Previous studies have reported that obesity and eating disorders are more prevalent in women than men. Eating behaviour patterns differ in men and in women, they are affected by motivational state (fed versus fasted), and there are also neural differences in cognitive, emotional and reward processing. Several structural brain differences between obese and lean persons have been identified, and cerebral white matter changes have been found related to elevated body weight in men compared with women. This study aimed to investigate gender-based differences in neural activation using functional magnetic resonance imaging (fMRI) in response to high energy-dense (high-ED) versus low-ED visual and auditory food cues in both fed and fasted states. 17 men and 14 women with similar body mass index and age were exposed to high-ED food (> 3,5 kcal/g i.e. pizza), low-ED food (< 1 kcal/g i.e. raw vegetables), and non-food stimuli in both visual (photos) and auditory (spoken words) modalities during fMRI. The experiment was repeated on 2 non-consecutive days, once in fasted state and once in fed state. When fed, all participants showed higher neural activation for high-ED than for low-ED food cues in primary and association sensory cortices. In the fasted state, the same areas showed higher neural activation (as well as brainstem, cognitive and reward processing areas) in response to high versus low-ED food cues. In response to visual high-ED (versus low-ED) food cues, when fed, men showed greater activation in the left fusiform gyrus, while women had greater activation than men in the right dorsal anterior cingulate cortex. When fasted, men showed greater activation in right inferior parietal lobule and women had greater activation in the bilateral caudate nucleus and right temporal-occipital area. In response to auditory high-ED (versus low-ED) food cues, when fed, men showed greater activation in bilateral supplementary motor areas and right precentral gyrus than women. When fasted, women showed greater activation in right parahippocampal gyrus.
These results showed that in response to high versus low-ED foods in the fed state, obese men had greater activation than women in brain areas associated with motor execution and planning, while women showed greater activation in regions related to cognitive and emotional processing. When fasted, obese men had greater activation in visual and attention regions, while obese women showed greater activation in affective and reward-related processing regions (i.e. caudate nucleus, which is associated with craving).
The greater affective neural processing in obese women could be a contributing factor for the higher prevalence of obesity in women and this finding may improve our understanding of gender specific differences among obese individuals in eating behaviour.