Ethnic and age trends for body composition in women residing in the U.S. Southwest: II. Total fat

This study assessed body density (BD) in an ethnically diverse sample of women (African American, Caucasian, Mexican American and Native American) (N = 139) who were between 20 and 30 or 40 and 50 yr of age and of normal weight for their height. BD was assessed using three methods: hydrostatically determined density (UWW), total body potassium (TBK) and the Jackson et al. (1980) sum of seven SF with gluteal circumference (SF). Ethnic differences in BD were detected by TBK and UWW. BD from SF did not detect ethnic differences, and the SEE was unacceptable. Based on multiple regression, the prediction equation was: BD = 1.1197794 - 0.000224382 (x₃) + 0.006999 (e2) - 0.000320177 (x₂) - 0.001892 (e1) + 0.001750 (e3) - 0.000537005 (x₁) (where x₁ = gluteal C, x₂ = age in years, x₃ = sum of 7 SF and e1, e2, and e3 describe ethnicity). This formula had a reduced SEE, a higher correlation with hydrostatically determined BD, and was sensitive to ethnic differences detected with other measures of BD. A 24-mmol decrease in potassium was found when comparing the older Caucasian women with the younger Caucasian women, while the difference for the African, Mexican, and Native American groups was 200-300 mmol.