BackgroundThe regulation of energy intake is a complex process involving the integration of homeostatic signals and both internal and external sensory inputs. The objective of this study was to examine the effects of short-term overfeeding on the neuronal response to food-related visual stimuli in individuals prone and resistant to weight gain.Methodology/Principal Findings22 thin and 19 reduced-obese (RO) individuals were studied. Functional magnetic resonance imaging (fMRI) was performed in the fasted state after two days of eucaloric energy intake and after two days of 30% overfeeding in a counterbalanced design. fMRI was performed while subjects viewed images of foods of high hedonic value and neutral non-food objects. In the eucaloric state, food as compared to non-food images elicited significantly greater activation of insula and inferior visual cortex in thin as compared to RO individuals. Two days of overfeeding led to significant attenuation of not only insula and visual cortex responses but also of hypothalamus response in thin as compared to RO individuals.Conclusions/SignificanceThese findings emphasize the important role of food-related visual cues in ingestive behavior and suggest that there are important phenotypic differences in the interactions between external visual sensory inputs, energy balance status, and brain regions involved in the regulation of energy intake. Furthermore, alterations in the neuronal response to food cues may relate to the propensity to gain weight.

Sex-based differences in food intake related behaviors have been observed previously. The objective of this study was to examine sex-based differences in the behavioral and neuronal responses to food. 22 women and 21 men were studied. After 6 days of controlled eucaloric feeding, ad libitum energy intake (EI) was measured for three days. Appetite ratings using visual analog scales were obtained before and after each meal. Functional magnetic resonance imaging was performed in the overnight fasted state on the last day of eucaloric feeding while subjects were presented visual stimuli of food and neutral nonfood objects. While hunger and prospective consumption were not different between sexes, women had higher post-meal satiety ratings and dietary restraint than men. Images of hedonic foods resulted in significantly greater activation of lateral and dorsolateral prefrontal cortex (DLPFC) and parietal cortex in women as compared to men. No brain regions were more activated in men as compared to women. Men increased their EI during the ad libitum diet phase. While measures of appetite or feeding behaviors did not correlate with either neuronal activation or subsequent EI, DLPFC activation in response to hedonic foods was negatively correlated with EI. In summary, greater prefrontal neuronal responses to food cues in women may suggest increased cognitive processing related to executive function, such as planning, guidance or evaluation of behavior. Finally, increased DLPFC activation, perhaps relating to inhibitory cognitive control in response to food cues may be a better predictor of food intake than behavioral measures.