Body weight distortions in an auditory-driven body illusion in subclinical and clinical eating disorders

Previous studies suggest a stronger influence of visual signals on body image in individuals with eating disorders (EDs) than healthy controls; however, the influence of other exteroceptive sensory signals remains unclear. Here we used an illusion relying on auditory (exteroceptive) signals to manipulate body size/weight perceptions and investigated whether the mechanisms integrating sensory signals into body image are altered in subclinical and clinical EDs. Participants; footstep sounds were altered to seem produced by lighter or heavier bodies. Across two experiments, we tested healthy women assigned to three groups based on self-reported Symptomatology of EDs (SED), and women with Anorexia Nervosa (AN), and used self-report, body-visualization, and behavioural (gait) measures. As with visual bodily illusions, we predicted stronger influence of auditory signals, leading to an enhanced body-weight illusion, in people with High-SED and AN. Unexpectedly, High-SED and AN participants displayed a gait typical of heavier bodies and a widest/heaviest visualized body in the light's; footsteps condition. In contrast, Low-SED participants showed these patterns in the 'heavy'; footsteps condition. Self-reports did not show group differences. The results of this pilot study suggest disturbances in the sensory integration mechanisms, rather than purely visually-driven body distortions, in subclinical/clinical EDs, opening opportunities for the development of novel diagnostic/therapeutic tools. This project has also received funding from the ERC under the European Union's Horizon 2020 research and innovation programme (grant agreement No 101002711), as well as from the Ministerio de Economía, Industria y Competitividad of Spain RYC-2014-15421 and PSI2016-79004-R (AEI/FEDER, UE) and by the Spanish Agencia Estatal de Investigación (PID2019-105579RB-I00/AEI/10.13039/501100011033) grants awarded to A.T. L.C. was partially supported by an Erasmus+ training programme and J.L. by the doctoral training grant BES-2017-080471.