[Evaluation of body composition in anorexia nervosa]

Bioimpedance analysis (BI) of body composition has been carried out in 116 women: 22 patients with anorexia nervosa (AN) and IMC between 16 and 18.5 kg/m2 (MPE-I: weight 45.3+/-3.1 kg; BMI 17.0+/-0.7 kg/m2); 39 AN patients with BMI< 16 kg/m2 (MPE-II: weight 37.2+/-3.8 kg; BMI 14.5+/-1.0 kg/ m2; 55 healthy women (control= CTR: weight 60.5+/-9.0 kg; BMI 22.8+/-3.1 kg/m2). BI was determined for the whole body and for body segments (arms, legs and trunk): phase angle (AF) of 50 kHz and impedance (Z) of 100, 50 and 5 kHz. Body water was estimated from Z to 50 kHz according to Kushner et al. (AJCN 1993). AF and Z100/Z5 (multifrequency BI) were considered as related to the ratio between extracellular water and intracellular water. Total body water was significantly different between the three groups: 26.5+/-2.9 L in the MPE-II group, 23.6+/-2.9 L in the MPE-I group; 30.3+/-3.7 L in the CTR women. In comparison with the CTR group whole-body AF and leg-AF was lower (p<0.01) in the MPE-II patients while both the MPE groups differed from the CTR group with respect to arm-AF. Multifrequency BI showed differences (p<0.01) between all the groups for the whole-body and segmental measures. Significant correlations for AF and Z100/Z5 vs BMI and % BF were apparent only in the MPE-II group. In conclusion, in the AN the marked modifications of BI parameters indicated a relative increase of extracellular water and were related to BMI and % BF in the very undernourished patients.