One study that compared anorexia or bulimia patients with groups of healthy control participants found that anorexia or bulimia patients overestimated their waist width by 42 percent. Similar results have been found for several regions of the body, but the waist, hips, shoulders and face were most commonly measured.

Healthy participants overestimated their bodies too. For example, one study found healthy adults overestimated the width of their waists by nearly 24 percent, the chest by 23 percent, and the hips by 13 percent.

In one study, participants' hands were covered with a board and then asked to use a long baton to indicate the perceived location of the knuckle and tip of each finger. Perceptual maps of hand size and shape were constructed based on their judgements and then compared with the actual hand structu...