Reliability and Agreement of Various InBody Body Composition Analyzers as Compared to Dual-Energy X-Ray Absorptiometry in Healthy Men and Women

Background: Bioelectrical impedance analysis has evolved over the years to include the use of multiple frequencies and impedance measurements to improve the accuracy and reliability of body composition estimates. The purpose of this investigation was to evaluate the reliability of the InBody230, InBody720, and InBody770 to measure body fat percent (BF%), fat mass (FM), and fat-free mass (FFM) in the general population and to compare results to dual-energy X-ray absorptiometry (DXA). Methods: A total of 31 males and 36 females participated in 2 d of testing separated by 24-72 h. Each visit consisted of a DXA scan, and analysis with the InBody(230), InBody(720), and InBody(770). Results: All 3 bioelectrical impedance devices (InBody(230), InBody(720), and InBody(770)) were reliable in men and women as indicated by high intraclass correlation coefficients for BF% (>= 0.98), FM (>= 0.98), and FFM (>= 0.99) and low standard error of measurement for BF% (0.77%-0.99%), FM (0.54-0.87 kg), and FFM (0.58-0.84 kg) and minimum difference for BF% (2.12%-2.73%), FM (1.49-2.39 kg), and FFM (1.60-2.32 kg), respectively. When examining the agreement between the 3 InBody analyzers with DXA, systematic bias (underestimation of BF% and FM and overestimation of FFM) was present for all comparisons (p < 0.05) while proportional bias was present for FM in women and FFM in men. However, there was small individual error for all comparisons as indicated by the standard error of estimate and 95% limits of agreement. Conclusion: The InBody analyzers produce small individual error, which suggest these methods can be used as a surrogate when DXA is not available; however, practitioners should be aware of the systematic bias for all comparisons and proportional bias for FM in women and FFM in men. Furthermore, findings revealed that the research grade models, InBody(720) and InBody(770), added minimal benefit over the portable InBody(230) when assessing BF%, FM, and FFM.