OBJECTIVE: The purpose of this study was to compare skinfold thickness (SKF) and bioelectrical impedance analysis (BIA) of body composition using three different equations against dual-energy X-ray absorptiometry (DXA) in overweight and obese Brazilian women. SUBJECTS AND METHOD: Thirty-four women (age 43.8 ± 10.9 years; body mass index [BMI] 32.1 ± 4.3 kg/m²) had percentage body fat (BF%), fat mass (FM) and fat-free mass (FFM) estimated by DXA, SKF and BIA (BIA-man: manufacturer's equation; and predictive obesity-specific equations of Segal and of Gray). Regression analysis, Bland-Altman plot analysis and intra-class correlation coefficient (ICC) were used to compare methods. RESULTS: Absolute agreement between DXA and BIA-man was poor for all measures of body composition (BF% -6.8% ± 3.7%, FM -3.1 ± 3.6 kg, FFM 5.7 ± 2.8 kg). BIA-Segal equation showed good absolute agreement with DXA for BF% (1.5% ± 1.5%), FM (1.0 ± 3.2 kg) and FFM (1.5 ± 2.6 kg), albeit the limits of agreement were wide. BIA-Gray equation showed good absolute agreement with DXA for FM (2.3 ± 4.1 kg), and smaller biases for BF% (0.05% ± 4.4%) and FFM (0.2 ± 2.9 kg), although wide limits of agreement. BIA-Gray and DXA showed the highest ICC among the pairs of methods. A good absolute agreement was observed between DXA and SKF for BF% (-2.3% ± 5.8%), FM (0.09 ± 4.7 kg), and FFM (2.4 ± 4.4 kg), although limits of agreement were wider and ICC between DXA and SKF for BF% indicated poor degree of reproducibility. CONCLUSION: These findings show that both BIA-Segal and BIA-Gray equations are suitable for BF%, FM and FFM estimations in overweight and obese women.
Absorptiometry, photon; electric impedance; skinfold thickness; body composition; obesity; overweight