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

Binge eating disorder (BED) is characterized by repeated episodes of binge eating accompanied by a loss of control. Although the neurobiological underpinnings of binge eating (BE) episodes are not fully understood, 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 = 0.024), but not effort exertion (F34,21 = 1.13, pboot = 0.30). 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.