states. We further found that there were few relationships between episodic memory ability and future-state planning. Where there was a relationship, the degree of bias was positively related to episodic memory ability, such that those with better episodic were more biased by their current motivational state. These findings are consistent with previous research suggesting that episodic cognition is particularly vulnerable to bias from current feelings. We propose an account in which episodic cognition allows for cross-talk between current and future motivational states, and that while this can aid prospective decision-making in some scenarios, it may hinder it in others.

Effects of blood glucose on delay discounting, food intake and counterregulation in lean and obese men

BACKGROUND

Delay discounting as a measure of impulsivity has been shown to be higher in obesity with an association of increased food intake. Moreover, obese humans showed a higher wanting for high-calorie food than lean men when blood glucose concentrations were low. First studies linking blood glucose levels to delay discounting yielded mixed results. We hypothesized that obese people - in comparison to lean men - have a relative lack of energy, especially when blood glucose levels are low, that results in higher levels of delay discounting, food intake and hormonal counterregulation.

METHODS

We investigated 20 lean and 20 obese healthy young men in a single-blind balanced cross-over design. With a standardized glucose clamp technique, subjects underwent a hypoglycemic state in one condition and a euglycemic state in the control condition. Regularly, blood was sampled for assessment of hormonal status, and questionnaires were filled out to assess delay discounting and symptom awareness. After normalizing blood glucose concentrations, subjects were free to eat from a standardized test buffet, followed by a snack test.

RESULTS

Delay discounting was higher in obese than in lean men throughout experiments (p < 0.03). However, we did not observe significant discounting differences between glucose conditions (p > 0.1). Furthermore, the discounting performance did not correlate with food intake from the test buffet or snack test (p > 0.3). As a response to hypoglycemia, hormonal counterregulation was pronounced in both weight groups (p < 0.03), but responses of ACTH, norepinephrine and glucagon were stronger in obese compared to lean men (p < 0.03). Also, intake from the high-calorie buffet after hypoglycemia compared to euglycemia was higher in obese subjects (p < 0.02) but comparable in lean men (p > 0.5).

CONCLUSIONS

Our data suggest that augmented delay discounting is a robust feature in obesity that is not linked to glucose levels or actual food intake. With our systematically controlled approach, combining performance in delay discounting with regard to distinct blood glucose levels, different weight groups, counterregulatory behavior and food intake, our results imply that delay discounting is not susceptible to fluctuations of blood glucose and do not support the assumption that a low body's energy content leads to increased impulsivity. Further replications including women and larger sample sizes are needed to corroborate our data.

Cognitive Control of Eating: the Role of Memory in Appetite and Weight Gain

PURPOSE OF REVIEW

The present review organises the recent literature on the role of memory in eating behaviours and provides an overview of the current evidence relating to the associations between memory and weight gain.

RECENT FINDINGS

Research over the last few years has highlighted working memory as an important cognitive process that underpins many aspects of appetite control. Recent work on episodic memory and appetite has replicated work showing that manipulating memory for recent eating affects later consumption and extended this work to examine associations between individual differences in memory and eating behaviours. Poorer episodic memory ability is related to a reduced sensitivity to internal states of hunger and satiety and a tendency towards uncontrolled eating. There is also recent evidence to suggest that working memory and episodic memory impairments are related to weight gain and high BMI. Working memory and episodic memory are core cognitive processes that are critical for food-related decision-making, and disruption to these processes contributes to problems with appetite control and weight gain, which suggests that weight loss programmes might be improved by the addition of cognitive training.

Oxytocin curbs calorie intake via food-specific increases in the activity of brain areas that process reward and establish cognitive control

The hypothalamic neurohormone oxytocin decreases food intake via largely unexplored mechanisms. We investigated the central nervous mediation of oxytocin's hypophagic effect in comparison to its impact on the processing of generalized rewards. Fifteen fasted normal-weight, young men received intranasal oxytocin (24 IU) or placebo before functional magnetic resonance imaging (fMRI) measurements of brain activity during exposure to food stimuli and a monetary incentive delay task (MID). Subsequently, ad-libitum breakfast intake was assessed. Oxytocin compared to placebo increased activity in the ventromedial prefrontal cortex, supplementary motor area, anterior cingulate, and ventrolateral prefrontal cortices in response to high- vs. low-calorie food images in the fasted state, and reduced calorie intake by 12%. During anticipation of monetary rewards, oxytocin compared to placebo augmented striatal, orbitofrontal and insular activity without altering MID performance. We conclude that during the anticipation of generalized rewards, oxytocin stimulates dopaminergic reward-processing circuits. In contrast, oxytocin restrains food intake by enhancing the activity of brain regions that exert cognitive control, while concomitantly increasing the activity of structures that process food reward value. This pattern points towards a specific role of oxytocin in the regulation of eating behaviour in humans that might be of relevance for potential clinical applications.

Interactions between metabolic, reward and cognitive processes in appetite control: Implications for novel weight management therapies

Traditional models of appetite control have emphasised the role of parallel homeostatic and hedonic systems, but more recently the distinction between independent homeostatic and hedonic systems has been abandoned in favour of a framework that emphasises the cross talk between the neurochemical substrates of the two systems. In addition, evidence has emerged more recently, that higher level cognitive functions such as learning, memory and attention play an important role in everyday appetite control and that homeostatic signals also play a role in cognition. Here, we review this evidence and present a comprehensive model of the control of appetite that integrates cognitive, homeostatic and reward mechanisms. We discuss the implications of this model for understanding the factors that may contribute to disordered patterns of eating and suggest opportunities for developing more effective treatment approaches for eating disorders and weight management.

Binge-eating disorder may be distinguished by visuospatial memory deficits

OBJECTIVE

Binge eating disorder (BED), characterized by recurrent episodes of loss of control overeating, is highly comorbid with overweight and obesity. Both loss of control eating and higher body mass index have been associated with poor memory. The current study sought to clarify the relationships between BED, weight and memory. Specifically, visual memory was examined, given evidence of impaired visuospatial abilities in overweight individuals and little research on visual memory in BED.

METHOD

Overweight and normal-weight women with BED and matched healthy controls were administered the Rey Complex Figure Test.

RESULTS

Planned contrasts revealed that normal-weight healthy controls performed better than all other groups on the immediate and delayed recall portions of the task. Performance on the immediate recall portion was better among normal-weight individuals than overweight individuals, and performance on both the immediate and delayed recall portions was better among individuals without BED than those with BED. No differences between groups were seen on the copy or recognition trials.

CONCLUSIONS

Visual memory appears to be impaired among overweight participants and both normal and overweight participants with BED. This finding was specific to retrieval. Replication of this finding in BED using different measures of memory is needed.

Additive effects of sensory-enhanced satiety and memory for recent eating on appetite

The sensory characteristics of a product have been shown to interact with actual nutrient content to generate satiety. Separately, cued recall of recent eating has also been shown to reduce food intake. Here we explore for the first time how these two effects interact, with the hypothesis that sensory enhancement of satiety might be mediated by more vivid memory of the earlier consumed item. On each of two test sessions, 119 women volunteers consumed a control drink (lemonade) on one morning and then one of two test drinks on the next day 30 min before an ad libitum lunch. The test drinks were equicaloric but one was noticeably thicker and creamier, and expected to generate stronger satiety. Just prior to the test lunch, participants were asked to recall either the test drink (test recall) or the drink from the previous day (control recall). Overall, lunch intake was significantly lower after the thicker and creamier (enhanced sensory ES) than thinner (low sensory: LS) test drink (p < 0.001, η² = 0.11) regardless of recall condition (p = 0.65, η² < 0.01), but was significantly lower after the test than control recall condition (p < 0.001, η² = 0.14). Rated hunger was lower after consuming the ES than LS drink both immediately after consumption (p < 0.001, η² = 0.11) and prior to the test lunch (p = 0.007, η² = 0.06), while rated hunger just before lunch tended to be lower after recalling the test than control drink (p = 0.052, η² = 0.03) regardless of the sensory characteristics (p = 0.27, η² = 0.01). Overall these data further demonstrate the power of 'sensory-enhanced satiety' and cued recall of earlier eating as methods to reduce acute food intake, but suggest these effects operate independently.

Adverse effects of consuming high fat–sugar diets on cognition: implications for understanding obesity

There is increasing evidence for important roles of key cognitive processes, including attention, memory and learning, in the short-term decision making about eating. There is parallel evidence that people who are overweight or obese tend to perform worse on a variety of cognitive tasks. In this review, the evidence for these two ideas is summarised and then the idea that overconsumption of Western-style high-fat (HF)–high-sugar diets may underlie the association between obesity and poorer cognitive performance is explored. In particular, evidence in animals and human subjects that repeated consumption of HF or HF and sugar (HFS) diets leads to specific impairments in the functioning of the hippocampus, which underpin the consequent changes in cognition is summarised. These findings lead into the vicious cycle model (VCM), which suggests that these cognitive changes have knock-on negative effects for future appetite control, and evidence that altered hippocampal function is also associated with impaired appetite control is explored. The review concludes that there is consistent evidence in the animal literature and emerging evidence from human studies that supports this VCM. It is also noted, however, that to date studies lack the nutritional specificity needed to be able to translate these basic research findings into clear nutritional effects, and concludes that there is an urgent need for additional research to clarify the precise nature of the apparent effects of consuming HFS diets on cognition.

The bogus taste test: Validity as a measure of laboratory food intake

Because overconsumption of food contributes to ill health, understanding what affects how much people eat is of importance. The ‘bogus’ taste test is a measure widely used in eating behaviour research to identify factors that may have a causal effect on food intake. However, there has been no examination of the validity of the bogus taste test as a measure of food intake. We conducted a participant level analysis of 31 published laboratory studies that used the taste test to measure food intake. We assessed whether the taste test was sensitive to experimental manipulations hypothesized to increase or decrease food intake. We examined construct validity by testing whether participant sex, hunger and liking of taste test food were associated with the amount of food consumed in the taste test. In addition, we also examined whether BMI (body mass index), trait measures of dietary restraint and over-eating in response to palatable food cues were associated with food consumption. Results indicated that the taste test was sensitive to experimental manipulations hypothesized to increase or decrease food intake. Factors that were reliably associated with increased consumption during the taste test were being male, have a higher baseline hunger, liking of the taste test food and a greater tendency to overeat in response to palatable food cues, whereas trait dietary restraint and BMI were not. These results indicate that the bogus taste test is likely to be a valid measure of food intake and can be used to identify factors that have a causal effect on food intake.

Volitional regulation of brain responses to food stimuli in overweight and obese subjects: A real-time fMRI feedback study

Obese subjects who achieve weight loss show increased functional connectivity between dorsolateral prefrontal cortex (dlPFC) and ventromedial prefrontal cortex (vmPFC), key areas of executive control and reward processing. We investigated the potential of real-time functional magnetic resonance imaging (rt-fMRI) neurofeedback training to achieve healthier food choices by enhancing self-control of the interplay between these brain areas. We trained eight male individuals with overweight or obesity (age: 31.8 ± 4.4 years, BMI: 29.4 ± 1.4 kg/m²) to up-regulate functional connectivity between the dlPFC and the vmPFC by means of a four-day rt-fMRI neurofeedback protocol including, on each day, three training runs comprised of six up-regulation and six passive viewing trials. During the up-regulation runs of the four training days, participants successfully learned to increase functional connectivity between dlPFC and vmPFC. In addition, a trend towards less high-calorie food choices emerged from before to after training, which however was associated with a trend towards increased covertly assessed snack intake. Findings of this proof-of-concept study indicate that overweight and obese participants can increase functional connectivity between brain areas that orchestrate the top-down control of appetite for high-calorie foods. Neurofeedback training might therefore be a useful tool in achieving and maintaining weight loss.

Oxytocin's inhibitory effect on food intake is stronger in obese than normal-weight men

Background/Objectives:

Animal studies and pilot experiments in men indicate that the hypothalamic neuropeptide oxytocin limits food intake, and raise the question of its potential to improve metabolic control in obesity.

Subjects/Methods:

We compared the effect of central nervous oxytocin administration (24 IU) via the intranasal route on ingestive behaviour and metabolic function in 18 young obese men with the results in a group of 20 normal-weight men. In double-blind, placebo-controlled experiments, ad libitum food intake from a test buffet was examined in fasted subjects 45 min after oxytocin administration, followed by the assessment of postprandial, reward-driven snack intake. Energy expenditure was repeatedly assessed by indirect calorimetry and blood was sampled to determine concentrations of blood glucose and hormones.

Results:

Oxytocin markedly reduced hunger-driven food intake in the fasted state in obese but not in normal-weight men, and led to a reduction in snack consumption in both groups, whereas energy expenditure remained generally unaffected. Hypothalamic–pituitary–adrenal axis secretion and the postprandial rise in plasma glucose were blunted by oxytocin in both groups.

Conclusions:

Oxytocin exerts an acutely inhibitory impact on food intake that is enhanced rather than decreased in obese compared with normal-weight men. This pattern puts it in contrast to other metabolically active neuropeptides and bodes well for clinical applications of oxytocin in the treatment of metabolic disorders.

Higher body mass index is associated with episodic memory deficits in young adults

Obesity has become an international health crisis. There is accumulating evidence that excess bodyweight is associated with changes to the structure and function of the brain and with a number of cognitive deficits. In particular, research suggests that obesity is associated with hippocampal and frontal lobe dysfunction, which would be predicted to impact memory. However, evidence for such memory impairment is currently limited. We hypothesised that higher body mass index (BMI) would be associated with reduced performance on a test of episodic memory that assesses not only content, but also context and feature integration. A total of 50 participants aged 18–35 years, with BMIs ranging from 18 to 51, were tested on a novel what–where–when style episodic memory test: the “Treasure-Hunt Task”. This test requires recollection of object, location, and temporal order information within the same paradigm, as well as testing the ability to integrate these features into a single event recollection. Higher BMI was associated with significantly lower performance on the what–where–when (WWW) memory task and all individual elements: object identification, location memory, and temporal order memory. After controlling for age, sex, and years in education, the effect of BMI on the individual what, where, and when tasks remained, while the WWW dropped below significance. This finding of episodic memory deficits in obesity is of concern given the emerging evidence for a role for episodic cognition in appetite regulation.

Cognitive processing of food rewards

Cues associated with tasty foods, such as their smell or taste, are strong motivators of eating, but the power of food cues on behaviour varies from moment to moment and from person to person. Variation in the rewarding value of a food with metabolic state explains why food cues are more attractive when hungry. However, cognitive processes are also important determinants of our responses to food cues. An urge to consume a tempting food may be resisted if, for example, a person has a longer term goal of weight loss. There is also evidence that responses to food cues can be facilitated or inhibited by memory processes. The aim of this review is to add to the literature on cognitive control of eating by reviewing recent evidence on the influence of working memory and episodic memory processes on responses to food cues. It is argued that processing of food information in working memory affects how much attention is paid to food cues in the environment and promotes the motivation to seek out food in the absence of direct contact with food cues. It is further argued that memories of specific recent eating episodes play an important role in directing food choices and influencing when and how much we eat. However, these memory processes are prone to disruption. When this happens, eating behaviour may become more cue-driven and less flexible. In the modern food environment, disruption of cognitive processing of food reward cues may lead to overconsumption and obesity.

Human diet and cognition

Cognition influences what, when and how much we eat, which in turn affects the brain and hence cognition. In this overview, focusing mainly on the human literature, we start by examining cognitive influences on food and eating. This includes food preferences and choices (e.g., effects of learning, advertising, and cultural taboos), food habits relating to when and how much to eat (e.g., the concept of meals, dieting, and hunger strikes), the perception of food (e.g., the influence of appearance, food labels, and conceptions of naturalness), and how food perception is influenced by expertise. We also review how these various influences are disrupted by abnormalities of cognition (e.g., Gourmand syndrome, amnesia, and anorexia nervosa). The second part of the overview focuses on how diet affects cognition. We start by looking at the acute effects of diet, notably the impact of breakfast on cognitive performance in children. This is followed by a review of the effects of extended dietary exposures-years and lifetimes of particular diets. Here we look at the impacts of protein-energy malnourishment and Western-style diets, and their different, but adverse affects on cognition, and the beneficial effects on cognition of breast-feeding and certain dietary practices. We then outline how diet and cooking may have allowed the evolution of the large energy-hungry human brain. This overview serves to illustrate the multiple interactions that exist between cognition and diet, their importance to health and disease, and their impact on thinking about the role of conscious processes in decision making. WIREs Cogn Sci 2014, 5:463-475. doi: 10.1002/wcs.1290 For further resources related to this article, please visit the WIREs website.

CONFLICT OF INTEREST

The authors have declared no conflicts of interest for this article.