Validation of body composition estimates in male and female distance runners using estimates from a four-component model

This study used estimates of body composition from a four-component model (%Fat_d,w,m) to determine whether the assumed density (D_ffm) and the composition of the fat-free mass (FFM), and estimates of body composition from methods based on two- and three-component models are valid in distance runners. Measures of body density (D_b) by underwater weighing, total body water by deuterium dilution, and bone mineral by dual-energy X-ray absorptiometry (DXA) were obtained in 10 female and 12 male runners and an equal number of controls matched for age, height, weight, gender, and ethnicity. D_ffm of the runners did not differ from 1.1 g·cm⁻³ or from the controls even though the composition of the FFM differed from that assumed. Therefore, percentage of body fat (%Fat) from densitometry did not differ from %Fat_d,w,m in the runners, although individual variation was substantial (−5.3 to 3.0% body mass, SD_diff = 2.1% body mass). Three-component model estimates of %Fat from D_b and body water agreed quite closely with %Fat_d,w,m (x ≤ 1.6% body mass, SD_diff = 0.5% body mass), whereas those from D_b and body mineral (x _diff = 1.6–2.9% body mass, SD_diff = 2.3% body mass) and from DXA (x _diff = 2.2–4.0% body mass, SD_diff = 2.1% body mass) were less accurate and underestimated %Fat_d,w,m. We conclude that D_ffm does not differ from 1.1 g·cm⁻³ and that densitometry is a valid method to estimate group mean body composition, but that measurement of D_b and total body water are necessary for accurate individual estimates of body composition in male and female distance runners. Am. J. Hum. Biol. 12:301–314, 2000. © 2000 Wiley-Liss, Inc.