Bioimpedance and bioimpedance vector analysis in patients with anorexia nervosa

The utility of bioelectrical impedance analysis (BIA) in patients with anorexia nervosa (AN) is imperfectly defined. Furthermore, any advantage accrued by BIA with vector analysis (BIVA) is unknown.

We conducted a retrospective analysis of 57 women with AN admitted to our service who underwent BIA and BIVA. Twenty-seven women were observed during short-term (3 weeks) and 13 women during longer-term (3 months) weight gain.

Bioelectrical impedance analysis produced implausible results in 47% of the patients. BIVA demonstrated low body cell mass and highly variable extracellular water (ECW) volume, ranging from volume contraction to volume expansion on admission and during treatment. BIVA suggested that short-term weight gain predominantly consisted of ECW volume, whereas longer-term weight gain resulted in increased hydrated body cell mass.

Conventional BIA has little utility in these patients. However, BIVA could be a suitable alternative in the medical management reflecting ECW volume changes and later genuine tissue mass increases.