Predictors of Complications in Anorexia Nervosa and Atypical Anorexia Nervosa: Degree of Underweight or Extent and Recency of Weight Loss?

Purpose: Adolescents with atypical anorexia nervosa (AAN) can experience severe physical complications despite not being underweight, posing questions about the contribution of weight loss to complications experienced in restrictive eating disorders (EDs). This study compared total weight loss and recent weight loss with admission weight as predictors of physical and psychological complications.

Methods: Retrospective (2005-2010) and prospective (2011-2013) studies were undertaken of 12- to 19-year-old hospitalized adolescents with anorexia nervosa (AN) or AAN, defined as meeting criteria for AN except underweight (≥85% median body mass index). Predictors were total weight loss (from lifetime maximum), recent weight loss (past 3 months), and admission weight. Outcomes were hypophosphatemia, clinical, anthropometric, and psychometric markers during admission.

Results: In 171 participants (AN, 118 [69%]; AAN, 53 [31%]), there was little evidence of an association between weight measures and hypophosphatemia. Greater total weight loss (regression coefficient [Coeff]: -1.70, 95% confidence interval [CI]: -2.77, -.63, p = .002) and greater recent weight loss (Coeff: -3.37, 95% CI: -5.77, -.97, p = .006), but not admission weight, were associated with a lower pulse rate nadir. Greater total weight loss (odds ratio [OR]: 1.70, 95% CI: 1.19, 2.24, p = .003) and greater recent weight loss (OR: 2.12, 95% CI: 1.11, 4.02, p = .02) were also associated with a higher incidence of bradycardia.

Conclusions: In adolescents with restrictive EDs, total weight loss and recent weight loss were better predictors than admission weight of many physical complications. This suggests that future diagnostic criteria for AN place greater emphasis on weight loss.