Objective Obesity and binge eating disorder have been suggested to be associated with impulsivity and disruption on the cortico-striatal brain network. Here we aimed to examine global network structure in resting state brain of obese subjects with and without binge eating disorder (BED) compared to healthy controls.

Method Multi-echo resting state BOLD fMRI scans were taken from 42 obese subjects (including 21 patients with BED; BMI >30) and 42 age-matched healthy controls in normal range of BMI for 10 minutes using 3T Siemens MRI scanner. Non-BOLD noises in the resting stat fMRI data was removed using Multi-Echo Independent Component Analysis (ME-ICA) pipeline, and functional connectivity in 90 ROIs of the Anatomical Automatic Labeling template was estimated using zero-lag cross-correlation. The functional connectivity weights were binarized with the density threshold (5–30%) and complex network properties such as local and global efficiency, assortativity and modularity was computed.

Results Both obese subjects with and without binge eating disorder were significantly different from healthy controls in normal BMI ranges in complex brain network properties, but did not differ from each other. Both obsese groups are collapsed in the subsequent analysis and compared to healthy controls. Obese subjects were significantly reduced local and global efficiency compared to healthy controls, implying disrupted small-world network properties in brain networks of obese subjects. Modularity of resting state brain network was also decreased in obese subjects. Among regions of a priori interests, bilateral putamen exhibited reduced functional connections (degree) and local efficiency in obese subjects. Local efficiency was also deceased in bilateral insula in low density network (<15% density). Right caudate and putamen showed increased betweeness-centrality in obese subjects, implying their augmented role as connecting hubs in the resting state brain network. In Region-to-Region functional connectivity, obese subjects exhibited reduced functional connectivity in the putamen, pallidum, thalamus and caudate.

Conclusion Small-world and modular structure of resting state brain network was disrupted in obese subjects compared to healthy subjects, suggesting less functional segregation and integration in their brains. Disrupted cortico-striatal network is implicated in these global change of resting state brain in obese subjects.