Submitted to: British Journal of Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/5/2009
Publication Date: 10/1/2009
Citation: Jackson, A.S., Ellis, K.J., McFarlin, B.K., Sailors, M.H., Bray, M.S. 2009. Body mass index bias in defining obesity of diverse young adults: The Training Intervention and Genetics of Exercise Response (TIGER) Study. British Journal of Nutrition. 102(7):1084-1090. Interpretive Summary: The body mass index is universally used to identify obesity in adults of all ethnicities, although it was originally established using only older Caucasians or non-minority populations. When we examined multi-ethnic, college-aged young adults, we found that there were significant differences in the amount of body fat with ethnicity and gender for the same body-size index when compared with the Caucasians. If the standard index is used, the amount of body fat would be overestimated for African-Americans, while underestimated for Asian-Americans. We have proposed ethnic-specific adjustments for the body-size index that will allow for the generalizability of the basic weight-for-height index.
Technical Abstract: The BMI cut-score used to define overweight and obesity was derived primarily using data from Caucasian men and women. The present study evaluated the racial/ethnic bias of BMI to estimate the adiposity of young men and women (aged 17–35 years) using dual-energy X-ray absorptiometry (DXA) determination of percentage body fat (DXA-BF%) as the referent standard. The samples were 806 women and 509 men who were tested from one to three times over 9 months, providing 1300 observations for women and 820 observations for men. Linear mixed models (LMM) regression showed that with age and BMI controlled, DXA-BF% of African-American (AA) men and women, Asian-Indian men and women, Hispanic women, and Asian women significantly differed from non-Hispanic white (NHW) men and women. For the same BMI of NHW women, the DXA-BF% of AA women was 1.76% lower, but higher for Hispanic (1.65%), Asian (2.65%), and Asian-Indian (5.98%) women. For the same BMI of NHW men, DXA-BF% of AA men was 4.59% lower and 4.29% higher for Asian-Indian men. Using the recommended BMI cut-scores to define overweight and obesity systematically overestimated overweight and obesity prevalence for AA men and women, and underestimated prevalence for Asian-Indian men and women, Asian women, and Hispanic women. The present study extends the generalizability of research documenting the racial/ethnic bias of the universal overweight and obesity BMI cut-scores.