Through a door sideways: Body size distortion in anorexia
When I was a grad student in Baltimore, I lived in a 400 square foot studio apartment. Two of the doors were normal sized (the front door and the one to the bathroom), but one that opened off from the bedroom into the back bathroom area was narrow. As in, I had to be careful when I walked through so I didn’t dislocate a shoulder. Cognitively, I knew that it was a small doorway, but it always made me feel huge to walk through it and realize that I was literally filling the entire doorway.
In the middle of the night especially, my strategy was to scoot through the door sideways to keep from smacking a shoulder, elbow, knee, or toe. Even during the day, I angled my body.
In order to fit ourselves through openings like doors, we need to have a basic idea of the rough size of our bodies. Our brains don’t necessarily think in inches or pant sizes. But most of us have a semi-accurate idea of our general size and shape and the types of doorways through which we can fit. People with anorexia nervosa aren’t most people. In a virtual reality setting, people with AN angled their bodies to walk through doorways that were much larger than their actual bodies. These results show that the feelings of “fat” frequently seen in AN aren’t just emotional–they’re also physical (Keizer et al., 2013).
Body image vs. body schema
Most of the research literature looking at body-related issues in EDs looks at body image. To neuroscientists, body image is simply the picture we have in our heads of what we look like. All of us probably have some small distortions in our body image, whether its temporary (a zit that seems to take up our whole entire face) or more permanent (seeing really crooked teeth when they’re not that bad). For most people, these perceptions are broadly accurate. We may not feel we measure up to cultural standards set in magazines, but generally, body image is pretty accurate.
Body schema sounds similar to body image, but there are some important differences, too. Whereas body image is primarily related to how we see and think about ourselves, body schema is related to how we actually move through the physical world. Body image asks if we think of ourselves as tall; body schema asks whether we duck when walking under that low-hanging living room chandelier. The two concepts are related, but still separate (you can feel too short but still duck appropriately, thus having a problem with body image rather than body schema).
Although I’ve blogged before about body size perception in AN, there has been much less work done in the area of body schema. What researchers didn’t really know was how much the body image distortion in AN extended into the physical realm. A common component of ED treatment is a body tracing, where you draw out what you think the outline of your body is and then the therapist traces your actual body. Shock of shocks, your perceived outline of your body is larger than the therapist’s tracing. The problem is that this still gets at body image rather than body schema as the setup is really artificial.
(I was terrified that my drawing would be bigger than my actual size and I would have to cope with the fact that I was actually even fatter than I thought, so I’m guessing my outline wasn’t all that accurate anyway. I also got into a yelling match with the therapist who tried to tell me that the large head I drew represented the fact that I lived exclusively in my head. I told her I sucked at art and I was just slapping an elliptical item onto the paper so I could put the damn marker down. But that’s another story).
To measure body schema in the real world, researchers at Utrecht University in the Netherlands, led by Anouk Keizer, filmed study participants walking through wall openings of a variety of widths. This way, they could get more precise measurements of how people moved their bodies through space and time. To keep them from overthinking the subject, study participants were given a diversion task to keep their conscious minds off the wall opening so that their natural body schema could be observed at work.
So about that doorway. Like my nighttime escapades in Baltimore, people generally angle their bodies to get through narrow doorways. Previous studies have shown that they do this when a doorway is no more than slightly wider than they are. Researchers measure this in the ratio of doorway width to shoulder width. This ratio was shown to be constant regardless of body size or height.
Using 19 ED patients with AN (n=13) or EDNOS, AN-type (n=6), along with 20 healthy controls, the researchers asked them to walk through doorways of various widths. Using special markers the participants wore on their shoulders, the cameras recorded if the participant angled their body to get through the opening.
Whereas healthy controls began to rotate their bodies to fit through a doorway that was 25% wider than their shoulders, the AN patients began rotating when the doorway was 40% larger. The rotating ratio didn’t depend on the person’s BMI, how long they had been ill, or how fast they were walking. When the patients were asked to select the smallest opening through which they could fit without rotating (an estimation of their body size perception), the AN patients consistently picked a wider doorway than healthy controls.
The initial explanation for this was that the brain hadn’t updated the much smaller body size as a result of the AN. It was stuck on the original pre-illness body size. The problem is that some of these patients had been ill for years, which would give the neural circuits plenty of time to update the new body size information. Hypothesis #2 was that maybe the circuits can’t update and the patient is mentally stuck at whatever their pre-illness body size was. Except the EDNOS patients included in the study were weight-restored or partially weight-restored AN patients, and they rotated just as much as the more significantly underweight AN patients. One option is that something happens before or concurrent with illness onset that monkeys with how the brain perceives body size. Researchers aren’t really sure what causes this.
The authors conclude that:
Thus, AN patients do not only think that they are fat, and perceive themselves as fat, even their motor behaviour is consistent with such beliefs and perceptions, as patients were found to walk through a door-like opening as if they were fatter than they actually were. Our study is the first that directly targets action-related body representation disturbances in AN…Although AN patients are chronically aware of their body (size), it is unlikely that here their decision to either rotate while crossing an aperture, or walk straight through, was consciously influenced by negative affective/emotional top-down input related to their body size…
However, the current study does imply that body size related distortions in AN are more pervasive than previously assumed, and that they affect not only perception, but action as well, which has important implications for treatment. Usually the aim of interventions targeting the disturbed experience of the body in AN is changing cognitions and perception of body size. Several studies have shown that such approaches are not always efficient, as after otherwise successful treatment, body-size issues remain. This may be because current interventions mainly attempt to change aspects of body image, and not of body schema. It could therefore be relevant to design a treatment strategy in which action related responses are targeted as well…It thus appears that for AN 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. This indicates that the disturbed experience of body size in AN is more pervasive than previously assumed.