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Research Project: Childhood Obesity Prevention

Location: Children's Nutrition Research Center

Title: Relationship between body fat and BMI in a U.S. Hispanic population-based cohort study: Results from HCHS/SOL

item WONG, WILLIAM - Children'S Nutrition Research Center (CNRC)
item STRIZICH, GARRETT - Albert Einstein College Of Medicine
item HEO, MOONSEONG - Albert Einstein College Of Medicine

Submitted to: Obesity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2016
Publication Date: 5/17/2016
Citation: Wong, W.W., Strizich, G., Heo, M., et al. 2016. Relationship between body fat and BMI in a U.S. Hispanic population-based cohort study: Results from HCHS/SOL. Obesity. doi: 10.1002/oby.21495.

Interpretive Summary: Body mass index (BMI) is used routinely to find out if some one is normal weight, overweight or obese because it can be calculated simply. However, in a national study of adults, BMI was found to put many overweight and obese adults into the normal weight group based on actual body fat data. The non-Mexican Hispanic/Latino group is a large and growing minority in the United States with higher rates of obesity and diabetes than whites. However, the ability of BMI to define the weight status among Latinos is not known. In a national study of 16,415 Latinos with Central American, Cuban, Dominican, Mexican, Puerto Rican, and South American backgrounds, we tested how well BMI could define the weight status among Latinos when compared to actual body fat data. We learned that BMI was not related to percentage of body fat in a straight-line manner. However, the inverse of BMI was related in a straight-line manner with percentage of body fat. Based on this relationship, we found that BMI also put many overweight and obese non-Mexican Latinos into the normal weight group especially among the younger Latinos and women. Therefore, the use of BMI greatly underestimated the number of Latinos with excess body fat and could underestimate the link between body fat and obesity-related risks among Latinos.

Technical Abstract: To evaluate the percentage of body fat (%BF)-BMI relationship, identify %BF levels corresponding to adult BMI cut points, and examine %BF-BMI agreement in a diverse Hispanic/Latino population. %BF by bioelectrical impedance analysis was corrected against %BF by 18O dilution in 434 participants of the ancillary Hispanic Community Health Study/Study of Latinos. Corrected %BF was regressed against 1/BMI in the parent study (n = 15,261), fitting models for each age group, by sex, and Hispanic/Latino background; predicted %BF was then computed for each BMI cut point. Bioelectrical impedance analysis underestimated %BF by 8.7'+/-'0.3% in women and 4.6'+/-'0.3% in men (P'<'0.0001). The %BF-BMI relationship was nonlinear and linear for 1/BMI. Sex- and age-specific regression parameters between %BF and 1/BMI were consistent across Hispanic/Latino backgrounds (P'>'0.05). The precision of the %BF-1/BMI association weakened with increasing age in men but not women. The proportion of participants classified as nonobese by BMI but as having obesity by %BF was generally higher among women and older adults (16.4% in women vs. 12.0% in men aged 50-74 years). %BF was linearly related to 1/BMI with consistent relationship across Hispanic/Latino backgrounds. BMI cut points consistently underestimated the proportion of Hispanics/Latinos with excess adiposity.