25 kg/m², a view adopted in this report. Although the healthy BMI range is the result of a consensus, there are reasons to suggest that slightly different mortality-based BMI ranges may be appropriate for different populations (NHLBI/NIDDK, 1998).

In establishing the 2000 Dietary Guidelines, the U.S. Departments of Agriculture and of Health and Human Services set the “healthy weight” upper limit at a BMI of 24.99 kg/m² for adult men and women because mortality increases significantly beyond this point (USDA/HHS, 2000). Although the incidence of diabetes, hypertension, and coronary heart disease begins to increase even below this cutoff, a BMI of 24.99 kg/m² is considered a reasonable upper limit of healthy weight. The lower BMI limit of 18.5 kg/m² is not as well substantiated. The point at which low BMI poses a health risk is poorly defined. The ability to identify persons with low BMIs who are at increased risk for morbidity and mortality is highly nonspecific.

Reference Weights. Weights corresponding to BMIs from 18.5 up to 25 kg/m² are tabulated for adult men and women with heights ranging from 1.47 to 1.98 m in Table 5-3 (men) and Table 5-4 (women). Reference weights used in this report correspond to a BMI of 22.5 kg/m² for men and a BMI of 21.5 kg/m² for women, which match the 50th percentile among 19-year-old individuals (Kuczmarski et al., 2000).

Relationship Between BMI and Body Fat Content. The Third National Health and Nutrition Examination Survey (NHANES III) data that provide the major anthropometric parameters, including waist circumference, skin-fold measurements, and bioimpedance data for some 15,000 women and men were examined to evaluate the body fat content typical for all BMI values (Appendix Table H-1) and among the 5,700 women and men whose BMIs were from 18.5 up to 25 kg/m² (Appendix Table H-2). Bioimpedance data were used to calculate percent body fat using equations developed by Sun and coworkers (2003).

The regressions of percent body fat versus BMI (Appendix Table H-3) were used to define the percent body fat ranges given in Table 5-5. The multiple regressions of percent body fat versus BMI and waist circumference (Appendix Table H-4) and of percent body fat versus BMI and triceps skinfold (Appendix Table H-5) were used to construct Figures 5-3 and 5-4.

One of the most commonly cited problems encountered in using BMI as a criterion for assessing the presence of excess body fat is that muscular subjects may have a BMI greater than 25 kg/m² without carrying excess body fat. In such cases, it is helpful to consider waist circumference in addition to BMI. As shown in Figure 5-3, a man with a BMI of 30 kg/m²