The Effect of a Virtual-Reality Full-Body Illusion on Body Representation in Obesity

Abstract

Background. The effective illusory ownership over an artificial body in modulating body representations in healthy and eating disorders population has been repeatedly reported in recent literature. In this study, we extended this research in the field of obesity: specifically, we investigated whether ownership over a virtual body with a skinny abdomen might be successfully experienced by participants affected by obesity. Methods. Fifteen participants with obesity and fifteen healthy-weight participants took part at this study in which the VR-Full-Body Illusion was adopted. The strength of illusion was investigated through the traditional Embodiment Questionnaire, while changes in bodily experience were measured through a body size estimation task. Results. Participants with obesity as well as healthy-weight participants reported to experience the illusion. About the body size estimation task, both groups reported changes only in the estimation of the abdomen’s circumference after the experimental condition, in absence of any another difference. Discussion. Participants with obesity reported to experience the illusion over a skinny avatar, but the modulation of the bodily experience seems controversial. Future lines of research exploiting this technique for modulating body representations in obesity, specifically in terms of potential therapeutic use, were discussed.

Gulliver’s virtual travels: active embodiment in extreme body sizes for modulating our body representations

“…Longo and colleagues (Sadibolova et al 2019 ) confirmed the presence of large body size distortions also in normal-weight population, and interestingly, they emphasized that the largest underestimation was found for the volume of the torso. More recently, we reported that healthy participants perceived their shoulders larger after they have embodied a skinny avatar (Scarpina et al 2019 ). These opposite results might suggest that bodily illusions affect body parts representations differently; however, it still an open question which body parts and in what circumstances can be misperceived, and in which direction.…”

“…Regarding the Embodiment Questionnaire (Serino et al 2016 ; Scarpina et al 2019 ), participants reported to have experienced a solid illusion in terms of body ownership and agency, independently from the experimental condition. Participants perceived the avatar as their own actual body, as well as the avatars’ movements as their own movements, despite its size.…”

“…The first experimental condition (“Active Embodiment in a normal-sized body”) was maintained as the first one for all participants, while the other two experimental conditions were within-participants randomized. After each virtual experience, all participants were asked to complete the body size estimation task (Serino et al 2016 ; Scarpina et al 2019 , Keizer et al 2011 ) and to complete the adapted version of the Embodiment Questionnaire (Serino et al 2016 ; Scarpina et al 2019 ).…”

“…Using a virtual full-body illusion (i.e. individuals experience the feeling of being the owner of another fake body thanks to the delivery of a synchronous multisensory stimulation on the actual body and its fake virtual counterpart), our group demonstrated that the embodiment over a virtual avatar with a thin body led to a significant shrinkage of subjects’ body representations (Serino et al 2016 ; Scarpina et al 2019 ).…”

“…Our main aim was to test whether this illusionary action-driven experience changed perceptual judgement of bodily dimensions. Thus, at the end of each embodied navigation, participants were asked to estimate the dimension of three different body parts (shoulders, abdomen and hips) and their height (Serino et al 2016 ; Scarpina et al 2019 , Keizer et al 2011 ).…”