BODY-FAT AND MUSCLE THICKNESS IN JAPANESE AND CAUCASIAN FEMALES

Fat and muscle thicknesses; were measured at eight sites by B-mode ult rasonography on 36 Japanese (age = 25.9 +/- 1.9 years; mean +/- SD) an d 56 Caucasian females (25 +/- 2 years) to compare the distribution of these tissues. The eight sites were the biceps, triceps, forearm, sub scapular, abdomen, quadriceps, hamstring, and calf. Hydrostatically de termined body density, corrected for residual lung volume, was similar (P > 0.05) for Japanese (1.048 +/- 0.008 g . ml(-1)) and Caucasians ( 1.050 +/- 0.009 g . ml(-1)). However, in part because of their greater body mass, Caucasians had significantly more (P < 0.05) fat mass (FM; 12.5 +/- 3.2 kg) and fat-free mass (FFM; 45.1 +/- 5.1 kg) compared to the Japanese (FM = 11.1 +/- 2.3 kg, FFM = 38.0 +/- 3.5 kg). From the results of a subsample analysis of a group matched for stature and bod y mass, Japanese women had a greater abdominal fat thickness than Cauc asians, but had less fat thickness at the triceps and hamstring sites. Caucasians had greater muscle thicknesses than Japanese at all sites except for abdomen, hamstring, and calf. The ratio of fat thickness to FM . stature(-2) was higher on the trunk (P < 0.001) in Japanese (6.6 50 +/- 1.721 mm(3) . g(-1) x 10(3)) than in Caucasians (4.713 +/- 1.44 1 mm(3) . g(-1) x 10(3)). The ratio of muscle thickness to FFM . statu re(2) was higher (P < 0.001) in Caucasians than in Japanese at the upp er-extremity and trunk sites. These results suggest that the distribut ion of subcutaneous fat might be specific to ethnic origin, and that J apanese women have less muscle development than Caucasians even when m atched for stature and body mass. (C) 1994 Wiley-Liss, Inc.