Weight, reference points, and the onset of eating disorders.

We investigate whether the development of eating disorders, in the form of purging, is influenced by peers' body size through interpersonal comparisons. Using detailed information on recent cohorts of U.S. teenagers, we document a sizeable and significant negative effect of high school peers' body mass index (BMI) on purging behavior during the adolescence for females, but not for males. Interpersonal comparisons operate through the formation of a distorted self-perception: teenage girls with relatively thin female peers perceive themselves as heavier than they actually are. The girls who are more susceptible to peer influences are those having peers who are thinner, more popular, more (verbally) able, and with more educated parents.