[Comparison of bioelectrical impedance analysis and isotope dilution method in assessment of body composition]

To determine the validity of bioelectrical impedance analysis (BIA) in measuring body composition and to compare with the reference stable isotope dilution method.

According to the data from 150 students of Bethune Military Medical College, 16 female young adults with normal BMI were selected as the participants. The experimental period was 14 days. During the experimental period, the subjects were centralized on management. At the first day of the period, double labeled water was given to the subjects orally. The urine collection time-points were 2h, 4h, 6h, 8h and the 2nd to 14th day after the administration of isotope dose. All isotope measurements were made by using an isotope ratio mass spectrometer. From the isotope curing curve, the indexes of body composition were gained. At the same time, the body compositions were also measured by using BIA method every day (3 hours after dinner). The paired t test and Pearson correlations were used to measure the significance and the degree of correlation between the measurements determined by using the two methods.

There were no significant differences between the measurements determined by using the two methods. TBW, FFM, BF and BF% measured with the BIA method were significantly correlated with those measured by using the isotope method (r = 0.556, 0.556, 0.817 and 0.606 respectively).

BIA might provide an accurate and reliable assessment in body composition of the healthy Chinese adults.