Using an underwater weighing method to predict body fat is impractical for large field studies, requiring facilities and the cooperation of subjects and expertise of the investigators. Proxy anthropometric methods (Table 4.1) have been employed including skinfolds (2), body mass index (BMI) (3), and skinfolds combined with various body circumferences (4-6) to predict body fat estimated by underwater weighing. Body fat predicted from these equations shows high correlations with body fat measured by underwater weighing and relatively small errors of prediction. However, there have been few major validations of these equations in independent populations to test their generalizabil-ity or applicability in special population subgroups. The most widely used field method for total fat has been the four-skinfold methods (Figure 4.3), derived from underwater weighing (2). Recognizing possible errors of predicting body fat in subpopulations with altered fat distribution, regression equations including waist circumference (Figure 4.4) appear to have advantages in predicting total body fat by taking some account of this variation in fat distribution (6). Waist circumference, alone, predicts health (7) as well as body composition and is recommended for public health promotion (8,9).
Previously, little attention has been paid to developing an index of adiposity that could be used by lay people. The BMI has been the traditional index of obesity, but its concept and calculations are not readily understood by many. Criteria for classification of overweight and obesity have been inconsistent. Conventional classification of BMI, using the same criteria for both men and women, is based on life insurance and epidemiological data. Waaler (10) has shown a U-shaped relationship between BMI and mortality rates, with exponential increases of mortality in adult subjects with high BMI ( > 30 kg/m2) or low BMI ( < 20kg/m2). These cri
Measuring subcutaneous skinfold thicknesses at the sites of biceps, triceps, subscapular and suprailiac using skinfold
Measuring subcutaneous skinfold thicknesses at the sites of biceps, triceps, subscapular and suprailiac using skinfold teria for interpreting BMI do not apply to children, whose BMI is normally much lower than that of adults. The arbitrary cut-offs for overweight at BMI 25 and for obesity at BMI 30kg/m2 have now been adopted by the National Institutes of Health (8) in America and World Health Organization (11). These cut-offs have been used widely in Europe for many years.
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