Understanding The Difference In Body Composition Assessment Methods In University Aged Canadian Students

Body composition is expressed as relative proportions of muscle, fat, bone, and other vital components of the body and is utilized as an overall health indicator. Body composition can be measured in several ways, including air displacement plethysmography (e.g., BOD POD) and Bioelectrical Impedance Analysis (BIA). To calculate body composition, the BOD POD measures body volume by changes in pressure in a closed chamber while the BIA measures the rate at which an electrical current travels through the body. The reasons for using different methods can depend on factors including time, cost, comfort, accessibility, and accuracy requirements. PURPOSE: The purpose of this study is to assess the accuracy of three different BIA devices in comparison to the BOD POD in healthy university aged Canadian students. METHODS: 617 undergraduate students (342 females and 275 males) with an age of (mean ± SD) 21.2 ± 2.0 years old, a height of 171.9 ± 9.9 cm, and a weight of 71.6 ± 15.2 kg completed the BOD POD, BIA Tanita BC-568, and BIA Tanita BF-683 body composition assessments. A 319 participant (187 females and 132 males) subsample with an age of 21.2 ± 1.8 years old, a height of 171.3 ± 9.4 cm, and a weight of 71.4 ± 15.0 kg also completed a BIA InBody test. Before all assessment measures, students were required to fast for two hours, refrain from exercise for six hours, not use diuretics for six hours, and void their bladder. Subjects completed their required assessments consecutively on the same day. RESULTS: Significant differences in body fat % (mean ± SD) were observed between the BOD POD (22.9 ± 9.0 %) and the Tanita-568 (21.6 ± 8.4 %, p < 0.0001), the Tanita-683 (22.4 ± 8.9%, p < 0.0001) and the InBody (23.1 ± 9.5, p < 0.05). The mean absolute error for each secondary measure was the following: Tanita-568 = 4.8%, Tanita-683 = 5.8% and the InBody = 4.6%. Bland-Altman plots demonstrated each secondary measure provided a positive bias whose 95% CI failed to overlap the line of equality. CONCLUSION: All secondary measures demonstrated significantly different results in comparison to the BOD POD. The InBody was the most accurate BIA device. Future research could investigate if the assessment from the various devices affects the body composition classifications based on body fat percentage.