Bioelectrical impedance phase angle in constitutionally lean females, ballet dancers and patients with anorexia nervosa.

BACKGROUND/OBJECTIVE: Several articles have described body composition in anorexia nervosa, whereas little is known about this issue in underweight ballet dancers and constitutionally lean females. The main aim of this study was to assess whether phase angle (a bioimpedance variable related to body cell mass) differs according to the type of underweight in female adolescents and young women.

SUBJECTS/METHODS: Skinfold thicknesses and bioimpedance analysis (whole body and limbs) were evaluated in three groups of underweight patients (30 patients with anorexia nervosa, 10 constitutionally lean individuals and 15 classical dancers) and 30 normal weight controls.

RESULTS

There were no differences between the three groups of underweight patients with respect to anthropometric and bioelectrical impedance analysis (BIA) variables with the exception of phase angle. The latter was significantly higher in dancers, lower in anorectic patients and not different in constitutionally lean patients, as compared with controls.

CONCLUSIONS

Phase angle (assessed by single-frequency BIA) appears to discriminate between different forms of underweight, being an effective marker of qualitative changes in body composition.