An fMRI study of proneness to overeating: Effects of hunger status, food stimuli, and level of restrain

Eating regulation research has shown that normal weight restrained eaters eat more following a preload than they do in the absence of a preload, a paradoxical result termed "counterregulatory eating." Research has indicated that the overeating tendencies in restrained eaters are not due to dieting behavior. Using fMRI, a pilot study found interesting differences in the brain activation of normal weight restrained eaters compared to unrestrained eaters in response to highly palatable food stimuli in both a fasted and fed state. The current study aimed to replicate the findings of the preliminary study with a larger number of subjects. We investigated brain activation of normal weight restrained (N = 9) and unrestrained eaters (N = 10) when in a fasted and fed state and when viewing pictures of highly and moderately palatable food. Unrestrained eaters showed bilateral activation to high palatability food stimuli when fasted, in areas associated with hunger, memory, and motivation. In the same state restrained showed activation only in the right cerebellum, which has previously been implicated in low-level processing of appetitive stimuli. While viewing high palatability foods in a fed state, restrained eaters showed activation again in the right cerebellum, as well as the left orbitofrontal cortex, dorsolateral prefrontal cortex, and left insular cortex. The left orbitofrontal and dorsolateral prefrontal cortices have been implicated in goal oriented planning, expectation of reward, and goal defined behavior. The insular cortex has been shown in previous research to play a role in food craving and desire. Activation for unrestrained eaters when fed was found in areas related to satiation and memory. These findings support the findings in the preliminary study and provide new insight into the mechanism underlying counterregulatory eating in restrained eaters. Both studies suggest that normal weight restrained and unrestrained eaters may show different eating regulation patterns because restrained eaters are less hungry than unrestrained eaters when fasted and find palatable food more appealing than unrestrained eaters when fed.