The purpose of this study was to compare body fat estimates and fat-free mass (FFM) characteristics produced by multicompartment models when utilizing either dual energy X-ray absorptiometry (DXA) or single-frequency bioelectrical impedance analysis (SF-BIA) for bone mineral content (BMC) in a sample of physically active adults. Body fat percentage (BF%) was estimated with 5-compartment (5C), 4-compartment (4C), 3-compartment (3C), and 2-compartment (2C) models, and DXA. The 5C-Wang with DXA for BMC (i.e., 5C-WangDXA) was the criterion. 5C-Wang using SF-BIA for BMC (i.e., 5C-WangBIA), 4C-WangDXA (DXA for BMC), 4C-WangBIA (BIA for BMC), and 3C-Siri all produced values similar to 5C-WangDXA (r > 0.99; total error [TE] < 0.83%; standard error of estimate < 0.67%; 95% limits of agreement [LOAs] < ±1.35%). The 2C models (2C-Pace, 2C-Siri, and 2C-Brozek) and DXA each produced similar standard error of estimate and 95% LOAs (2.13%–3.12% and ±4.15%–6.14%, respectively). Furthermore, 3C-LohmanDXA (underwater weighing for body volume and DXA for BMC) and 3C-LohmanBIA (underwater weighing for body volume and SF-BIA for BMC) produced the largest 95% LOAs (±5.94%–8.63%). The FFM characteristics (i.e., FFM density, water/FFM, mineral/FFM, and protein/FFM) for 5C-WangDXA and 5C-WangBIA were each compared with the “reference body” cadavers of Brozek et al. 5C-WangBIA FFM density differed significantly from the “reference body” in women (1.103 ± 0.007 g/cm3; p < 0.001), but no differences were observed for 5C-WangDXA or either 5C model in men. Moreover, water/FFM and mineral/FFM were significantly lower in men and women when comparing 5C-WangDXA and 5C-WangBIA with the “reference body,” whereas protein/FFM was significantly higher (all p ≤ 0.001). 3C-LohmanBIA and 3C-LohmanDXA produced error similar to 2C models and DXA and are therefore not recommended multicompartment models. Although more advanced multicompartment models (e.g., 4C-Wang and 5C-Wang) can utilize BIA-derived BMC with minimal impact on body fat estimates, the increased accuracy of these models over 3C-Siri is minimal.
- Bioelectrical impedance analysis
- body fat percentage
- fat mass
- fat-free mass
- multicompartment models