OBJECTIVE: To study the effects of sex, age and race on the relation between body mass index (BMI) and measured percent body fat (%fat). DESIGN: Cross-sectional validation study of sedentary individuals. SUBJECTS: The Heritage Family Study cohort of 665 black and white men and women who ranged in age from 17 to 65 y. MEASUREMENTS: Body density determined from hydrostatic weighing. Percentage body fat determined with gender and race-specific, two-compartment models. BMI determined from height and weight, and sex and race in dummy coded form. RESULTS: Polynomial regression showed that the relationship between %fat and BMI was quadratic for both men and women. A natural log transformation of BMI adjusted for the non-linearity. Test for homogeneity of log transformed BMI and gender showed that the male-female slopes were within random variance, but the intercepts differed. For the same BMI, the %fat of females was 10.4% higher than that of males. General linear models analysis of the women's data showed that age, race and race-by-BMI interaction were independently related to %fat. The same analysis applied to the men's data showed that %fat was not just a function of BMI, but also age and age-by-BMI interaction. Multiple regression analyses provided models that defined the bias. CONCLUSIONS: These data and results published in the literature show that BMI and %fat relationship are not independent of age and gender. These data showed a race effect for women, but not men. The failure to adjust for these sources of bias resulted in substantial differences in the proportion of subjects defined as obese by measured %fat.
OBJECTIVE: To study the effects of sex, age and race on the relation between body mass index (BMI) and measured percent body fat (%fat). DESIGN: Cross-sectional validation study of sedentary individuals. SUBJECTS: The Heritage Family Study cohort of 665 black and white men and women who ranged in age from 17 to 65 y. MEASUREMENTS: Body density determined from hydrostatic weighing. Percentage body fat determined with gender and race-specific, two-compartment models. BMI determined from height and weight, and sex and race in dummy coded form. RESULTS: Polynomial regression showed that the relationship between %fat and BMI was quadratic for both men and women. A natural log transformation of BMI adjusted for the non-linearity. Test for homogeneity of log transformed BMI and gender showed that the male-female slopes were within random variance, but the intercepts differed. For the same BMI, the %fat of females was 10.4% higher than that of males. General linear models analysis of the women's data showed that age, race and race-by-BMI interaction were independently related to %fat. The same analysis applied to the men's data showed that %fat was not just a function of BMI, but also age and age-by-BMI interaction. Multiple regression analyses provided models that defined the bias. CONCLUSIONS: These data and results published in the literature show that BMI and %fat relationship are not independent of age and gender. These data showed a race effect for women, but not men. The failure to adjust for these sources of bias resulted in substantial differences in the proportion of subjects defined as obese by measured %fat.
Authors: Mee-Ri Lee; Jin Hee Kim; Yoon-Hyeong Choi; Sanghyuk Bae; Choonghee Park; Yun-Chul Hong Journal: Environ Sci Pollut Res Int Date: 2015-01-21 Impact factor: 4.223
Authors: Monique E Spencer; Alka Jain; Amy Matteini; Brock A Beamer; Nae-Yuh Wang; Sean X Leng; Naresh M Punjabi; Jeremy D Walston; Neal S Fedarko Journal: J Gerontol A Biol Sci Med Sci Date: 2010-05-17 Impact factor: 6.053
Authors: BongKyoo Choi; Dale Steiss; Javier Garcia-Rivas; Stacey Kojaku; Peter Schnall; Marnie Dobson; Dean Baker Journal: Int Arch Occup Environ Health Date: 2015-08-08 Impact factor: 3.015