Comparison of three bioelectrical impedance methods with DXA in overweight and obese men

Objective: To compare bioelectrical impedance analysis (BIA) of body composition using three different methods against DXA in overweight and obese men. Research Methods and Procedures: Forty-three healthy overweight or obese men (ages 25 to 60 years; BMI, 28 to 43 kg/m²) underwent BIA assessment of body composition using the ImpediMed SFB7 (version 6; ImpediMed, Ltd., Eight Mile Plains, Queensland, Australia) in multifrequency mode (Imp-MF) and DF50 single-frequency mode (Imp-SF) and the Tanita UltimateScale (Tanita Corp., Tokyo, Japan). Validity was assessed by comparison against DXA using linear regression and limits of agreement analysis. Results: All three BIA methods showed good relative agreement with DXA [Imp-MF: fat mass (FM), r ² = 0.81; fat-free mass (FFM), r² = 0.81; percentage body fat (BF%), r² = 0.69; Imp-SF: FM, r² = 0.65; FFM, r ² = 0.76; BF%, r² = 0.40; Tanita: BF%, r² = 0.44; all p < 0.001]. Absolute agreement between DXA and Imp-MF was poor, as indicated by a large bias and wide limits of agreement (bias, ± 1.96 standard deviation; FM, -6.6 ± 7.7 kg; FFM, 8.0 ± 7.1 kg; BF%, -7.0 ± 6.6%). Imp-SF and Tanita exhibited a smaller bias but wide limits of agreement (Imp-SF: FM, -1.1 ± 8.5 kg; FFM, 2.5 ± 7.9 kg; BF%, -1.7 ± 7.3%; Tanita: BF%, 1.2 ± 9.5%). Discussion: Compared with DXA, Imp-MF produced large bias and wide limits of agreement, and its accuracy estimating body composition in overweight or obese men was poor. Imp-SF and Tanita demonstrated little bias and may be useful for group comparisons, but their utility for assessment of body composition in individuals is limited.