THURSDAY, Sept. 22 (HealthDay News) -- Mild hypoglycemia activates limbic-striatal brain regions in response to food cues resulting in a increased desire for high-calorie food, whereas higher circulating glucose levels predict increased medial prefrontal cortex activation, a response which is absent in obese individuals, according to a study published online Sept. 19 in the Journal of Clinical Investigation.
Kathleen A. Page, M.D., from the Yale University School of Medicine in New Haven, Conn., and colleagues investigated whether circulating levels of glucose influenced brain regions regulating the motivation to consume high-calorie foods. A total of 14 healthy (nine nonobese and five obese) and seven control subjects underwent functional magnetic resonance imaging (fMRI) two hours after ingesting a standardized lunch. During the fMRI study participants underwent a stepped hyperinsulinemic euglycemic-hypoglycemic clamp and viewed high-calorie food, low-calorie food, and non-food images. Control participants underwent the same protocol but with a hyperinsulinemic-euglycemic clamp. Behavioral measures of interest in food and hunger ratings were assessed at the beginning and end of each phase.
The investigators found that mild hypoglycemia activated the limbic-striatal regions of the brain preferentially, generating a greater desire for high calorie food in response to food cues. The brain's medial prefrontal cortex was preferentially activated during the euglycemic state and resulted in less interest in food stimuli. Greater medial prefrontal cortex activation was predicted by higher circulating glucose levels but this response was absent in obese patients.
"These findings demonstrate that circulating glucose modulates neural stimulatory and inhibitory control over food motivation and suggest that this glucose-linked restraining influence is lost in obesity," the authors write.
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