Differentiating anorexia nervosa and atypical anorexia nervosa with absolute weight cut‐offs results in a skewed distribution for premorbid weight among youth

In this special issue, international researchers investigate how atypical anorexia nervosa (atypical AN) differs from anorexia nervosa (AN) and other eating disorders with respect to demographics, psychological and physiological morbidity, as well as treatment course and outcome. Manuscripts in this special issue report that atypical AN is associated with substantial medical and psychological morbidity, and the majority of studies find few differences between atypical AN and AN. While much remains to be learned about the long‐term course and treatment response of individuals with atypical AN to psychological and pharmacological interventions, the evidence supports conceptualization of atypical AN as part of a spectrum‐based restrictive eating disorder. These findings together with the potentially stigmatizing use of the term “atypical” suggest it may be time to revise the existing definition of atypical AN.

Time to revisit the definition of atypical anorexia nervosa

Golden,

Walsh

2024

Premorbid body weight predicts weight loss in both anorexia nervosa and atypical anorexia nervosa: Further support for a single underlying disorder

Hebebrand,

Seitz,

Föcker

et al. 2024

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ObjectiveFor adolescents, DSM‐5 differentiates anorexia nervosa (AN) and atypical AN with the 5th BMI‐centile‐for‐age. We hypothesized that the diagnostic weight cut‐off yields (i) lower weight loss in atypical AN and (ii) discrepant premorbid BMI distributions between the two disorders. Prior studies demonstrate that premorbid BMI predicts admission BMI and weight loss in patients with AN. We explore these relationships in atypical AN.MethodBased on admission BMI‐centile < or ≥5th, participants included 411 female adolescent inpatients with AN and 49 with atypical AN from our registry study. Regression analysis and t‐tests statistically addressed our hypotheses and exploratory correlation analyses compared interrelationships between weight loss, admission BMI, and premorbid BMI in both disorders.ResultsWeight loss in atypical AN was 5.6 kg lower than in AN upon adjustment for admission age, admission height, premorbid weight and duration of illness. Premorbid BMI‐standard deviation scores differed by almost one between both disorders. Premorbid BMI and weight loss were strongly correlated in both AN and atypical AN.DiscussionWhereas the weight cut‐off induces discrepancies in premorbid weight and adjusted weight loss, AN and atypical AN overall share strong weight‐specific interrelationships that merit etiological consideration. Epidemiological and genetic associations between AN and low body weight may reflect a skewed premorbid BMI distribution. In combination with prior findings for similar psychological and medical characteristics in AN and atypical AN, our findings support a homogenous illness conceptualization. We propose that diagnostic subcategorization based on premorbid BMI, rather than admission BMI, may improve clinical validity.Public significanceBecause body weights of patients with AN must drop below the 5th BMI‐centile per DSM‐5, they will inherently require greater weight loss than their counterparts with atypical AN of the same sex, age, height and premorbid weight. Indeed, patients with atypical AN had a 5.6 kg lower weight loss after controlling for these variables. In comparison to the reference population, we found a lower and higher mean premorbid weight in patients with AN and atypical AN, respectively. Considering previous psychological and medical comparisons showing little differences between AN and atypical AN, we view a single disorder as the most parsimonious explanation. Etiological models need to particularly account for the strong relationship between weight loss and premorbid body weight.

What Amount of Weight Loss Can Entail Anorexia Nervosa or Atypical Anorexia Nervosa After Bariatric Surgery?

Hebebrand,

Antel,

Conceição

et al. 2024

ObjectivePost‐operative development of restrictive eating disorders can occur in patients after bariatric surgery. In children and adolescents with anorexia nervosa (AN) or atypical AN, premorbid body mass index (BMI) has recently been shown to predict total weight loss. We hypothesized that pre‐operative BMI similarly predicts weight loss and the development of a restrictive eating disorder in adult bariatric patients.MethodA PubMed search identified case studies/series of 29 adult females who developed AN or atypical AN/eating disorder not otherwise specified following bariatric surgery. Non‐parametric Spearman's correlation (r s ) between pre‐operative BMI and total weight loss was calculated; a scatterplot was used to illustrate the relationship between pre‐operative/premorbid BMI and weight loss in kg for 29 bariatric patients and 460 children and adolescents with AN or atypical AN as published previously.ResultsThe correlation between pre‐operative BMI and weight loss among bariatric patients was r s = 0.65 (p = 0.0001). Scatterplot data of this relationship fit the previously identified pattern in children and adolescents with AN or atypical AN.DiscussionThe prediction of weight loss by pre‐operative/premorbid BMI appears applicable across the weight spectrum, from underweight to severe obesity, thus strengthening our hypothesis of underlying regulatory mechanisms for the development of AN and atypical AN. Such data may guide the determination of critical weight loss thresholds that trigger eating disorder development in predisposed individuals.