THE RELATIONSHIP OF WEIGHT-HEIGHT INDEXES OF OBESITY TO BODY-FAT CONTENT

The measurement called desirable body weight (DBW) was derived by actuaries to indicate that weight which is associated with the lowest mortality. Percent deviation from DBW has become a standard measure of fatness. A different obesity index, body mass index (BMI), is weight in kilograms divided by the square of height in meters. Many workers consider both measures inferior to the measurement of body fat content (BFC). We compared the three measures of fatness in 40 men aged 18-50 and 48 women aged 21-47, ranging from nonobese to extremely obese. Total BFC was determined by isotope dilution of 3H-labeled water. DBWs used were those listed in the US Air Force Examination Manual of 1971; these approximate the midpoint of the range of medium-frame values in the 1959 Metropolitan Life Insurance Tables, but have the advantage of providing a single value for each height. We found nearly perfect correlation (r = 0.99, p < 0.001) between BMI and percent deviation from DBW in both men and women ranging from 14% below to 305% above DBW. Correlations between percent deviation from DBW and total BFC were extremely high: 0.95 (p < 0.001) for the men and 0.94 (p < 0.001) for the women, essentially the same as correlations between BMI and BFC, which were 0.96 (p < 0.001) for the men and 0.95 (p < 0.001) for the women. It appears that the two technically simple weight-height indices, BMI and percent deviation from DBW, give just as accurate a measurement of fatness as the technically complex measurement of total BFC. Of the two, percent deviation from DBW has the advantage of being conceptually simpler and intuitively understandable by nontechnical personnel.