Embodiment of underweight and normal-weight avatars affects bodily self-representations in anorexia nervosa

Body image distortion (BID) is a crucial aspect of anorexia nervosa (AN), leading to body overestimation, dissatisfaction, and low self-esteem. BID significantly influences the onset, maintenance, and relapse of the pathology. We assessed whether a Full Body Illusion (FBI) using under and normal-weight avatars' bodies affects perceptual body image and body schema estimations in both individuals with anorexia nervosa (AN) and healthy controls (HC). After each embodiment procedure, we asked participants to estimate the width of their hips (Perceptual Body Image Task) and the minimum aperture width of a virtual door necessary to pass through it (Body Schema Task). Additionally, we asked participants to rate the avatars in terms of self-similarity, attractiveness, and implicit disgust (i.e., pleasant/unpleasant body odour). Whereas participants with AN (N = 26) showed changes in body schema estimations after embodying the normal-weight avatar, no changes were found in HC (N = 25), highlighting increased bodily self-plasticity in AN. Notably, individuals with AN rated the normal weight avatar as the most similar to their real body, which was also considered the least attractive and the most repulsive. These ratings correlated with BID severity. Furthermore, at the explicit level, all participants reported feeling thinner than usual after embodying the underweight avatar. Overall, our findings suggest that BID in AN engages multiple sensory channels (from visual to olfactory) and components (from perceptual to affective), offering potential targets for innovative non-invasive treatments aimed at modifying flexible aspects of body representation.