The effect of sex, age and race on estimating percentage body fat from body mass index: The Heritage Family Study

A. S. Jackson, P. R. Stanforth, J. Gagnon, T. Rankinen, A. S. Leon, D. C. Rao, J. S. Skinner, C. Bouchard, J. H. Wilmore

Research output: Contribution to journalArticlepeer-review

426 Scopus citations

Abstract

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 65y. 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.

Original languageEnglish
Pages (from-to)789-796
Number of pages8
JournalInternational Journal of Obesity
Volume26
Issue number6
DOIs
StatePublished - 2002

Keywords

  • Body composition
  • Body mass index
  • Obese
  • Overweight

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