Assessment of Sex Differences in Body Composition Among Adolescents With Anorexia Nervosa.

PURPOSE: To compare deficits in fat mass (FM) and lean body mass (LM) among male and female adolescents with anorexia nervosa (AN) and to identify other covariates associated with body composition.

METHODS: We retrospectively reviewed electronic medical records of all subjects aged 9-20 years with a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition diagnosis of AN and dual-energy x-ray absorptiometry scans after initial evaluation at Stanford between March 1997 and February 2011. From the dual-energy x-ray absorptiometry scans, LM and FM results were converted to age-, height-, sex-, and race-specific Z-scores for age using the National Health and Nutrition Examination Survey reference data.

RESULTS: A total of 16 boys and 119 girls with AN met eligibility criteria. The FM Z-score in girls with AN (-3.24 ± 1.50) was significantly lower than that in boys with AN (-2.41 ± .96) in unadjusted models (p = .007). LM was reduced in both girls and boys with AN, but there was no significant sex difference in LM Z-scores. In multivariate models, lower percentage median body mass index was significantly associated with lower FM Z-scores (β = .08, p < .0001) and lower LM Z-score (β = .03, p = .0002), whereas lower whole body bone mineral content Z-score was significantly associated with lower LM Z-score (β = .21, p = .0006).

CONCLUSIONS: FM deficits in girls were significantly greater than those in boys with AN in unadjusted models; however, the degree of malnutrition appeared to be the primary factor accounting for this difference. There were no significant sex differences in FM or LM in adjusted models.