Onset of adolescent eating disorders: population based cohort study over 3 yearsBMJ 1999; 318 doi: https://doi.org/10.1136/bmj.318.7186.765 (Published 20 March 1999) Cite this as: BMJ 1999;318:765
All rapid responses
EDITOR - In a recent article, Patton et al. reported a positive
association between dieting and the development of eating disorders in
adolescents (1). A causal effect of dieting on the development of these
serious psychiatric conditions was implied in the conclusion. However, we
believe that the data presented did not support the suggested causal
Unlike in a randomized clinical trial, the subjects of a cohort study
select themselves to the exposure of interest, in this case to dieting. It
is possible that the subjects at risk of developing eating disorders were
more likely to expose themselves to dieting. In order to avoid this bias,
the exposed and unexposed subjects of a cohort study should be similar for
other important determinants of outcome (3). There is no evidence that
this was true in this study. In fact, after adjustment for psychiatric
disorders at baseline, the hazard ratio of severe dieting decreased three
folds, suggesting that the exposed and unexposed groups might have
differed for other unadjusted factors.
In a cohort study, the subjects must be free of the disease at
inclusion (3). Although the 37 incident cases might not have displayed, at
baseline, all the signs necessary for the diagnosis of eating disorder, it
is possible that some of these who were on diet at the beginning of the
study, were actually in the early stages of an eating disorder. Similarly,
a cohort study could suggest that weight loss is a risk factor for AIDS,
if it did not screen for HIV infection at baseline. Weight loss is an
early, non-specific symptom of HIV infection, as dieting might be an
early, non-specific sign of latter development of eating disorders, and
not a cause.
Although some of these points were raised in the discussion, the
conclusion and key messages emphasized that adolescents who diet are at
increased risk for the development of an eating disorder. We agree that
inappropriate dietary behaviors should be discouraged, but given the
global epidemic of obesity, the importance of promoting of a healthy life
style, including weight control by a reasonable diet and exercise, should
be emphasized for all adolescents.
Andrew M Tershakovec
Associate Professor of Pediatrics
Department of Gastroenterology and Nutrition
The Children's Hospital of Philadelphia
34th Street and Civic Center Boulevard
Philadelphia, PA 19104-4399
Mary B. Leonard
Assistant Professor of Pediatrics and Epidemiology
Center for Clinical Epidemiology and Biostatistics
University of Pennsylvania
726 Blockley Hall
423 Guardian Drive
Philadelphia, PA 19104-6021
1 Patton GC, Selzer R, Coffey C, Carlin JB, Wolfe R. Onset of
adolescent eating disorders: population based cohort study over 3 years.
BMJ 1999; 318:765-8. (20 March.)
2 Evans AS. Causation and disease: the Henle-Koch postulates
revisited. Yale Journal of Biology & Medicine1976; 49:175-95.
3 Levine M, Walter S, Lee H, Haines T, Holbrook A, Moyer V. Users'
guides to the medical literature. IV. How to use an article about harm.
Evidence-Based Medicine Working Group. JAMA 1994; 271:1615-9.
Competing interests: No competing interests