Changes in Bioimpedance analysis after stable refeeding of undernourished anorexic patients

OBJECTIVE: To evaluate bioimpedance analysis (BIA) parameters in patients with anorexia nervosa when undernourished and then after stable refeeding. DESIGN: Follow-up study. SUBJECTS: Thirteen patients with anorexia nervosa who were studied when undernourished (body weight (Wt): 36.9 ± 5.6 kg, body mass index (BMI): 14.8 ± 1.8 kg/m²) and after stable refeeding (Wt: 52.9 ± 7.1 kg, BMI: 21.2 ± 2.3 kg/m²) compared to 25 well-nourished control women (Wt: 53.7 ± 4.9 kg, BMI: 21.1 ± 1.3 kg/m²). MEASUREMENTS: Impedance and phase angle were determined for the whole body (13 patients) and separately for arms and legs (10 patients). RESULTS: Bioimpedance index (height²/impedance) and phase angle were lower in the undernourished group. Whole body impedance declined (median, min-max) by 45, 1-151 Ohm after refeeding; the variations of bioimpedance index (BI-Index) were weakly correlated (P <0.10) with BMI changes. Limb phase angles increased with refeeding, but only changes in whole-body phase angle were correlated (P <0.025) with the corresponding variations of Wt or BMI. CONCLUSION: Whole-body phase angle increased after weight recovery of anorexic patients, suggesting the occurence of modifications in the extracellular-to-intracellular water ratio. These changes were proportional to the increase in BMI and Wt.