Stress-induced alterations in HPA-axis reactivity and mesolimbic reward activation in individuals with emotional eating

Altered neural representation of olfactory food reward in the nucleus accumbens after acute stress

Acute stress impairs reward processing. The nucleus accumbens (NAcc) plays an important role in the processing of primary rewards such as food. The present study investigates how acute stress affects the olfactory food reward processing in the NAcc using the representational similarity analysis. Forty-eight participants underwent an olfactory fMRI session following either an acute psychosocial stress (N = 24; stress group) or a control (N = 24; control group). Brain activation was recorded during the anticipatory and the perceptual phases of high-calorie food, low-calorie food, and non-food odor stimuli. Compared to the control group, the stress group rated the high-calorie food odor as significantly more pleasant (p = 0.005). In the NAcc, acute stress significantly reduced the dissimilarity of food and non-food odors in the perceptual phase (p = 0.027) and marginally reduced the dissimilarity of high- and low-calorie foods in the anticipatory phase (p = 0.095). Significant negative correlations were observed between the level of NAcc representational differentiation for high- and low-calorie food odors during perception and the difference in pleasantness ratings between high- and low-calorie food odors (r = -0.40, p = 0.005). These findings suggest that acute stress may impair participants' ability to discriminate between olfactory food rewards, leading individuals to seek out more palatable foods in stressful situations in order to maintain positive emotions.

Higher morning cortisol is associated with lower intuitive eating in midlife women

BACKGROUND

Stress is associated with negative health outcomes in adults, including increased adiposity. Eating behaviors to cope with stress can have a negative effect on adiposity. There is limited research on positive eating behaviors, such as intuitive eating (IE), and their relationship to stress and adiposity. Thus, this study aimed to examine the association between stress and adiposity and to assess whether IE is a mediator of that pathway.

METHODS

Data were analyzed from a cross-sectional study of 114 women between 40-64 years of age. Participants completed in-person visits and self-reported questionnaires, including the Intuitive Eating Scale and Perceived Stress Scale. Adiposity was assessed using dual energy x-ray absorptiometry. Measurements included total body fat percentage and android/gynoid (AG) ratio as a measure of abdominal adiposity. Participants provided ten salivary cortisol samples over two days, collected upon waking, 30-, 45-, and 60-minutes after waking, and prior to bed. Several methods were used to characterize cortisol secretion and exposure, including the diurnal cortisol slope and the cortisol area under the curve with respect to ground (AUCg). Linear regression was used to assess the associations between perceived stress and IE and between features of diurnal cortisol and IE. Mediation models were tested to examine the indirect effects of IE on the relationship between perceived stress and adiposity and to test the indirect effects of IE on the relationship between cortisol measures and adiposity.

RESULTS

Linear regression analyses indicated that higher cortisol AUCg was associated with lower scores on the eating for physical reasons subscale (β: -0.01, p = 0.008). After adjusting for covariates, neither higher perceived stress nor diurnal cortisol were associated with intuitive eating. There was no evidence of mediation of the association of stress on adiposity through IE.

CONCLUSION

Our findings demonstrate a relationship between higher overall morning cortisol and lower scores on the eating for physical reasons subscale of the Intuitive Eating Scale. Future research should seek to understand how intuitive eating may be used as a technique for individuals who engage in emotional eating to cope with stress, and to prevent excess adiposity resulting from stress in midlife women.

Delay Discounting and the Income-Food Insecurity-Obesity Paradox in Mothers

Food insecurity, defined as unpredictable access to food that may not meet a person's nutritional needs, is paradoxically associated with higher BMI (kg/m2) and obesity. Research has shown delay discounting, a behavioral economic measure of the preference for immediate rather than delayed rewards, is related to higher BMI, and moderates the relationship between income and food insecurity. Based on this research, we used regression models to test whether delay discounting, consideration of future consequences, and perceived stress were atemporal mediators of the food insecurity-BMI relation in 313 mothers, controlling for demographic variables. A secondary aim was to replicate the finding that delay discounting moderates the relationship between low income and high food insecurity. Results showed that low income was associated with higher food insecurity, and higher food insecurity was associated with higher BMI. Delay discounting was the only variable that was indirectly related to both paths of the food-insecurity-BMI relation. Delay discounting accounted for 22.2% of the variance in the low-income-food insecurity-obesity relation, and the total model accounted for 38.0% of the variance. The relation between low income and food insecurity was moderated by delay discounting. These data suggest that delay discounting is a potential mediator of the relationship between food insecurity and high BMI, which suggests reducing discounting in the future could be a novel target to reduce food insecurity and help people with food insecurity to reduce their excess body weight. Trial Registration. This trial is registered with NCT02873715.

The influence of stress on the neural underpinnings of disinhibited eating: a systematic review and future directions for research

Disinhibited eating involves overconsumption and loss of control over food intake, and underpins many health conditions, including obesity and binge-eating related disorders. Stress has been implicated in the development and maintenance of disinhibited eating behaviours, but the mechanisms underlying this relationship are unclear. In this systematic review, we examined how the impact of stress on the neurobiological substrates of food-related reward sensitivity, interoception and cognitive control explains its role in disinhibited eating behaviours. We synthesised the findings of functional magnetic resonance imaging studies including acute and/or chronic stress exposures in participants with disinhibited eating. A systematic search of existing literature conducted in alignment with the PRISMA guidelines identified seven studies investigating neural impacts of stress in people with disinhibited eating. Five studies used food-cue reactivity tasks, one study used a social evaluation task, and one used an instrumental learning task to probe reward, interoception and control circuitry. Acute stress was associated with deactivation of regions in the prefrontal cortex implicated in cognitive control and the hippocampus. However, there were mixed findings regarding differences in reward-related circuitry. In the study using a social task, acute stress associated with deactivation of prefrontal cognitive control regions in response to negative social evaluation. In contrast, chronic stress was associated with both deactivation of reward and prefrontal regions when viewing palatable food-cues. Given the small number of identified publications and notable heterogeneity in study designs, we propose several recommendations to strengthen future research in this emerging field.

Association between anxiety and metabolic syndrome: An updated systematic review and meta-analysis

OBJECTIVE

Previous studies have demonstrated an association between anxiety and metabolic syndrome (MetS). However, the association is still controversial. This updated meta-analysis aimed to reanalyze the association between anxiety and MetS.

METHODS

We comprehensively searched PubMed, Embase and Web of Science for all related studies published before January 23, 2023. Observational studies that informed effect size with 95% confidence interval (CI) for the association between anxiety and MetS were included. According to heterogeneity between studies, fixed or random effects models were applied to calculate the pooled effect size. Publication bias was examined by funnel plots.

RESULTS

The research included 24 cross-sectional studies: 20 studies used MetS as the dependent variable with a pooled OR of 1.07 (95% CI: 1.01-1.13) and four studies used anxiety as the dependent variable with a pooled OR of 1.14 (95% CI: 1.07-1.23). Three cohort studies were found: two studies detected the association of baseline anxiety with the risk of MetS, one of the studies demonstrated a significant association, but a similar result was not found in another study; one study showed no significant association between baseline MetS and the risk of anxiety.

CONCLUSION

Cross-sectional studies indicated an association between anxiety and MetS. The results from cohort studies are still inconsistent and limited. More large-scale prospective studies are needed to further reveal the causal relationship of anxiety with MetS.

The perceived role of food and eating among turkish women with obesity: A qualitative analysis

The studies show the link between Body Mass Index (BMI) and higher food responsiveness despite negative physical, social, and psychological outcomes. The descriptive studies examining what makes individuals with higher BMI values more likely to respond to food are limited, while there is none in the Turkish sample. This study aims to understand the subjective relationship of women with obesity/overweight related to food in Turkish culture. Turkish adult women (aged 22-54) who have BMI higher than 25 (overweight/obesity) participated in semi-structured interviews focusing on how they relate to food and obesity. Participants were reached through Ankara Etlik Zübeyde Hanım Obstetrics and Gynecology Hospital Obesity outpatient service. Audio-recorded interviews were analyzed predominantly inductively by thematic analysis principles. Analysis of these interviews reflected three main themes: (1) the act of eating: "I don't know why I eat when I'm full", (2) being overweight: "I am the kind of person who constantly tries to lose weight", and (3) sources of distress. The results indicated the dynamic relationship between the desire to eat, chronic stress, perceived unavailability of close ones, and low sense of self-worth among adult women with obesity/overweight. The other indication is the effect of culture in shaping the relationship dynamics, the sources of distress, and the eating patterns in developing and maintaining obesity.

Chronic Restraint Stress Decreases the Excitability of Hypothalamic POMC Neuron and Increases Food Intake

Stress activates the hypothalamic-pituitary-adrenal system, and induces the release of glucocorticoids, stress hormones, into circulation. Many studies have shown that stress affects feeding behavior, however, the underlying circuitry and molecular mechanisms are not fully understood. The balance between orexigenic (simulating appetite) and anorexigenic (loss of appetite) signals reciprocally modulate feeding behavior. It is suggested that proopiomelanocortin (POMC) and neuropeptide Y (NPY) neurons in the arcuate nucleus (ARC) of the hypothalamus are the first-order neurons that respond to the circulating signals of hunger and satiety. Here, we examined a chronic restraint stress model and observed an increase in food intake, which was not correlated with anhedonia. We investigated whether stress affects the properties of POMC and NPY neurons and found that chronic restraint stress reduced the excitatory inputs onto POMC neurons and increased the action potential threshold. Therefore, our study suggests that chronic stress modulates the intrinsic excitability and excitatory inputs in POMC neurons, leading to changes in feeding behavior.