Obesity is associated with reduced sensitivity to stimulus rewarding value, but unaltered effects of fasting and contextual modulation during action prediction

Previous studies have shown that our perception of others' actions is influenced by both the reward value of target objects and our internal motivational state. In the present study, we investigated how the energy content of the target object and the physiological state of hunger influence the prediction of food-oriented actions in people with a healthy weight or obesity. Thirty-one participants with normal-weight and 31 participants with obesity performed a social perception task in which, under a fasting or a satiety state, they had to predict the intention of actions directed to high- or low-energy food objects in the context of a breakfast table that could suggest congruent or incongruent actions compared to action kinematics. The results showed that action prediction performance was greater: 1) for high-compared to low-energy food objects in the group with healthy weight but not in the group with obesity, with lower sensitivity to the energy content of the target object in individuals with more weight; 2) under a fasting compared to a satiety state in both groups; 3) for actions embedded in congruent compared to incongruent contexts when directed to high- but not low-energy food objects, independently of group and hunger state. The findings document an altered sensitivity to the reward value of action stimuli in people with obesity, despite a conserved sensitivity to hunger and contextual modulation. This supports a reduced sensitivity to the reward value of food stimuli in people with obesity pointing at a dysfunctional reward system during action perception. Interestingly, being under a food deprivation state comparably boosted performance in both groups, providing evidence that fasting may sharpen senses independently from individual weight.