Body weight status, eating behavior, sensitivity to reward/punishment, and gender: relationships and interdependencies

Association between Diet Quality and Eating Behavior in Type 2 Diabetes Adults: A Cross-Sectional Study

Type 2 diabetes mellitus (T2DM) has become a global epidemic. To effectively control T2DM, individuals must adhere to a high-quality diet that encompasses not only healthy dietary patterns but also promotes positive eating behaviors. We conducted a cross-sectional study on 314 patients with T2DM, and we evaluated the diet quality and also examined the associations between eating behavior, diet quality, and anthropometric and clinical factors in T2DM patients. We used the Diet Quality Index-International and Dutch Eating Behavior Questionnaire to assess dietary characteristics. We found that women had a significantly higher diet quality than men (61.40 vs. 58.68, p = 0.002) but were also more prone to emotional eating (2.00 vs. 1.53, p < 0.001) and restrained eating (2.39 vs. 2.05, p = 0.002). Restrained eating correlated with duration of diabetes (r = -0.169, p = 0.003), body mass index (r = 0.182, p = 0.001), and external eating with glycated hemoglobin (r = 0.114, p = 0.044). Patients with emotional eating had a higher vitamin C adequacy score (β = 0.117, p = 0.045). External eating was positively associated with grain adequacy (β = 0.208, p < 0.001) and negatively associated with empty-calorie food moderation score (β = -0.125, p = 0.032). For restrained eating, we found associations with vitamin C adequacy (β = -0.138, p = 0.017) and fruit adequacy (β = 0.125, p = 0.033). In conclusion, the results of this study provide valuable insight into dietary behavior and emphasize the importance of promoting healthy eating habits for T2DM patients.

Motivational and self-regulatory processes associated with weight-related parenting behaviors

Background

Parents play an influential role on their child's eating and physical activity. How maternal personality and individual differences, such as motivation and self-regulation, are associated with their weight-related parenting has yet to be studied. The current study examined relationships of mothers' motivational and self-regulatory characteristics with weight-related parenting practices.

Methods

Mothers (N = 149, MAge = 42.78 years, 49% Hispanic/Latino) of school-aged children (ages 10-14 years, 55.7% female) completed questionnaires assessing behavioral inhibition system/behavioral activation system (BIS/BAS), self-control, and weight-related parenting practices (i.e., role modeling, food restriction, rule enforcement, limiting, discipline, pressure to eat). Structural equation modeling examined associations of BIS, BAS, and self-control with parenting practices.

Results

Among mothers, higher avoidance motivation was associated with difficulty with rule enforcement. Higher approach motivation was associated with less limiting of unhealthy food and sedentary behavior. Higher self-control predicted more role modeling and less difficulty with rule enforcement.

Conclusion

Findings support associations of maternal motivational and self-regulatory processes with weight-related parenting behaviors. Results may inform tailored strategies based on individual differences for family-based interventions for parenting.

Time estimation and passage of time judgment predict eating behaviors during COVID-19 lockdown

Poor eating habits often lead to health concerns. While mental health conditions such as stress and anxiety have been linked as predictors for eating behaviors, cognitive factors may also contribute to eating practices during the early stages of the mandatory COVID-19 lockdown. In the current study, participants responded to a survey that asked them to judge the passing of time (PoTJ) and to produce short intervals (via a time production task) as an index of the internal clock speed. Additionally, they responded to questions about snacking frequency and the tendency to overeat during lockdown. We observed that those who judged time to pass slowly also reported a greater tendency to snack and overeat during the pandemic. Additional analysis also revealed that the effect of PoTJ on snacking is moderated by the internal clock speed such that those who felt time was passing by slowly, and in combination with a faster internal clock (as indexed by shorter duration production), had a greater tendency to snack. The results suggest that different aspects of temporal cognition play potential roles in influencing different types of eating behaviors. Our findings therefore have implications for eating disorders, along with the potential of time-based intervention or behavioral modification approaches.

The reward and punishment responsivity and motivation questionnaire (RPRM-Q): A stimulus-independent self-report measure of reward and punishment sensitivity that differentiates between responsivity and motivation

Reward and punishment sensitivity seem important traits in understanding behavior in general and psychopathology in particular. Though the definitions used for reward and punishment sensitivity differentiate between responsivity and motivation, the measures thus far used to assess these constructs do not. Further, specificity of the type of reward (e.g., drugs) and punishment (e.g., spiders) in questionnaires might result in measurement bias especially when examining the relationship with psychopathology. Therefore, we developed a stimulus-independent multidimensional questionnaire of reward and punishment sensitivity that differentiates between responsivity and motivation. This study addresses the psychometric qualities of this newly developed reward and punishment responsivity and motivation questionnaire (RPRM-Q). On the basis of exploratory ordinal factor analysis (N = 273) that was used to examine the quality of the initial pool of 39 items, the number of items was reduced to 18. Confirmatory ordinal factor analysis on the remaining items in an independent sample (N = 328) supported a 18-item four-factor model, and showed acceptable to good internal reliability. The relationship between the subscales of the RPRM-Q and often used questionnaires was examined in the combined sample (N = 601), which showed some first support for the ability of the new questionnaire to differentiate between responsivity and motivation to approach/avoid. The findings indicate that the RPRM-Q might be a helpful instrument to further test the relevance of punishment and reward sensitivity in psychopathology.

Reward sensitivity, eating behavior, and obesity-related outcomes: A systematic review

INTRODUCTION

Previous research has identified reward sensitivity as an important factor that may contribute to the engagement in eating behavior (e.g., binge eating, emotional eating, etc.) and increase obesity risk. In the current study, we conducted a systematic review of the literature to determine the relationships between reward sensitivity, eating behavior, and obesity-related outcomes. The study focused on two commonly used measures of reward sensitivity in the literature: the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ) and the Behavioral Inhibition Scale/Behavioral Activation Scale (BIS/BAS Scale).

METHOD

We conducted a systematic search to identify studies that analyzed reward sensitivity as a predictor of eating behavior or obesity-related outcomes, and measured reward sensitivity using the SPSRQ or BIS/BAS Scale. The search yielded N=19 total publications included in the review.

RESULTS

Findings indicated that reward sensitivity, primarily measured by summary scores on the SPSRQ or BIS/BAS Scale, were positively associated with a variety of eating behaviors and obesity-related outcomes with small to moderate effect sizes. Findings were most consistent across studies that examined the association between reward sensitivity and eating behavior outcomes (e.g., binge eating, emotional eating) (r values= .08 to .41; p values < .001 to p < .05) and food consumption outcomes (e.g., palatable food intake) (r values = .21 to .40; p < .001 to p values < .05). Findings were less consistent for food craving and BMI outcomes, and revealed these relationships may depend on individual-level factors and/or environment-related factors, (e.g., food cues). A quality evaluation using the Critical Appraisal Tool for Cross-Sectional Studies (AXIS tool) indicated that most studies were rated as moderate to strong quality (84%).

CONCLUSION

Findings indicate that elevated reward sensitivity may be a risk factor for engagement in eating behaviors that may increase obesity risk.

A questionnaire to assess eating behavior: Structure, validity and responsiveness of a new German eating behavior scale (SEV)

Numerous weight-loss interventions promoting healthy and weight-reducing eating behavior have been developed over the past years. To evaluate the effectiveness of such interventions for eating behavior change, short, validated and sensitive instruments are needed. In this study series, we developed and validated a new outcome measure to assess health-conscious and weight-controlling eating behavior for the evaluation of weight-loss interventions. The preliminary version of the German eating behavior scale (Skala zumErnährungsverhalten [SEV]) included 40 items. Three studies were conducted to (a) reduce the preliminary item pool, (b) investigate structural validity and internal consistency using exploratory and confirmatory factor analyses (EFA, CFA), as well as McDonald's ω, and (c) test construct validity with physiological and behavioral parameters. Responsiveness to change was also assessed after a 12-week weight-loss intervention. EFA indicated a two-factor solution with health-conscious (hc-EB) and weight-controlling eating behavior (wc-EB) as subscales, CFA confirmed the two-factor solution with acceptable model fit. Internal consistencies of both subscales were also acceptable to good (hc-EB: ω = 0.88; wc-EB: ω = 0.78). Significantly small to moderate correlations to the Healthy Eating Index (r = 0.51) as well as blood glucose (r = 0.31), blood lipids (r = 0.23), and vascular age (r = 0.31) were found, supporting the construct validity of the SEV and its subscales. Both subscales detected intervention-related changes in eating behavior among subjects of a weight-loss intervention with Standardized Response Means of 0.52 and 0.67, indicating good responsiveness of the SEV. In sum, findings provide evidence that the SEV is a valid and responsive measure to assess health-conscious and weight-controlling eating behavior.

Longitudinal geo-referenced field evidence for the heightened BMI responsiveness of obese women to price discounts on carbonated soft drinks

There is increasing interest in the effect that food environments may have on obesity, particularly through mechanisms related to the marketing and consumption of calorie-dense, nutrient-poor foods and sugary beverages. Price promotions, such as temporary price discounts, have been particularly effective in the marketing of carbonated soft drinks (CSDs) among consumers. Research has also suggested that the purchasing behavior of consumer groups may be differentially sensitive to price discounts on CSDs, with obese women particularly sensitive. In addition, the intensity of price discount in a person's food environment may also vary across geography and over time. This study examines whether the weight change of obese women, compared to overweight or normal BMI women, is more sensitive to the intensity of price discounts on CSDs in the food environment. This study used longitudinal survey data from 1622 women in the Montreal Neighborhood Networks and Health Aging (MoNNET-HA) Panel. Women were asked to report their height and weight in 2008, 2010 and 2013 in order to calculate women's BMI in 2008 and their change of weight between 2008 and 2013. Women's exposure to an unhealthy food environment was based on the frequency in which their neighborhood food stores placed price discounts on CSDs in 2008. The price discount frequency on CSDs within women's neighborhoods was calculated from Nielsen point-of sales transaction data in 2008 and geocoded to participant's forward sortation area. The prevalence of obesity and overweight among MoNNET-HA female participants was 18.3% in 2008, 19.9% in 2010 and 20.7% in 2013 respectively. Results showed that among obese women, exposure to unhealthy food environments was associated with a 3.25 kilogram (SE = 1.35, p-value = 0.02) weight gain over the five-year study period. Exposure to price discounts on CSDs may disproportionately affect and reinforce weight gain in women who are already obese.

Executive Functions of Adults with Binge-Eating Disorder: The Role of Weight Status and Psychopathology

Findings on executive functions (EFs) in binge-eating disorder (BED) are inconsistent and possibly biased by associated comorbidities. This study aimed to identify whether distinct levels of physical and mental comorbidity are related to EFs in BED. General and food-specific EFs in n = 77 adults with BED were compared to population-based norms and associations with weight status, depressive symptoms, and eating disorder psychopathology were analyzed. To detect within-sample patterns of EF performance, k-means clustering was applied. The results indicated that participants' general EFs were within the average range with slight deficits in alertness. While depression and eating disorder psychopathology were unrelated to EFs, weight status was associated with food-specific attentional bias that was significantly higher in obesity class 2 than in overweight/obesity class 1 and obesity class 3. Four meaningful clusters with distinct strengths and impairments in general and food-specific EFs but without differences in clinical variables were identified. Altogether, adults with BED showed few specific deficits compared to normative data. Performance was unrelated to depression and eating disorder psychopathology, while weight status was associated with food-specific EFs only. The results highlight the need for longitudinal studies to evaluate the relevance of EFs in BED development and maintenance in neurologically healthy adults.

Binge Watching during COVID-19: Associations with Stress and Body Weight

Binge watching is becoming increasingly common and may impact energy balance and body weight. The COVID-19 pandemic has created conditions conducive to binge watching and increased stress. We investigated relationships between COVID-related stress and binge watching behaviors, and potential variation in this relationship by body weight. Adults (n = 466) completed a cross-sectional online survey assessing binge watching behaviors during and before the pandemic, COVID-related stress, and body weight. Participants reported an increase in binge watching frequency from before to during the pandemic (F1,401 = 99.970, p < 0.001), with rates of high binge watching ("3-4 times per week" to "3 or more times per day") increasing from 14.6% to 33.0%. Binge watching episode duration increased from 3.26 ± 1.89 h to 3.92 ± 2.08 h (p < 0.001). The increase in binge watching frequency was greatest in individuals with obesity and high stress (F 4,401 = 4.098, p = 0.003). Participants reporting high stress reported higher frequency of eating while binge watching, as well as higher levels of negative emotional triggers, consequences to binge watching, and lack of control over binge watching (all p < 0.001). Our results show that binge watching increased during the pandemic, with greater increases among individuals reporting higher COVID-related stress, especially those with obesity, and concomitant effects on eating, and highlight a need for interventions to minimize the obesogenic impact of binge watching during the pandemic.

Are Sensitivity to Punishment, Sensitivity to Reward and Effortful Control Transdiagnostic Mechanisms Underlying the Eating Disorder/Obesity Spectrum?

Although it has been postulated that eating disorders (EDs) and obesity form part of a broad spectrum of eating- and weight-related disorders, this has not yet been tested empirically. In the present study, we investigated interindividual differences in sensitivity to punishment, sensitivity to reward, and effortful control along the ED/obesity spectrum in women. We used data on 286 patients with eating disorders (44.6% AN-R, 24.12% AN-BP, and 31.82% BN), 126 healthy controls, and 640 Class II/III obese bariatric patients (32.81% Class II and 67.19% Class III) with and without binge eating. Participants completed the behavioral inhibition and behavioral activation scales, as well as the effortful control scale, to assess sensitivity to punishment and reward and effortful control. Results showed that patients with EDs scored significantly higher on punishment sensitivity (anxiety) compared to healthy controls and Class II/III obese patients; the different groups did not differ significantly on reward sensitivity. Patients with binge eating or compensatory behaviors scored significantly lower on effortful control than patients without binge eating. Differences in temperamental profiles along the ED/obesity spectrum appear continuous and gradual rather than categorical. This implies that it may be meaningful to include emotion regulation and impulse regulation training in the treatment of both EDs and obesity.

A dismantling study on imaginal retraining in overweight or obese women

Imaginal retraining is a variant of approach bias modification and transfers the method into one's own mind. As the technique contains multiple elements, this pilot study aimed to dismantle which of its components is most efficient in reducing craving for high-calorie food. A total of 113 women were randomly allocated to one out of six conditions containing a short intervention to mentally manipulate a picture displaying high-calorie foods. Four of the interventions involved different combinations of elements of the imaginal retraining technique, while the remaining two conditions comprised thought suppression or merely observing a picture. Participants rated their level of craving, as well as three pictures containing healthy and unhealthy foods regarding their pleasantness before and after the interventions took place. Within-group changes were assessed with paired t-tests (in case of non-normal data Wilcoxon paired t-tests) and between-group differences with one-way ANOVAs (non-parametric Kruskal-Wallis tests). A trend level reduction in craving was found in the imaginal retraining condition with and without a movement. A post hoc analysis of both conditions joint together showed a statistically significant reduction in craving. In addition, positive picture appraisal for unhealthy foods was significantly reduced in both imaginal retraining conditions (with and without movement) with medium to large effect sizes. This study demonstrated that imaginal retraining with an arm movement can reduce craving and picture appraisal for high-calorie foods significantly in a one-time application. It is a promising technique to reduce appraisal for unhealthy high-calorie foods. Future studies should repeat the experiment in situations of high craving and allow for a personalized selection of stimuli.

Reliance on model-based and model-free control in obesity

Consuming more energy than is expended may reflect a failure of control over eating behaviour in obesity. Behavioural control arises from a balance between two dissociable strategies of reinforcement learning: model-free and model-based. We hypothesized that weight status relates to an imbalance in reliance on model-based and model-free control, and that it may do so in a linear or quadratic manner. To test this, 90 healthy participants in a wide BMI range [normal-weight (n = 31), overweight (n = 29), obese (n = 30)] performed a sequential decision-making task. The primary analysis indicated that obese participants relied less on model-based control than overweight and normal-weight participants, with no difference between overweight and normal-weight participants. In line, secondary continuous analyses revealed a negative linear, but not quadratic, relationship between BMI and model-based control. Computational modelling of choice behaviour suggested that a mixture of both strategies was shifted towards less model-based control in obese participants. Our findings suggest that obesity may indeed be related to an imbalance in behavioural control as expressed in a phenotype of less model-based control potentially resulting from enhanced reliance on model-free computations.

The Obesity-Susceptibility Gene TMEM18 Promotes Adipogenesis through Activation of PPARG

TMEM18 is the strongest candidate for childhood obesity identified from GWASs, yet as for most GWAS-derived obesity-susceptibility genes, the functional mechanism remains elusive. We here investigate the relevance of TMEM18 for adipose tissue development and obesity. We demonstrate that adipocyte TMEM18 expression is downregulated in children with obesity. Functionally, downregulation of TMEM18 impairs adipocyte formation in zebrafish and in human preadipocytes, indicating that TMEM18 is important for adipocyte differentiation in vivo and in vitro. On the molecular level, TMEM18 activates PPARG, particularly upregulating PPARG1 promoter activity, and this activation is repressed by inflammatory stimuli. The relationship between TMEM18 and PPARG1 is also evident in adipocytes of children and is clinically associated with obesity and adipocyte hypertrophy, inflammation, and insulin resistance. Our findings indicate a role of TMEM18 as an upstream regulator of PPARG signaling driving healthy adipogenesis, which is dysregulated with adipose tissue dysfunction and obesity.

The role of reward sensitivity in obesity and its association with Transcription Factor AP-2B: A longitudinal birth cohort study

OBJECTIVE

One factor potentially contributing to obesity is reward sensitivity. We investigated the association between reward sensitivity and measures of obesity from 9-33 years of age, paying attention to the inner structure of reward sensitivity.

METHODS

The sample included both birth cohorts (originally n = 1176) of the Estonian Children Personality Behaviour and Health Study. The association between reward sensitivity and measures of obesity was assessed using mixed-effects regression models. Associations at ages 9 (younger cohort only), 15, 18, 25 and 33 (older cohort) years were analyzed by one-way ANOVA. The indirect effect of the gene encoding transcription factor 2 beta (TFAP2B) on obesity through reward sensitivity was tested using mediation analysis.

RESULTS

According to linear mixed effects regression models, an increase in scores of Insatiability by Reward and both of its components, Excessive Spending and Giving in to Cravings, significantly increased body weight, body mass index, sum of five skinfolds, waist circumference, hip circumference and waist-to-height ratio from 15 to 25 years of age. Findings were similar at age 9 and 33 years. In contrast, no association between obesity and Openness to Rewards or its facets was observed. The TFAP2B genotype was also associated with fixation to rewards in females, but not with striving towards reward multiplicity.

CONCLUSION

Our results suggest that reward sensitivity is associated with obesity by its reward fixation component. The heterogeneity of the reward sensitivity construct should be taken into account in studies on body composition.

Risk of Excess and Inadequate Gestational Weight Gain among Hispanic Women: Effects of Immigration Generational Status

There is a dearth of information on the risk of inadequate and excess gestational weight gain (GWG) among different generations of Hispanic women in the United States. Therefore, the objective of this study was to understand the relationship of GWG and immigration across three generations of Hispanic women. The study was conducted using data from National Longitudinal Survey of Youth 1979 (NLSY79). The study sample included 580 (unweighted count) women (148 first-generation, 117 second-generation, and 315 third-/higher-generation). Sociodemographic and immigration data were extracted from the main NLSY79 survey, and pregnancy data were extracted from the child/young adult survey following the biological children born to women in NLSY79. Covariate adjusted weighted logistic regression models were conducted to assess the risk of inadequate and excess GWG among the groups. Average total GWG was 14.98 kg, 23% had inadequate GWG, and 50% had excess GWG. After controlling for the covariates, there was no difference in the risk of inadequate GWG between the three generations. First-generation women (OR = 0.47, p = 0.039) and third-/higher-generation women (OR = 0.39, p = 0.004) had significantly lower risk of excess GWG compared to second-generation women. It is important to recognize the generational status of Hispanic women as a risk factor for excess GWG.

The interplay between binge eating risk factors: Toward an integrated model

We aimed to assess the interplay between dietary restraint and emotion regulation (ER) difficulties as well as other well-known risk factors of binge eating in a community sample of women. Altogether 96 women (mean age 21.5 years; mean BMI 21.7) participated in the study using ecological momentary assessment. Structural equation modeling indicated that restraint and ER pathways are related yet operate independently in predicting binge eating in a unified model. ER difficulties moderated the effect of negative affect and fluctuations in negative affect in predicting binge eating while Neuroticism and preoccupation with body weight predicted binge eating indirectly.

Fetal Programming by Methyl Donors Modulates Central Inflammation and Prevents Food Addiction-Like Behavior in Rats

Fetal programming by hypercaloric intake leads to food addiction-like behavior and brain pro-inflammatory gene expression in offspring. The role of methylome modulation during programming on central immune activation and addiction-like behavior has not been characterized. We employed a nutritional programming model exposing female Wistar rats to chow diet, cafeteria (CAF), or CAF-methyl donor’s diet from pre-pregnancy to weaning. Addiction-like behavior in offspring was characterized by the operant training response using Skinner boxes. Food intake in offspring was determined after fasting–refeeding schedule and subcutaneous injection of ghrelin. Genome-wide DNA methylation in the nucleus accumbens (NAc) shell was performed by fluorescence polarization, and brain immune activation was evaluated using real-time PCR for pro-inflammatory cytokines (IL-1β, TNF-1α, and IL-6). Molecular effects of methyl modulators [S-adenosylmethionine (SAM) or 5-azatidine (5-AZA)] on pro-inflammatory cytokine expression and phagocytosis were identified in the cultures of immortalized SIM-A9 microglia cells following palmitic acid (100 μM) or LPS (100 nM) stimulation for 6 or 24 h. Our results show that fetal programming by CAF exposure increases the number of offspring subjects and reinforcers under the operant training response schedule, which correlates with an increase in the NAc shell global methylation. Notably, methyl donor’s diet selectively decreases lever-pressing responses for reinforcers and unexpectedly decreases the NAc shell global methylation. Also, programmed offspring by CAF diet shows a selective IL-6 gene expression in the NAc shell, which is reverted to control values by methyl diet exposure. In vitro analysis identified that LPS and palmitic acid activate IL-1β, TNF-1α, and IL-6 gene expression, which is repressed by the methyl donor SAM. Finally, methylation actively represses phagocytosis activity of SIM-A9 microglia cells induced by LPS and palmitic acid stimulation. Our in vivo and in vitro data suggest that fetal programming by methyl donors actively decreases addiction-like behavior to palatable food in the offspring, which correlates with a decrease in NAc shell methylome, expression of pro-inflammatory cytokine genes, and activity of phagocytic microglia. These results support the role of fetal programming in brain methylome on immune activation and food addiction-like behavior in the offspring.

Individual Differences in Hippocampal Volume as a Function of BMI and Reward Sensitivity

Sensitivity to reward is a personality trait that predisposes a person to several addictive behaviors, including the presence of different risky behaviors that facilitates uncontrolled eating. However, the multifactorial nature of obesity blurs a direct relationship between the two factors. Here, we studied the brain anatomic correlates of the interaction between reward sensitivity and body mass index (BMI) to investigate whether the coexistence of high BMI and high reward sensitivity structurally alters brain areas specifically involved in the regulation of eating behavior. To achieve this aim, we acquired T1-weighted images and measured reward sensitivity using the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSRQ) and BMI in a sample of 206 adults. Results showed that reward sensitivity and BMI were not significantly correlated. However, neuroimaging results confirmed a relationship between BMI and reduced volume in the medial and lateral orbitofrontal cortex, and between reward sensitivity and lower striatum volume. Importantly, the interaction between the two factors was significantly related to the right anterior hippocampus volume, showing that stronger reward sensitivity plus a higher BMI were associated with reduced hippocampal volume. The hippocampus is a brain structure involved in the higher-order regulation of feeding behavior. Thus, a dysfunctional hippocampus may contribute to maintaining a vicious cycle that predisposes people to obesity.

Enhanced Go and NoGo Learning in Individuals With Obesity

Overeating in individuals with obesity is hypothesized to be partly caused by automatic action tendencies to food cues that have the potential to override goal-directed dietary restriction. Individuals with obesity are often characterized by alterations in the processing of such rewarding food, but also of non-food stimuli, and previous research has suggested a stronger impact on the execution of goal-directed actions in obesity. Here, we investigated whether Pavlovian cues can also corrupt the learning of new approach or withdrawal behavior in individuals with obesity. We employed a probabilistic Pavlovian-instrumental learning paradigm in which participants (29 normal-weight and 29 obese) learned to actively respond (Go learning) or withhold a response (NoGo learning) in order to gain monetary rewards or avoid losses. Participants were better at learning active approach responses (Go) in the light of anticipated rewards and at learning to withhold a response (NoGo) in the light of imminent punishments. Importantly, there was no evidence for a stronger corruption of instrumental learning in individuals with obesity. Instead, they showed better learning across conditions than normal-weight participants. Using a computational reinforcement learning model, we additionally found an increased learning rate in individuals with obesity. Previous studies have mostly reported a lower reinforcement learning performance in individuals with obesity. Our results contradict this and suggest that their performance is not universally impaired: Instead, while previous studies found reduced stimulus-value learning, individuals with obesity may show better action-value learning. Our findings highlight the need for a broader investigation of behavioral adaptation in obesity across different task designs and types of reinforcement learning.

Double jeopardy: Comorbid obesity and cigarette smoking are linked to neurobiological alterations in inhibitory control during smoking cue exposure

Obesity and cigarette smoking are two of the leading preventable causes of death in the United States. Research suggests that overlapping pathophysiology may contribute to obesity and nicotine use disorder (NUD), yet no studies have investigated the effect of obesity on neural response to reward stimuli in NUD. This study used arterial spin-labeled perfusion functional magnetic resonance imaging (fMRI) to examine neural responses during exposure to smoking versus nonsmoking cues in 79 treatment-seeking participants with NUD, 26 with normal weight, 28 with overweight, and 25 with obesity. Given that deficits in behavioral inhibitory control have been associated with both obesity and NUD, participants completed an affect-congruent Go/NoGo task to assess the effect of body mass index (BMI) on this construct in NUD. Analyses revealed that BMI was negatively associated with activation in the right dorsolateral prefrontal cortex (dlPFC) in response to smoking cues, with significantly reduced response in smokers with overweight and smokers with obesity compared with normal-weight smokers. In addition, greater commission errors on the Go/NoGo task were correlated with reduced neural response to smoking cues in the right dlPFC only among those with obesity. Together, these findings provide evidence that obesity in treatment-seeking NUDs is related to neurobiological alterations in inhibitory control over cue-potentiated behaviors, suggesting that smoking cessation may be more difficult in individuals with comorbid NUD and obesity than in those without, requiring treatment strategies tailored to meet their unique needs.

Hemispheric asymmetries in resting-state EEG and fMRI are related to approach and avoidance behaviour, but not to eating behaviour or BMI

Much of our behaviour is driven by two motivational dimensions—approach and avoidance. These have been related to frontal hemispheric asymmetries in clinical and resting‐state EEG studies: Approach was linked to higher activity of the left relative to the right hemisphere, while avoidance was related to the opposite pattern. Increased approach behaviour, specifically towards unhealthy foods, is also observed in obesity and has been linked to asymmetry in the framework of the right‐brain hypothesis of obesity. Here, we aimed to replicate previous EEG findings of hemispheric asymmetries for self‐reported approach/avoidance behaviour and to relate them to eating behaviour. Further, we assessed whether resting fMRI hemispheric asymmetries can be detected and whether they are related to approach/avoidance, eating behaviour and BMI. We analysed three samples: Sample 1 (n = 117) containing EEG and fMRI data from lean participants, and Samples 2 (n = 89) and 3 (n = 152) containing fMRI data from lean, overweight and obese participants. In Sample 1, approach behaviour in women was related to EEG, but not to fMRI hemispheric asymmetries. In Sample 2, approach/avoidance behaviours were related to fMRI hemispheric asymmetries. Finally, hemispheric asymmetries were not related to either BMI or eating behaviour in any of the samples. Our study partly replicates previous EEG findings regarding hemispheric asymmetries and indicates that this relationship could also be captured using fMRI. Our findings suggest that eating behaviour and obesity are likely to be mediated by mechanisms not directly relating to frontal asymmetries in neuronal activation quantified with EEG and fMRI.

No Differential Reward Responsivity and Drive, Punishment Sensitivity or Attention for Cues Signaling Reward or Punishment in Adolescents With Obesity

Although it has been proposed that obese and healthy weight individuals might differ in their reward and punishment sensitivity, the literature shows diverse and inconsistent findings. The current study was set out to examine the role of reward and punishment sensitivity in adolescent obesity by differentiating between reward responsivity and reward drive, and by complementing self-report measures with performance-based measures indexing attention for cues signaling reward and punishment as well as effort to approach reward and avoid punishment. Participants were adolescents aged 12-23, with obesity (n = 51, adjusted BMI [(actual BMI/Percentile 50 of BMI for age and gender) × 100) between 143 and 313%], and with a healthy weight (n = 51, adjusted BMI between 75 and 129%). Individuals with obesity did not significantly differ from adolescents with a healthy weight in reward responsivity, reward drive or attention to cues signaling reward. Further, no differences in self-reported punishment sensitivity or attention for cues signaling punishment were found between obese and healthy weight adolescents. The current study thus does not corroborate the theories that general reward and punishment sensitivity play a role in obesity.

What Difference Does it Make? Risk-Taking Behavior in Obesity after a Loss is Associated with Decreased Ventromedial Prefrontal Cortex Activity

Altered activity in decision-making neural circuitry may underlie the maladaptive food choices found in obesity. Here, we aimed to identify the brain regions purportedly underpinning risk-taking behavior in individuals with obesity. Twenty-three adult women with obesity and twenty-three healthy weight controls completed the Risky Gains Task during functional magnetic resonance imaging (fMRI). This task allows participants to choose between a safe option for a small, guaranteed monetary reward and risky options with larger rewards. fMRI analyses comparing losing trials to winning trials found that participants with obesity presented decreased activity in the left anterior insula in comparison to controls (p < 0.05, AlphaSim corrected). Moreover, left insula activation during losses vs. wins was negatively correlated with UPPS-P questionnaire sensation seeking scores. During safe vs. risky trials following a loss, the control group exhibited increased activation in the ventromedial prefrontal cortex (vmPFC) (p < 0.05, AlphaSim corrected) in comparison to the OB group. Moreover, vmPFC response in the obesity group during post-loss trials was negatively correlated with risky choices on the task overall. As a whole, our findings support that diminished tuning of the insula towards interoceptive signals may lead to a lack of input to the vmPFC when weighing the costs and benefits of risky choices.

Appetitive Pavlovian-to-Instrumental Transfer in Participants with Normal-Weight and Obesity

Altered eating behavior due to modern, food-enriched environments has a share in the recent obesity upsurge, though the exact mechanisms remain unclear. This study aims to assess whether higher weight or weight gain are related to stronger effects of external cues on motivation-driven behavior. 51 people with and without obesity completed an appetitive Pavlovian-to-Instrumental Transfer (PIT) paradigm. During training, button presses as well as presentation of fractal images resulted in three palatable and one neutral taste outcome. In the subsequent test phase, outcome-specific and general behavioral bias of the positively associated fractal images on deliberate button press were tested under extinction. While all participants showed signs of specific transfer, general transfer was not elicited. Contrary to our expectations, there was no main effect of weight group on PIT magnitude. Participants with obesity exhibited higher scores in the Three-Factor Eating Questionnaire Disinhibition scale, replicating a very robust effect from previous literature. Individual Restraint scores were able to predict body-mass index (BMI) change after a three-year period. Our data indicate that PIT is an important player in how our environment influences the initiation of food intake, but its effects alone cannot explain differences in-or future development of-individual weight.

Association between sex and body mass index as mediated by temperament in a nonclinical adult sample

PURPOSE

The main purpose of the present study was to investigate the association between sex and body mass index (BMI) as mediated by the temperament traits postulated by the regulative theory of temperament.

METHODS

A group of 317 subjects, including 122 men and 195 women 18-82 years old (M = 31.93; SD = 12.64 years), was recruited from the general population to participate in the study. A cross-sectional design was applied in this study. Temperament was assessed using the formal characteristics of behaviour-temperament inventory revised version (FCB-TIR). In the sample, BMIs ranged from 16.51 to 35.56 kg/m² (M = 23.31 kg/m²; SD = 3.61 kg/m²).

RESULTS

The male group had significantly higher BMI, briskness and endurance levels and significantly lower perseveration, sensory sensitivity and emotional reactivity levels compared to the female group. No significant differences between these groups were noted in terms of activity and rhythmicity. The correlations between BMI and briskness and between BMI and endurance were positive, while the correlations between BMI and perseveration and between BMI and activity were negative. The correlations among BMI, sensory sensitivity, emotional reactivity and rhythmicity were not statistically significant. The mediation analysis showed that briskness and endurance were significant partial mediators of the relationship between sex and BMI.

CONCLUSIONS

Sex and two temperament traits, briskness and endurance, were the best predictors of BMI. Briskness and endurance partially mediated the relationship between sex and BMI.

LEVEL OF EVIDENCE

Descriptive cross-sectional study. Level V.

Altered monetary loss processing and reinforcement-based learning in individuals with obesity

Individuals with obesity are often characterized by alterations in reward processing. This may affect how new information is used to update stimulus values during reinforcement-based learning. Here, we investigated obesity-related changes in non-food reinforcement processing, their impact on learning performance as well as the neural underpinnings of reinforcement-based learning in obesity. Nineteen individuals with obesity (BMI > = 30 kg/m², 10 female) and 23 lean control participants (BMI 18.5–24.9 kg/m², 11 female) performed a probabilistic learning task during functional magnetic resonance imaging (fMRI), in which they learned to choose between advantageous and disadvantageous choice options in separate monetary gain, loss, and neutral conditions. During learning individuals with obesity made a significantly lower number of correct choices and accumulated a significantly lower overall monetary outcome than lean control participants. FMRI analyses revealed aberrant medial prefrontal cortex responses to monetary losses in individuals with obesity. There were no significant group differences in the regional representation of prediction errors. However, we found evidence for increased functional connectivity between the ventral striatum and insula in individuals with obesity. The present results suggest that obesity is associated with aberrant value representations for monetary losses, alterations in functional connectivity during the processing of learning outcomes, as well as a decresased reinforcement-based learning performance. This may affect how new information is incorporated to adjust dysfunctional behavior and could be a factor contributing to the maintenance of dysfunctional eating behavior in obesity.

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Dorsolateral and medial prefrontal cortex mediate the influence of incidental priming on economic decision making in obesity

Obese individuals discount future rewards to a higher degree than lean individuals, which is generally considered disadvantageous. Moreover, their decisions are altered more easily by decision-irrelevant cues. Here, we investigated neural correlates of this phenomenon using functional MRI. We tested 30 lean and 26 obese human subjects on a primed delay discounting paradigm using gustatory and visual cues of positive, neutral and negative valence to bias their intertemporal preferences. We hypothesised that activation differences in reward-related and behavioural control areas, and changes in connectivity between these areas, would reflect the effect of these cues. Here, obese subjects were more susceptible to priming with negative gustatory cues towards delayed choices as opposed to lean subjects. This was related to lower activity in the left dorsolateral prefrontal cortex during priming. Modulation of functional connectivity between the dlPFC and the ventromedial PFC by the behavioural priming effect correlated negatively with BMI. This might indicate that default goals of obese individuals were different from those of lean participants, as the dlPFC has been suggested to be involved in internal goal pursuit. The present results further our understanding of the role of the PFC in decision-making and might inform future weight-management approaches based on non-invasive brain stimulation.

Feasibility and impact study of a reward-based mobile application to improve adolescents' snacking habits

OBJECTIVE

Adolescents' snacking habits are driven by both explicit reflective and implicit hedonic processes. Hedonic pathways and differences in sensitivity to food rewards in addition to reflective determinants should be considered. The present study evaluated the feasibility and impact of a mobile phone-delivered intervention, incorporating explicit reflective and implicit rewarding strategies, on adolescents' snack intake.

DESIGN

Adolescents (n 988; mean age 14·9 (sd 0·70) years, 59·4 % boys) completed a non-randomized clustered controlled trial. Adolescents (n 416) in the intervention schools (n 3) were provided with the intervention application for four weeks, while adolescents (n 572) in the control schools (n 3) followed the regular curriculum. Outcomes were differences in healthy snacking ratio and key determinants (awareness, intention, attitude, self-efficacy, habits and knowledge). Process evaluation data were collected via questionnaires and through log data of the app.

RESULTS

No significant positive intervention effects on the healthy snack ratio (b=-3·52 (se 1·82), P>0·05) or targeted determinants were observed. Only 268 adolescents started using the app, of whom only fifty-five (20·5 %) still logged in after four weeks. Within the group of users, higher exposure to the app was not significantly associated with positive intervention effects. App satisfaction ratings were low in both high and low user groups. Moderation analyses revealed small positive intervention effects on the healthy snack ratio in high compared with low reward-sensitive boys (b=1·38 (se 0·59), P<0·05).

CONCLUSIONS

The intervention was not able to improve adolescents' snack choices, due to low reach and exposure. Future interventions should consider multicomponent interventions, teacher engagement, exhaustive participatory app content development and tailoring.

A narrative review of the construct of hedonic hunger and its measurement by the Power of Food Scale

INTRODUCTION

The term 'hedonic hunger' refers to one's preoccupation with and desire to consume foods for the purposes of pleasure and in the absence of physical hunger. The Power of Food Scale (PFS) was developed as a quantitative measure of this construct in 2009. Since then, over 50 published studies have used the PFS to predict appetite-related outcomes including neural, cognitive, behavioural, anthropometric and clinical measures.

OBJECTIVE

This narrative review evaluates how closely the PFS captures the construct it was originally presumed to assess and to more clearly define hedonic hunger itself.

METHODS

The measure's relationship to four domains is reviewed and summarized: motivation to consume palatable foods; level of actual consumption of such foods; body mass; and subjective loss-of-control over one's eating behaviour. Findings are synthesized to generate a more accurate understanding of what the PFS measures and how it may relate to the broader definition of hedonic hunger.

RESULTS

Results suggest that the PFS is closely related to motivation to consume palatable foods and, in extreme cases, occurrence of loss-of-control eating episodes. PFS scores are not consistently predictive of amount of food consumed or body mass.

CONCLUSIONS

Implications of these findings are discussed in the context of behavioural health, and avenues for further inquiry are identified.

A predictive model of rat calorie intake as a function of diet energy density

Easy access to high-energy food has been linked to high rates of obesity in the world. Understanding the way that access to palatable (high fat or high calorie) food can lead to overconsumption is essential for both preventing and treating obesity. Although the body of studies focused on the effects of high-energy diets is growing, our understanding of how different factors contribute to food choices is not complete. In this study, we present a mathematical model that can predict rat calorie intake to a high-energy diet based on their ingestive behavior to a standard chow diet. Specifically, we propose an equation that describes the relation between the body weight ( W), energy density ( E), time elapsed from the start of diet ( T), and daily calorie intake ( C). We tested our model on two independent data sets. Our results show that the suggested model can predict the calorie intake patterns with high accuracy. Additionally, the only free parameter of our proposed equation (ρ), which is unique to each animal, has a strong correlation with their calorie intake.

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

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

The association between in vivo central noradrenaline transporter availability and trait impulsivity

The brain noradrenaline (NA) system, particularly NA transporters (NAT), are thought to play an important role in modulating impulsive behavior. Impaired impulsivity is implicated in a variety of neuropsychiatric conditions; however, an in vivo link between central NAT availability and human impulsivity has not been shown. Using positron emission tomography (PET) and S,S-[¹¹C]O-methylreboxetine (MRB), we tested whether NAT availability is associated with this basic behavioral trait based on the Barratt Impulsiveness Scale (BIS-11) in twenty healthy individuals (12 females, 33.8±9.3, 21-52 years of age) with a body mass index (BMI) ranging from 21.7kg/m² to 47.8kg/m². Applying both voxel-wise and volume-of-interest (VOI) based analyses, we found that distribution volume ratios (DVR) used as PET outcome measures negatively correlated with BIS-11 total scores in the orbitofrontal cortex (OFC) and in the hippocampus as well as in parts of the cerebellar cortex. These associations however did not remain after correction for multiple testing. Thus, although it appears that low NAT availability is associated with greater scores of impaired behavioral control, this needs to be confirmed in a larger series of individuals with highly impulsive behavior.

Serotonin transporter gene promoter methylation status correlates with in vivo prefrontal 5-HTT availability and reward function in human obesity

A polymorphism in the promoter region of the human serotonin transporter (5-HTT)-coding SLC6A4 gene (5-HTTLPR) has been implicated in moderating susceptibility to stress-related psychopathology and to possess regulatory functions on human in vivo 5-HTT availability. However, data on a direct relation between 5-HTTLPR and in vivo 5-HTT availability have been inconsistent. Additional factors such as epigenetic modifications of 5-HTTLPR might contribute to this association. This is of particular interest in the context of obesity, as an association with 5-HTTLPR hypermethylation has previously been reported. Here, we tested the hypothesis that methylation rates of 14 cytosine-phosphate-guanine (CpG) 5-HTTLPR loci, in vivo central 5-HTT availability as measured with [¹¹C]DASB positron emission tomography (PET) and body mass index (BMI) are related in a group of 30 obese (age: 36±10 years, BMI>35 kg/m²) and 14 normal-weight controls (age 36±7 years, BMI<25 kg/m²). No significant association between 5-HTTLPR methylation and BMI overall was found. However, site-specific elevations in 5-HTTLPR methylation rates were significantly associated with lower 5-HTT availability in regions of the prefrontal cortex (PFC) specifically within the obese group when analyzed in isolation. This association was independent of functional 5-HTTLPR allelic variation. In addition, negative correlative data showed that CpG10-associated 5-HTT availability determines levels of reward sensitivity in obesity. Together, our findings suggest that epigenetic mechanisms rather than 5-HTTLPR alone influence in vivo 5-HTT availability, predominantly in regions having a critical role in reward processing, and this might have an impact on the progression of the obese phenotype.

Overlapping Neural Endophenotypes in Addiction and Obesity

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

Caudate-Precuneus Functional Connectivity Is Associated with Obesity Preventive Eating Tendency

There exists diversity among individuals in difficulty controlling body weight. Body weight control, or obesity prevention, requires cognitive control over ingestive behavior, which may account for the diverse ability of body weight control. The caudate nuclei, especially the dorsal area, have been shown to play critical roles in ingestive behaviors, which significantly influences body weight control. However, the practice of body weight control is dependent on the body weight status, because the current obesity status determines the need for body weight control. To elucidate the underlying neural mechanism that accounts for individual differences in obesity prevention, we aimed to isolate functional caudate connectivity responsible for the underlying tendency of obesity prevention, independent of the current obesity status, using resting state fMRI data, body mass index (BMI), and assessment of ingestive behavior from 185 individuals from the NKI-Rockland sample. The underlying tendency of obesity prevention was estimated from BMI and behavioral and cognitive components of food intake. Functional connectivities between the caudate head and the whole brain were tested as a function of the estimated tendency in a voxel-wise manner. The bilateral precuneus showed inverse association between its connectivity to the caudate and the estimated tendency. Caudate-precuneus connectivity may have significant implications to understanding personal differences that accounts for the success in body weight control.

Association between Impulsivity and Weight Status in a General Population

The objective of this study is to examine the association between impulsivity and weight status in a large sample of the adult general population in France, and the influence of gender on this relationship. A total of 11,929 men and 39,114 women participating in the NutriNet-Santé cohort were selected in this cross-sectional analysis. The Barratt Impulsiveness Scale (BIS-11) was used to assess impulsivity. Weight and height were self-reported. The association between impulsivity and BMI was estimated using logistic regressions adjusted for socio-demographic and lifestyle factors. Individuals with high impulsivity levels (BIS-11 total score >71) were more likely to be obese (Odds Ratio (OR) = 1.80, 95% Confidence Interval (CI): 1.39, 2.33 in men; OR = 1.30, 95% CI: 1.15, 1.48 in women) compared to individuals in the average range of impulsivity. The strongest associations between impulsivity and obesity were observed in men, where highly impulsive participants were more likely to be class III obese (BMI > 40 kg/m²) (OR = 3.57, 95% CI: 1.86, 6.85). This large sample analysis supports the existence of a relationship between impulsivity and weight status and the importance of psychological factors in the prevention of obesity.

Food-Predicting Stimuli Differentially Influence Eye Movements and Goal-Directed Behavior in Normal-Weight, Overweight, and Obese Individuals

Obese individuals have been shown to exhibit abnormal sensitivity to rewards and reward-predicting cues as for example food-associated cues frequently used in advertisements. It has also been shown that food-associated cues can increase goal-directed behavior but it is currently unknown, whether this effect differs between normal-weight, overweight, and obese individuals. Here, we investigate this question by using a Pavlovian-to-instrumental transfer (PIT) task in normal-weight (N = 20), overweight (N = 17), and obese (N = 17) individuals. Furthermore, we applied eye tracking during Pavlovian conditioning to measure the participants' conditioned response as a proxy of the incentive salience of the predicted reward. Our results show that the goal-directed behavior of overweight individuals was more strongly influenced by food-predicting cues (i.e., stronger PIT effect) than that of normal-weight and obese individuals (p < 0.001). The weight groups were matched for age, gender, education, and parental education. Eye movements during Pavlovian conditioning also differed between weight categories (p < 0.05) and were used to categorize individuals based on their fixation style into "high eye index" versus "low eye index" as well. Our main finding was that the fixation style exhibited a complex interaction with the weight category. Furthermore, we found that normal-weight individuals of the group "high eye index" had higher body mass index within the healthy range than individuals of the group "low eye index" (p < 0.001), but this relationship was not found within in the overweight or obese groups (p > 0.646). Our findings are largely consistent with the incentive sensitization theory predicting that overweight individuals are more susceptible to food-related cues than normal-weight controls. However, this hypersensitivity might be reduced in obese individuals, possibly due to habitual/compulsive overeating or differences in reward valuation.

Neuronal systems and circuits involved in the control of food intake and adaptive thermogenesis

With the still-growing prevalence of obesity worldwide, major efforts are made to understand the various behavioral, environmental, and genetic factors that promote excess fat gain. Obesity results from an imbalance between energy intake and energy expenditure, which emphasizes the importance of deciphering the mechanisms behind energy balance regulation to understand its physiopathology. The control of energy balance is assured by brain systems/circuits capable of generating adequate ingestive and thermogenic responses to maintain the stability of energy reserves, which implies a proper integration of the homeostatic signals that inform about the status of the energy stores. In this article, we overview the organization and functionality of key neuronal circuits or pathways involved in the control of food intake and energy expenditure. We review the role of the corticolimbic (executive and reward) and autonomic systems that integrate their activities to regulate energy balance. We also describe the mechanisms and pathways whereby homeostatic sensing is achieved in response to variations of homeostatic hormones, such as leptin, insulin, and ghrelin, while putting some emphasis on the prominent importance of the mechanistic target of the rapamycin signaling pathway in coordinating the homeostatic sensing process.

Fat and lean tissue accretion in relation to reward motivation in children

'Reward sensitivity' explains inter-individual differences in the motivation to obtain rewards when reward cues are perceived. This psychobiological trait has been linked to higher consumption of palatable food when exposed to palatable food cues. The current study aims to examine if reward sensitivity explains differences in patterns of fat and lean tissue accretion over time in children. A longitudinal observational study with measurement waves in 2011 (baseline), 2012, 2013, and 2015 was conducted. The sample was a population-based Flemish cohort of children (n = 446, 50% boys and 5.5-12 years at baseline; 38.8% of the baseline sample also participated in 2015). Baseline reward sensitivity of the children was assessed by parent ratings on the Drive subscale of the Behavioral Inhibition System/Behavioral Approach System scales. Age- and sex-independent Fat and Lean Mass Index z-scores (zFMI and zLMI respectively) were computed for each study wave based on air-displacement plethysmography. In girls, but not boys, reward sensitivity was positively associated with the baseline zFMI and zLMI (95% confidence intervals of unstandardized estimates: 0.01 to 0.11 and 0.01 to 0.10 respectively, P values 0.01 and 0.02 respectively). Further, reward sensitivity explained 14.8% and 11.6% of the change in girls' zFMI and zLMI respectively over four years: the zFMI and zLMI increased and decreased respectively in high reward sensitive girls (95% confidence intervals of unstandardized estimates: 0.01 to 0.11 and -0.12 to -0.01 respectively, P values 0.01 and 0.02 respectively). Hence, girls high in reward sensitivity had significantly higher adiposity gain over four years parallel with lower increase in lean mass than was expected on the basis of their age and height. These results may help to identify appropriate targets for interventions for obesity prevention.