Obesity is associated with greater variability of reward signals in the nucleus accumbens

Background Binge eating disorder (BED) is characterized by repeated episodes of binge eating accompanied by a loss of control. Although it remains unknown which factors drive binge eating (BE) episodes, there are indications that variability in nucleus accumbens (NAcc) responses could lead to increased variability in food intake.

Here, we assessed whether BED is associated with higher intra-individual variability in behavioral and neuroimaging indices of reward responses. To this end, patients with BED (n = 35, MBMI = 33.2 kg/m2 ± 6.8), participants with subsyndromal BED (n = 21, MBMI = 29.0 kg/m2 ± 7.2), and individuals without symptoms of binge eating (n = 23, MBMI = 32.3 kg/m2 ± 6.5) completed an effort allocation task with concurrent functional magnetic resonance imaging.

In line with our hypothesis, we found that patients with BED had higher variability in subjective wanting ratings of food (F34,21 =1.48, pboot = .024), but not effort exertion (F34,21 = 1.13, pboot = .30). Crucially, trial-by-trial variability in NAcc responses during the presentation of cues was associated with a higher BMI (b=0.11, 95%CI [0.03, 0.19], BF10=11.1) and disinhibited eating (b=0.19, 95%CI [0.01, 0.36], BF10=4.0) across groups, whereas NAcc variability was only marginally elevated in patients with BED (b=0.12, 95%CI [−0.04, 0.29], BF10=1.2, P>0|data = 88%).

Our results support the idea that BMI and disinhibited eating are associated with more variable NAcc responses, which may contribute to the symptoms of BED. However, this association is only weakly indicative of clinical severity of BED. Competing Interest Statement The overarching study in which this research took place included a research cooperation with Boehringer Ingelheim to analyze ghrelin levels. These data are not part of the current manuscript. Funding Statement The study was supported by the Else Kroener-Fresenius Stiftung grant 2017_A67, and DFG KR 4555/7-1, KR 4555/9-1, and KR 4555/10-1. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the institutional review board of the University of Tuebingen (3939/2017BO2) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability Trial-based data will be shared upon reasonable request to the authors