Snead D B, Birge S J, Kohrt W M
Section of Applied Physiology, Washington University School of Medicine, St. Louis, Missouri 63110.
J Appl Physiol (1985). 1993 Feb;74(2):770-5. doi: 10.1152/jappl.1993.74.2.770.
To determine whether percent body fat (%BF) is overestimated in older people by hydrodensitometry (HD) because of an age-related decrease in bone mineral content (BMC), body composition of 113 women and 72 men (21-81 yr) was assessed by HD and dual-energy X-ray absorptiometry (DEXA). DEXA provides an estimate of %BF adjusted for differences in BMC. HD %BF and DEXA %BF were not different in young people [21-39 yr; 17.6 +/- 6.4 (SD) vs. 17.6 +/- 7.2%, NS], were slightly, but significantly, different in middle-aged people (40-59 yr; 25.5 +/- 6.4 vs. 24.1 +/- 6.7%, P < 0.05), and showed the largest disparity in older people (> or = 60 yr; 34.9 +/- 7.9 vs. 30.8 +/- 8.7%, P < 0.05). The discrepancy in older people was apparently not due to mineral loss, however, inasmuch as correction of HD %BF for variance in BMC as a fraction of fat-free mass resulted in only small adjustments (approximately 1%) of %BF. Assessment of DEXA %BF was further evaluated in nine subjects with packets of lard (2-3 kg) overlying either the thigh or the trunk region. Only 55% of the exogenous fat was identified as fat when it was in the trunk region compared with 96% when it was positioned over the legs. These data suggest that the age-related increase in upper body adipose tissue is underestimated by DEXA.
为了确定由于骨矿物质含量（BMC）随年龄增长而下降，通过水下密度测量法（HD）测量老年人的体脂百分比（%BF）是否会被高估，采用HD和双能X线吸收法（DEXA）对113名女性和72名男性（21 - 81岁）的身体成分进行了评估。DEXA可提供针对BMC差异进行调整后的%BF估计值。年轻人（21 - 39岁）中，HD %BF和DEXA %BF无差异[分别为17.6±6.4（标准差）与17.6±7.2%，无显著性差异（NS）]；中年人（40 - 59岁）中，二者略有差异但具有显著性（分别为25.5±6.4与24.1±6.7%，P < 0.05）；老年人（≥60岁）中，差异最为显著（分别为34.9±7.9与30.8±8.7%，P < 0.05）。然而，老年人中的差异显然并非由于矿物质流失，因为将HD %BF校正为BMC作为去脂体重的一部分的方差后，%BF的调整幅度很小（约1%）。在9名受试者的大腿或躯干区域覆盖猪油包（2 - 3千克），进一步评估DEXA %BF。当外源性脂肪位于躯干区域时，只有55%被识别为脂肪，而位于腿部时这一比例为96%。这些数据表明，DEXA低估了与年龄相关的上身脂肪组织增加。
