Using Criteria Method To Validate Bia On Body Composition Assessment

Human body composition is one branch of biology, one of which is toexplore the method of measuring body composition in vivo. Bodycomposition can be measured by many techniques. Isotope dilution methodand bioelectrical impedance analysis (BIA) are both based on atwo-component model (2C), in which the body is divided into fat mass (FM)and fat free mass (FFM). Moreover, the method of DXA is based on athree-compartment model (3C), in which the FFM is composed of lean softtissue (LST) and bone mass.The main principle of BIA is dependent on Ohm’s law, using differentbody static and dynamic resistance characteristics, which is combined withthe laws of the relevant biological characteristics of body composition,density, age, race, gender and so on. The doubly labeled water (DLW)made up2H and18O. In this study the method of DLW is used to measurethe total body water (TBW) of Chinese young adults in designed conditions,and then to calculate the fat free mass (FFM), fat mass (FM) and FM%byformula. Difference between the two methods (DLW and BIA) is compared,and corrected linear equation is established. After fasting4hours, all thesubjects received a whole body MRI scan. The dlcom image processingsoftware is used to measure the weight of all levels of adipose tissue, andthen the mass and weight of total fat are calculated according to the image.Difference of fat mass between the two methods (MRI and BIA) iscompared, and corrected linear equation is established. With DXA bonemeasurement as a standard method, the result from BIA is compared andanother corrected liner equation is established.Twelve healthy college-aged (23.6±1.4ys) men and women (BMI, 21.5±1.5) were enrolled in the study. The body compositions determined by18O and2H were of no statistically difference. Taking the2H as the TBWcriteria results, the TBW, FFM, FM and FM%obtained by BIA weresignificantly correlated with those measured by the isotope dilution(2H)(r=0.959,0.959,0.563,0.780, respectively). The simple linear regressionequation for TBW between the two was y=4.057+0.798x (r2=0.917，P<0.001). The difference of Bland-Altman is (-3.1±4.4) kg. Taking theMRI as the fat mass criteria metho, the FM obtained by BIA wassignificantly correlated with the result of MRI (r=0.924). The simple linearregression equation for FM between the two was y=1.01x+0.97(r2=0.840, P <0.001). The difference of Bland-Altman is (1.0±2.0) kg. Takingthe DXA as bone mass criteria method, the bone mass obtained by the BIAwere significantly correlated with those measured by the DXA (r=0.952).The simple linear regression equation for TBW between the two wasy=0.76x+0.03（r2=0.897，P <0.001）. The difference of Bland-Altman is(-0.70±0.34) kg.BIA is comparable to isotope dilution, MRI and DXA on bodycomposition assessment. The results of BIA are reliable and BIA can beused as an easy and good tool to evaluate the TBW, FM, BM and FFM inChinese population.