Body image can alter how anorexic women move around, without them realizing it. According to a study published in PLoS One, anorexic patients not only think of themselves of fat, but also go as far as to unconsciously adjust the way they walk to avoid objects they aren't going to hit.

"It appears that for anorexia nervosa patients, experiencing their body as fat goes beyond thinking and perceiving themselves in such a way, it is even reflected in how they move around in the world," wrote the authors.

Nearly two million people in the U.S. suffer from anorexia, and the majority are teenage or college-aged women. While a keen awareness of self-image is common in this age demographic, people with anorexia push the limits of this tendency and obsess over the perception of their own body image. This manifests into extreme, sometimes fatal, dieting.

The mental disorder is typified by patients sincerely believing their body is fatter than it actually is.

Dutch researchers from Utrecht University wondered if these distorted views change how anorexics interact with the world.

Thirty-nine female undergraduates were recruited for this study; 13 had anorexia, 6 subjects had "Eating Disorder Not Otherwise Specified" (EDNOS) - which shares many symptoms with anorexia, but doesn't fit the full disease criteria - and 20 were healthy controls. All subjects were over the age of 18.

Two tables were placed on opposite sides of a room, and the subjects were asked to walk from one to the other, while passing through a 'doorway' in the middle of the room. They repeated this task multiple times, but what they didn't know was the width of the doorway was narrowed slightly between each trial.

To distract them from this fact, the subjects were told that they were participating in a memory experiment. Before crossing the room, each woman was asked to rub her finger across a rough strip of sandpaper lying on the first table.

The destination table had two different pieces of sandpaper, and the subjects were asked to mark down which piece resembled the one from before.

By occupying their minds with this fake memory challenge, the women failed to notice the doorway becoming narrower. A set of video cameras, hung from above, were used to track how their gait and shoulder angles as they walked.

When the opening was 40 percent wider than their shoulders, anorexic women began rotating their bodies to squeeze through the passage. Healthy women didn't begin to sidestep through the door until it was 25 percent wider than their shoulders.

Subjects were asked to estimate the width of their shoulders. On average, female undergrads with eating disorders believed their shoulders were 10 inches wider than they actually were, while estimates from healthy women were closer to the truth - only four inches over.

This is one of the first studies to connect body representation to physical actions in the context of eating disorders, according to the authors, and it could impact how psychologists treat the disease.

"Current therapeutic interventions should not only focus on changing how patients think about their body and how they look at it, but also target the body in action," said first author Anouk Keizer, an experimental psychologist and Ph.D. student at Utrecht University. "In other words, treatment should aim to improve the experience of body size as a whole."

Source: Keizer A, Smeets MAM, Dijkerman HC. Too Fat to Fit through the Door: First Evidence for Disturbed Body-Scaled Action in Anorexia Nervosaduring Locomotion. PLoS One. 2013.