Neuroanatomical Correlates of Binge-Eating Behavior: At the Roots of Unstoppable Eating

Reduction of drive for thinness and body dissatisfaction in people with self-reported dysregulated eating behaviors after intermittent theta burst stimulation (iTBS) of the left dorsolateral prefrontal cortex

Aim

This study aimed to explore the effect of intermittent theta burst stimulation (iTBS) of the right and left dorsolateral prefrontal cortex (DLPFC) in people with self-reported dysregulated eating behaviors but without a diagnosis of eating disorders (EDs).

Methods

Participants were randomly divided into two equivalent groups according to the side (right or left) of the hemisphere to be stimulated and they were tested before and after a single iTBS session. Outcome measurements were scores on self-report questionnaires assessing psychological dimensions related to eating behaviors (EDI-3), anxiety (STAI-Y), and tonic electrodermal activity.

Results

The iTBS interfered with both psychological and neurophysiological measures. Significant variations of physiological arousal after iTBS of both the right and left DLPFC were witnessed by increased mean amplitude of non-specific skin conductance responses. With regard to the psychological measures, the iTBS on the left DLPFC significantly reduced the scores of the EDI-3 subscales drive for thinness and body dissatisfaction. Interestingly, these two scales are two of the three EDI-3 clinic scales (drive for thinness, body dissatisfaction, and bulimia) used as specific markers to assess the onset and/or maintenance of eating disorders.

Conclusion

Our results show that the left DLPFC iTBS has an impact on the psychological dimensions that are risk factors for the onset of eating disorders, suggesting that an altered hemispheric asymmetry similar to that encountered in clinical populations is present in normal subjects even in the absence of clinical symptoms.

The neurobiological reward system and binge eating: A critical systematic review of neuroimaging studies

OBJECTIVE

Changes in reward processing are hypothesized to play a role in the onset and maintenance of binge eating (BE). However, despite an increasing number of studies investigating the neurobiological reward system in individuals who binge eat, no comprehensive systematic review exists on this topic. Therefore, this review has the following objectives: (1) identify structural and functional changes in the brain reward system, either during rest or while performing a task; and (2) formulate directions for future research.

METHODS

A search was conducted of articles published until March 31, 2022. Neuroimaging studies were eligible if they wanted to study the reward system and included a group of individuals who binge eat together with a comparator group. Their results were summarized in a narrative synthesis.

RESULTS

A total of 58 articles were included. At rest, individuals who binge eat displayed a lower striatal dopamine release, a change in the volume of the striatum, frontal cortex, and insula, as well as a lower frontostriatal connectivity. While performing a task, there was a higher activity of the brain reward system when anticipating or receiving food, more model-free reinforcement learning, and more habitual behavior. Most studies only included one patient group, used general reward-related measures, and did not evaluate the impact of comorbidities, illness duration, race, or sex.

DISCUSSION

Confirming previous hypotheses, this review finds structural and functional changes in the neurobiological reward system in BE. Future studies should compare disorders, use measures that are specific to BE, and investigate the impact of confounding factors.

PUBLIC SIGNIFICANCE STATEMENT

This systematic review finds that individuals who binge eat display structural and functional changes in the brain reward system. These changes could be related to a higher sensitivity to food, relying more on previous experiences when making decisions, and more habitual behavior. Future studies should use a task that is specific to binge eating, look across different patient groups, and investigate the impact of comorbidities, illness duration, race, and sex.

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSIONS

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