Withers R T, Smith D A, Chatterton B E, Schultz C G, Gaffney R D
Exercise Physiology Laboratory, School of Education, Flinders University of South Australia, Adelaide.
Eur J Clin Nutr. 1992 Nov;46(11):773-84.
Comparisons were effected of the following four methods of estimating the percent body fat (%BF) of 12 highly trained male endurance athletes (mean +/- SD = 2.20 +/- 4.9 years, 176.8 +/- 5.9 cm 64.2 +/- 6.4 kg): underwater weighing (UWW), total body water (TBW), total body potassium (TBK) and dual-energy X-ray absorptiometry (DEXA). The DEXA mean of 6.8% BF was significantly less (P < 0.05) than those estimated via UWW: 9.7% BF; TBW: 10.6% BF (fat-free mass of FFM = 72.0% H2O); and TBK: 9.7% BF (FFM = 66.6 mmol K.kg-1). Nevertheless, the DEXA % BF correlated 0.746 and 0.737 (both P < 0.01) with those from UWW and TBW, respectively; these were the only correlation coefficients to attain statistical significance (P < or = 0.05). Despite the similar means for UWW, TBW and TBK, 12 of the 36 individual differences between these three methods ranged from 3.2 to 10.4% BF. A critical assumption of UWW, which is regarded by many as the criterion method for the estimation of % BF, is that the FFM has a density of 1.100 g.cm-3. Use of in vivo-measured TBW and bone mineral (via DEXA) for the computation of FFM densities for our subjects, while assuming that the two other components of the FFM (protein and non-bone mineral) remained constant, resulted in scores ranging from 1.09541 to 1.10246 g.cm-3 (mean +/- SD = 1.09881 +/- 0.00254 g.cm-3). FFM and % BF differences between use of a constant FFM density of 1.100 g.cm-3 and the individual values ranged from -1.02 to 0.57 kg (mean +/- SD = -0.28 +/- 0.60 kg) and from -0.9 to 1.7% BF (mean +/- SD = 0.5 +/- 0.9% BF), respectively. It may be concluded that with young male athletes: (1) use of constants based on normal male cadavers yielded similar group means for % BF determined by UWW, TBW and TBK but the DEXA % BF correlated significantly with those from UWW and TBW; and (2) in vivo measurements of individual differences in TBW and bone mineral support the use of conventional UWW for the estimation of % BF.
对12名训练有素的男性耐力运动员（平均±标准差=2.20±4.9岁，身高176.8±5.9厘米，体重64.2±6.4千克）的以下四种估算体脂百分比（%BF）的方法进行了比较：水下称重法（UWW）、总体水（TBW）、总身体钾（TBK）和双能X线吸收法（DEXA）。DEXA测得的平均体脂百分比为6.8%，显著低于通过UWW测得的9.7%BF、TBW测得的10.6%BF（无脂肪质量FFM=72.0%水）和TBK测得的9.7%BF（FFM=66.6 mmol K·kg-1）（P<0.05）。然而，DEXA测得的%BF与UWW和TBW测得的分别具有0.746和0.737的相关性（均P<0.01）；这是仅有的达到统计学显著性（P≤0.05）的相关系数。尽管UWW、TBW和TBK的平均值相似，但这三种方法之间36个个体差异中的12个在3.2%至10.4%BF之间。UWW的一个关键假设是，许多人将其视为估算%BF的标准方法，即FFM的密度为1.100 g·cm-3。对于我们的受试者，在假设FFM（蛋白质和非骨矿物质）的其他两个组成部分保持不变的情况下，使用体内测量的TBW和骨矿物质（通过DEXA）来计算FFM密度，得出的分数范围为1.09541至1.10246 g·cm-3（平均±标准差=1.09881±0.00254 g·cm-3）。使用1.100 g·cm-3的恒定FFM密度与个体值之间的FFM和%BF差异分别为-1.02至0.57千克（平均±标准差=-0.28±0.60千克）和-0.9至1.7%BF（平均±标准差=0.5±0.9%BF）。可以得出结论，对于年轻男性运动员：（1）使用基于正常男性尸体的常数，通过UWW、TBW和TBK测定的%BF得出的组均值相似，但DEXA测得的%BF与UWW和TBW测得的显著相关；（2）对TBW和骨矿物质个体差异的体内测量支持使用传统的UWW来估算%BF。
