The neural underpinnings of eating behavior have yet to be elucidated. Neuroimaging has mainly examined the direct correlates of eating behavior, an approach which has been helpful in discovering areas of the brain involved in the direct response to ingestion, but less so in determining general pattern of brain function associated with obesity. Few investigators have used resting state fMRI (RS-fMRI) to elucidate neural functioning associated with obesity and none in conjunction with direct assessments of eating behavior.
102 adults recruited from the community were fasted overnight and assessed for BMI with a Detecto triple beam scale and stadiometer. They had a multi-item breakfast with instructions to “eat as much as you like” for 15 minutes, after which the micro and macronutrient content they consumed was assessed. They then were scanned with a 3T Siemens Magnetomincluding a 10 minute RS-fMRI. Imaging was pre-processed and analyzed using AFNI and FSL commands and resting state functional connectivity was analyzed in conjunction with seed regions selected for relevance to salience (insula, Orbitofrontal cortex), reward (Nucleus Accumbens) and executive function (Inferior frontal gyrus) and regressed against both BMI and proportion of calories from fat ingested during the meal. Results were thresholded at a z score of 2.3 and a p of 0.05 for clusters and then again using a threshold free cluster enhancement technique.
At the highest level of thresholding seed regions of interest in left and right insula demonstrated connectivity with regions in inferior temporal and lingual gyrus respectively.
While lower levels of thresholding suggested connectivity between nucleus accumbens and sensory motor gyrus with BMI the highest level showed connectivity to insula to be the most robust suggesting the importance of the insula in coordinating salience valuation and directing eating behavior, these findings are concordant with those in addiction and smoking behavior.