Potential bioelectrical impedance analysis (BIA) parameters in prediction muscle strength in women with anorexia nervosa.

Objectives: The role of physical activity in anorexia nervosa (AN) treatment has been investigated. Muscle strength (MS) reflects physical condition and can predict AN patients' response to this novel treatment approach. This study was intended to find bioelectrical impedance analysis (BIA) parameters that predict AN patients' MS.

Methods: The study included 42 AN patients and 42 healthy ones in the control group. BIA parameters that predict MS were assessed by dividing AN patients into groups by their hand grip strength test score (higher/lower than 22.5 kg).

Results: The highest accuracy for distinguishing AN subjects from the control group was achieved by cell membrane capacitance (AUC = 0.916), impedance at 200 kHz and 5 kHz ratio (AUC = 0.924), phase angle (PA) 5 kHz (AUC = 0.906) and PA 50 kHz (AUC = 0.919). The low MS group had significantly lower values of PA 50 kHz (mean: 4.03 ± 0.80° vs. 4.58 ± 0.65°;  = 0.032) and fat-free mass index (mean: 12.22 ± 1.41 kg/m vs. 13.14 ± 0.94 kg/m;  = 0.026). In the univariate model, PA 50 kHz ≥4.037° was associated with the lowest chance of muscle weakness (OR = 0.230;  = 0.005). In the multivariate analysis, PA 50 kHz was the only significant factor of MS (OR = 0.01;  = 0.027).

Conclusions: PA 50 kHz is the best BIA parameter to predict MS in AN patients. It could be useful for assessment before physical activity treatment application.