DIFFERENCES IN BODY FAT PERCENTAGE MEASURED USING DUAL ENERGY X-RAY ABSORPTIOMETRY AND THE BOD POD IN 100 WOMEN

Abstract

This study was conducted to determine the extent to which body fat percentage (BF%) obtained using the Bod Pod (Pod) differs from BF% derived using Dual Energy X-ray Absorptiometry (DXA) in 100 women ages 35–45 years. Each subject was tested in a one-piece nylon swim suit and a lycra cap was used for all subjects in the Pod. Subjects were first tested in the Bod Pod (Life Measurement Instruments) and then using DXA (Model 4500W, Hologic). Subjects were given a short break between each test and retest. For the Pod assessment, subjects were tested until two BF% measures were within 1% point of each other, then the average of the two measures was used. Lung volume was measured for the first Pod test and the same lung volume was used for subsequent tests. With DXA, only two measurements were taken and the average used no matter the difference between the two measures. Results showed that the mean BF% for the Pod was 30.78 ± 7.92 and 30.35 ± 7.23 for DXA (mean difference = 0.43 ± 2.76; p > 0.05). The mean of the sum of the absolute value of the differences between the DXA and Pod results was 2.06. A total of 85% of the subjects had a mean difference between their Pod and DXA results of less than 4% points; 77% had a difference of less than 3% points; 63% had a mean difference of less than 2% points; and 36% had a mean difference between the two measures of less than 1% point. The Pearson correlation between the Pod and DXA BF% results was 0.94 (p < 0.001) and the intraclass correlation was 0.97 (p < 0.001). When a regression equation was generated using Pod results to predict DXA results, the standard error of estimate (SEE) was 2.5%. Apparently, the Pod and DXA methods produce statistically equal BF% results with most subjects showing less than 2% points difference between the two assessments.