Anorexia Nervosa as a Disorder of Embodiment: the Role of Interoception

Anorexia nervosa (AN) has the highest mortality rate of any mental health condition[1]. Though
primarily characterised as a body image disorder, recent developments suggest AN may be better
characterised as an embodiment disorder[2].
In predictive coding accounts, a coherent sense of self results from the multi-sensory integration
(MI) of interoceptive (internal bodily signals e.g. heartbeats) and exteroceptive (external bodily
signals e.g. vision) streams with top-down predictions about the body[3]. When sensory input and
predictions are incongruent, stored body representations can update to mitigate future prediction
error. In AN, interoceptive streams are postulated to be noisy, meaning they are assigned low
precision during MI[4]. According to the optical-coenesthetic disproportion hypothesis (OCDH;[5]),
the resulting dominance of exteroceptive signals (primarily vision) during MI due to little
interoceptive reinforcement, causes the individual to become disembodied, viewing themselves as
an object within an environment. This disembodied perspective increases self-objectification and body dissatisfaction, culminating in the generation of excessively specific predictions about the
body's shape[6]. Moreover, imprecise, noisy interoceptive signals are not strong enough to
contradict highly precise predictions. Resultantly, any prediction errors generated by perceived
changes in bodily dimensions with weight loss are insufficient to update stored body
representations. Hence, individuals become locked to out-dated stored body representations,
resulting in body distortions.
Supporting this hypothesis, interoceptive awareness, including of heartbeats[7] and satiety[8], is
altered in AN. Critically, ownership in the rubber hand illusion is elevated in AN relative to healthy
controls (HC) and is predicted by eating disorder psychopathology, interoceptive deficits, and selfobjectification[
9]. This suggests visual signals are prioritised over interoceptive signals during MI of
the self in AN. Furthermore, body size during egocentric body-related judgements (e.g. aperturepassing
tasks) is consistently overestimated in AN and this correlates with pre-illness body
weight[10]. Thus, out-dated body representations appear to dominate in AN.