Estimation of body fat from ultrasound measures of subcutaneous fat and circumferences in obese women.

Body density and body fat are commonly estimated from measures of subcutaneous adipose tissue taken with skinfold calipers at specific body sites. In obese individuals, factors such as compression and inability to palpate tissues hinder the accurate measurement of skinfolds. Thus, the use of skinfold caliper measurements may yield spurious body density values. Previous research indicated that in obese persons, subcutaneous adipose tissue thickness measured by ultrasound gave more accurate predictions of body density, determined by hydrostatic weighing, than did caliper measurements. The present study compared ultrasound with circumference readings in estimating the body density of 31 white, obese women. Subcutaneous adipose tissue was measured at six body sites with an ADR model 2130 ultrasound real-time scanner. A calibrated fiberglass tape was used to take circumferences at ten body sites. Body density was computed from hydrostatic weighing using the Goldman/Buskirk formula, and percentage body fat, from the Siri equation. Mean (+/- s.d.) body density was 1.002 (+/- 0.015) g/ml, percentage body fat, 44.0 (+/- 7.5) and body mass index, 32.3 (+/- 4.5). The best prediction of body density, as determined by hydrostatic weighing, was with biceps and mid-thigh sites for ultrasound (r2 = 0.569). The combination of age, wrist, waist and upper thigh sites gave the best prediction for circumferences (r2 = 0.752). For the obese women in this study, circumference measurements provided a better estimation of body density and hence, body fat, than did ultrasound measures. A possible explanation to account for the difference is that circumference measures reflect both internal and subcutaneous adipose tissue, while only subcutaneous adipose tissue is measured with ultrasound.