Characterizing body Image distortion and bodily-self plasticity in anorexia nervosa via immersive virtual reality

Body Image Distortion (BID) is a core symptom of Anorexia Nervosa and it affects both the perceptive (body overestimation) and the cognitive-emotional (body dissatisfaction) components of body image. Recent experimental evidence shows that Immersive Virtual reality (IVR) and Full Body Illusion (FBI) can alter the BID in anorexic patients (AN). We created avatars reconstructing participants’ bodies, alongside a series of fatter and slimmer avatars. We measured participants’ body overestimation and dissatisfaction by asking the participants (20 AN, 20 age-matched controls, all females) to choose the avatars that best resembled their real and ideal body. FBI was induced via a/synchronous visuo-tactile stimulation applied to three avatars of different sizes (the chosen avatar, one fatter and one thinner than the chosen one) observed from the first-person perspective. We recorded real and ideal body size ratings before and after the FBI, together with participants’ emotional state and explicit (embodiment questionnaire) and implicit (body temperature) measures of embodiment. Compared to controls, AN chose fatter avatars in the perceived body task and thinner avatars in the ideal body task. While AN and controls showed the same explicit level of embodiment regardless of the avatars’ size, AN showed lower body temperature after FBI, indicating a stronger illusion and greater body image malleability. Interestingly, AN reported more negative emotions after embodying the fatter avatar and this correlates with symptoms severity. Considering these results, we think that FBI induced in a IVR setting might represent a powerful tool in the diagnosis and treatment of BID in anorexia.