Characterizing Body Image Distortion and its Plasticity in Anorexia Nervosa

Despite being underweight, anorexic patients overestimate their body size and report a high level of dissat-isfaction towards their appearance. This condition is known as Body Image Distortion (BID) and it comprises of a perceptive component and a cognitive-emotional component. Recent experimental evidence shows that embodiment illusions in virtual reality can alter anorexic pa-tients’ distorted body perception. In the present research, we built avatars resembling participants’ bodies, alongside a series of avatars de-picting realistic weight gain and loss. Participants (20 anorexics, 20 age-matched controls, all females) chose the avatar that best resembled their body, thus providing us with a measure of body size estimation. Embodiment illusion was induced via a/synchronous visuo-tactile stimulation applied to 3 avatars of differ-ent sizes (the chosen avatar, one thinner and one fatter) seen from the first-person perspective. We rec-orded ratings of ideal and real body size before and after the embodiment, together with participants’ emotional state and explicit (embodiment questionnaire) and implicit (body temperature) measures of em-bodiment. Results show that anorexic patients reported a perceptual overestimation and a cognitive-emotional body distortion. Moreover, they implicitly experienced a stronger embodiment illusion, which implies greater body image malleability compared to controls, as indexed by lower body temperature following the illusion. Interestingly, anorexics reported more negative emotions after embodying the biggest of the 3 avatars and this correlates with symptoms severity. Considering that our procedure succeeded in measuring both components of BID, we think that bodily illu-sions might represent a powerful tool for diagnosing and potentially treating BID in anorexia.