Evaluation of Methods to Assess Reduced Body Fat in Patients with Anorexia Nervosa

Objective: To evaluate skinfold anthropometry and dual-energy x-ray absorptiometry (DXA) to estimate percentage of body fat (%BF) in adolescent patients with anorexia nervosa (AN). Methods: We examined 80 female AN patients (age 15.6 +/- 1.4 years) and 31 healthy, normal weight sex- and age-matched controls with DXA and skinfold anthropometry to estimate %BF. Reference values for %BF of the same participants were obtained from a 4-compartment (4C) model, which was based on measurements of total body protein (with in vivo neutron activation), total body water (with deuterium dilution), and mineral content (with DXA). We compared the different methods to assess %BF with Bland-Altman analysis of agreement. Results: In the AN group, average %BF was well predicted with DXA and skinfold measurements in combination with the Deurenberg equation based on 2 skinfolds (DXA 13.9 +/- 6.2 %BF; skinfold 14.5 +/- 4.3 vs 14.1 +/- 6.8 %BF by the 4C model). In the control group, average %BF was closely predicted by skinfold measurements in combination with the Slaughter formula (26.1 +/- 4.5 vs 25.2 +/- 5.2 %BF by the 4C model) but was overestimated with DXA (31.3 +/- 5.8 %BF). When compared with the 4C model, all methods under investigation showed considerable limits of agreement when predicting %BF in any given individual. Conclusions: In our group of patients with AN, the Deurenberg skinfold model and DXA were similar in performance; however, DXA overestimated %BF in healthy subjects.