Impact of an overweight body representation in virtual reality on locomotion in a motor imagery task.

Virtual reality immersion enables a person to embody avatars that strongly deviate from his/her biological body. Interestingly, the person's expectations about the embodied avatar lead to congruous behavior, phenomenon referred to as the Proteus effect. The objective of the present study was to investigate, in virtual reality, the relationship between body-shape representation and expected physical abilities in a locomotor imagery task, in the context of overweight avatar embodiment. Given the negative stereotypes concerning overweight people's physical abilities, we expected overweight avatar embodiment to have a negative impact on performance in the locomotor imagery task. Thirty-five healthy-weight participants, with a body mass index between 16.5 and 30 at the time of the experiment or in the past, embodied both a healthy-weight avatar and an overweight avatar on two different experimental sessions while performing the imagery task (walking four different distances on two different slopes). In accordance with our hypothesis, participants took longer to perform the locomotor imagery task when embodying an overweight avatar than when embodying a healthy-weight one (the "avatar effect")-especially so when the distance to be covered was long. We conclude that, as has already been reported for people with anorexia nervosa, considering one's own body to be fatter than it really is leads to congruent weight-related behavior.