Among 12 534 adolescents participating in GUTS followed up for 7 years, we observed that 10% of the females and 3% of the males started engaging in bulimic behaviors frequently. Contrary to expectations, we observed that the incidence of purging was higher than the incidence of binge eating among the females. For a diagnosis of bulimia nervosa, an individual must engage in both binge eating and purge behaviors frequently, a combination that few of the frequent binge eaters or purgers in the cohort exhibited. For a diagnosis of binge eating disorder, one must engage in frequent binge eating episodes but exhibit no compensatory behaviors. Our findings suggest that by examining only those 2 combinations of symptoms, a large group of females who purge frequently but do not binge eat frequently are overlooked.24,25
Our finding that a maternal history of an eating disorder is a risk factor for starting to purge among preadolescent and young adolescent females is consistent with findings by Bulik et al,26
who found strong evidence of heritability of anorexia nervosa in a large population-based sample of Swedish twins, and by Reichborn-Kjennerud et al,27
who found strong evidence for a genetic component to binge eating in a sample of 8045 same-sex and opposite-sex Norwegian twins. Neither of these studies found much support for the shared environment being associated with the outcome. However, in the present study, we were unable to determine whether the association with maternal history of an eating disorder was due to genetics or to shared environment. Few studies that have assessed whether subjects with early vs later onset of a disorder vary in terms of the influence of genetics on the risk of becoming eating disordered.28–30
More research is needed to better understand these associations.
Although teasing or negative comments about weight have been proposed as risk factors for becoming eating disordered, the evidence is mixed. Haines et al10
found that the females in Project EAT (Eating Among Teens) who were teased were more likely to become frequent dieters 5 years later, but they did not observe an association between teasing and the development of bulimic behavior. In contrast, among the males, those who had been teased were more likely than their peers to start binge eating, which is consistent with our finding that among the males in GUTS, teasing or negative comments about weight by their fathers was predictive of starting to binge eat. Among the females, teasing by mothers, fathers, and other females was unrelated to the risk of starting to binge or purge weekly, but teasing about weight by males was associated with an increase in the risk of starting to purge weekly. Inasmuch as only teasing by males was predictive among the females in our sample, it is possible that the lack of association by Haines et al10
may reflect grouping of all types of teasing together or the result of not considering purging an outcome.
The role of the media in the development of eating disorders continues to be controversial. Many cross-sectional studies have observed an association between frequency of exposure to the mass media, particularly the print media, and body dissatisfaction and disordered eating,20,31,32
but the results of these studies have been questioned because individuals who are very dissatisfied with their weight or shape might seek out magazines and other forms of media as a result of body dissatisfaction rather than the opposite temporal order of association that is assumed. Stronger evidence comes from a few prospective investigations that have observed an association between exposure to the media and the development of disordered eating among young females.1–3,33,34
In the present study, we observed that trying to look like same-sex persons in the media was a stronger risk factor for females than for males, which suggests that programs to prevent the development of bulimic behaviors should incorporate media literacy in their lesson plans.
Dieting and high level of concern about weight were strong risk factors for all outcomes among females. These findings highlight the need for parents and health care providers (all medical professionals who might deliver care to this age group) to not dismiss dieting and negative comments about body weight as harmless rites of passage among young females; rather, they should be thought of as potential warning signs to be investigated further. Although dieting was a risk factor for all of the outcomes, there were notable differences in predictors of starting to binge eat, starting to purge, and starting to binge eat and purge. For example, among the females, peer influences had a much stronger association with starting to binge eat and purge weekly than with starting to engage in only 1 bulimic behavior. Moreover, risk factors differed by age and sex. Purging frequently, regardless of whether someone binge eats, is a cause for concern and warrants treatment.
A limitation of our study is that it does not represent a random sample of all US adolescents and young adults. The participants were children of nurses and the sample was more than 90% white; thus, it is unlikely that there were children of low socioeconomic status in the sample. Therefore, it is unclear whether the results of the study are generalizable to nonwhite ethnic groups or to economically disadvantaged populations. However, there are many strengths to the current study that offset this limitation. The study is the largest study of disordered eating with repeated assessments of a wide range of exposures and a long follow-up. In addition, the study was sufficiently large to assess risk factors separately by age group (among the females) and sex, which proved important because risk factors varied by age group among the females.
Our results suggest that prevention of disordered eating and eating disorders may need to be age- and sex-specific. Efforts aimed at females should contain media literacy and other approaches to make young persons less susceptible to the media images they see. In addition, programs for females should focus more on becoming more resilient to teasing from males, whereas programs for males should focus on approaches to becoming more resilient to negative comments about weight by fathers. Although males are less likely than females to develop disordered eating, parents and clinicians should be aware that negative comments about weight can have serious consequences such as making young males more likely to start binge eating frequently. It is, therefore, of utmost importance that parents, teachers, and clinicians promote maintaining a healthy weight without overemphasizing the importance of weight or stigmatizing overweight youth.