A New Technique for Estimating Body Size and Dissatisfaction

A disturbed body image is common among persons with anorexia nervosa and bulimia nervosa, and is clinically and diagnostically important. A group at Oxford University has proposed a method for assessing body size estimation and body size dissatisfaction using mirror testing (Int J Eat Dis 2002; 32:458).

According to Drs. Roz Shafran and Christopher Fairburn, a major problem with existing research on body image is that patients estimate their size and report their dissatisfaction by using “life-size” images, usually in a mirror. This leads to a problem because the viewer assumes that the life-size image she sees is accurate, when it is not. In fact, the actual size of our reflection in a mirror is half our body size in real life. For example, the length of a mirror reflection of a person 160 cm in height and standing 1 meter away from a full-length mirror is actually 80 cm, not 160 cm.

Thus, to make clinical research on body size estimation and dissatisfaction clinically relevant, the authors developed a method for assessing perception of body size that resembled the real-life situation of looking at oneself in a mirror. They also sought to use the new method to provide preliminary data on body size estimation and body size dissatisfaction in participants with eating disorders and a group of controls. Fourteen women had eating disorders that were clinically severe: 4 had anorexia nervosa, 3 had bulimia nervosa, and 7 had eating disorders not otherwise specified (EDNOS). Twenty-four women without eating disorders were included as controls.

Method

All women completed the Eating Disorder Examination Self-Report version (EDE-Q) on the day of, or a day before, their appointment. The day of their appointment, the women undressed down to their underwear in a darkened room with standardized lighting and stood opposite a full-length mirror at one end of the room. They stood as close to the mirror as they normally would when judging their size at home. The female researcher then stood beside the participant, facing the mirror, and photographed the participant’s reflection in the mirror with a digital camera positioned next to the participant’s eyes.

While checking with the participant, the researcher then marked the position on the mirror of the top of the participant’s head and the position of the participant’s toes.

The participant then read a neutral travel or news magazine while the digital image of the participant’s mirror reflection was downloaded to a computer. All other data except the participant and the mirror were removed from the image (because of the position, the researcher and camera were invariably included in the initial image). The final edited photograph was then projected onto a full-length screen next to the mirror so that the head and feet of the projected image were at the same height from the floor as the participant’s reflection in the mirror. The participant then was asked to stand at the same distance from the mirror as during the test, and was told that the photograph of her reflection in the mirror would be projected either wider than her true reflection, the same width as her true reflection, or narrower than her true reflection. The participant was asked to tell the researcher to adjust the projected image so that it matched “exactly what you see in the mirror.” For the body size estimation task, the participant was encouraged to look across at her reflection in the adjacent mirror and to adjust the projected image. Each task was completed twice, once starting with the image 50% wider than the participant’s actual reflection and once with the image 50% narrower than the actual reflection.

At the end of the experiment, the woman was weighed and her height was measured. She was also told how accurate she was at estimating her body size and was informed about the discrepancy between her actual size and desired size.

Results

As expected, participants with eating disorders scored significantly higher on subscales of the EDE-Q and the global EDE-Q, and had significantly lower body mass indexes than the women without eating disorders. The group with eating disorders also overestimated their body size by a mean of 17% compared with controls. On average, those with eating disorders reported that they wished to be 23% smaller than their actual size and there was a trend for those with eating disorders to be more dissatisfied with their body size than were controls.

The aim of this study was to develop a method for assessing the perception of body size that resembled the real-life situation of seeing oneself in a mirror, rather than their memory of body size. Because mirrors are the most obvious and common ways in which people judge their body size, using the mirror method resembles the real-life situation of viewing oneself in a mirror. Some patients with eating disorders persistently look in the mirror, which can play an important role in maintaining an eating disorder.

The authors do point out that their study was small and was designed to develop a new method of assessing perception of body size and body size dissatisfaction, not to test hypotheses about patients with eating disorders and non-eating disordered controls. Thus, the results shouldn’t be used to draw conclusions about different types of eating of eating disorders.