Effects of overfeeding on the neuronal response to visual food cues

Background: The regulation of energy intake is a complex process involving the integration of homeostatic signals and both internal and external sensory inputs. Environmental visual cues are one of the first and primary inputs signaling the potential availability of food. Objective: We examined the effects of short-term overfeeding on the neuronal responses to food-related visual stimuli in thin individuals. Design: Twenty-five thin individuals (13 women, 12 men) were studied. Functional magnetic resonance imaging (fMRI) was performed after 2 days of eucaloric energy intake and after 2 days of 30% overfeeding in a counterbalanced design. fMRI was performed while the subjects were presented with visual stimuli in 3 different categories: neutral control objects, foods of neutral hedonic value, and foods of high hedonic value. Measures of appetite were obtained by using visual analogue scales before and after meals. Results: In the eucaloric state, pictures of foods of high hedonic value elicited greater activation of neuronal regions than did neutrally rated foods, which is consistent with visual processing and attention (inferior temporal visual cortex, posterior parietal cortex, premotor cortex, and hippocampus) and with activation of the hypothalamus. Two days of overfeeding led to significant attenuation of these responses. Overfeeding also resulted in reduced hunger ratings and increased satiety ratings. Conclusion: These findings emphasize the important role of external food-related visual cues and suggest that there are interactions between external visual sensory inputs, energy balance status, and brain regions important in the homeostatic regulation of energy intake.