OR10-01 Discordance Between Body Mass Index and Dual-energy X-ray Absorptiometry Based Adiposity Measures Among United States Adults
Authors: Visaria Aayush , Sindhu Trisha , Dharamdasani Tina 
Published: October 2023

Disclosure: A. Visaria: None. T. Sindhu: None. T. Dharamdasani: None.

Background: Body Mass Index (BMI) is a widely used, albeit flawed, surrogate measure for adiposity. Whether the extent of discordance between BMI, true adiposity, and body fat distribution is different by race is unknown. We sought to describe the racial differences in BMI and dual-energy x-ray absorptiometry (DEXA) based adiposity measures among a nationally representative sample of adults. Methods: We identified non-pregnant U.S. adults 20-59 years from the 2011-2018 National Health and Nutrition Examination Survey (NHANES) with whole body DEXA scan data. BMI was categorized into ethnicity-specific (non-Asian: underweight&lt;18.5, normal=18.5-24.9, overweight=25-29.9, obese≥30 kg/m2, Asian: &lt;18.5, 18.5-22.9, 23-27.4, 27.5+) categories. DEXA scans were performed using Hologic Discovery densitometers, analyzed by Hologic software (APEX v4.0), and verified by expert reviewers. Total body fat % (BF%), android-to-gynoid fat ratio, and leg fat % (% of total BF in legs) were calculated. Among adults classified as normal/overweight via BMI, we estimated odds of obesity (BF% ≥25% in male, ≥32% in female) by race (non-Hispanic White [NHW], non-Hispanic Black [NHB], Asian, Hispanic, and Other) using multivariable logistic regression. We estimated mean DEXA adiposity measures by race using multivariable linear regression. Analyses were adjusted for confounders & the survey design. Results: Among 9,784 participants (mean age 39y [SD, 11], 61% NHW, 49% female), 36% had BMI≥30 and 74% had obesity per BF%. Among normal BMI adults, 44% of NHW, 27% of NHB, 49% of Hispanic, and 49% of Asians had obesity as per BF% (p&lt;0.001). Among overweight BMI adults, the adjusted mean (SE) android-to-gynoid fat ratio was 1.01 (0.01) for NHW, 0.97 (0.01) for NHB, 1.05 (0.01) for Hispanics, and 1.04 (0.01) for Asians (p&lt;0.001). Among normal BMI adults, the adjusted mean (SE) android-to-gynoid fat ratio was 0.84 (0.01) for NHW, 0.85 (0.01) for NHB, 0.89 (0.01) for Hispanics, and 0.91 (0.01) for Asians (p&lt;0.001 for NHW vs. Asian, Hispanic). The adjusted mean leg fat % was 39.2% (0.1) for NHW, 40.9% (0.2) for NHB, 37.3% (0.2%) for Hispanics, and 36.7% (0.2) for Asians (p&lt;0.001), Overweight BMI NHBs had 58% lower odds of obesity compared to NHW (aOR [95% CI]; NHB: 0.42 [0.32, 0.54], Hispanic: 1.26 [0.97, 1.64], Asian: 0.81 [0.63, 1.05]). Conclusion: Nearly 3 in 4 young-to-middle-aged U.S. adults have obesity via total body fat percentage estimated from DEXA scans. Despite ethnicity-specific BMI cutoffs, normal BMI Asian Americans, as well as Hispanics, were more likely to have obesity, and more likely to have a greater proportion of abdominal fat than NHW. On the other hand, NHB had significantly lower likelihood of obesity at normal/overweight BMI ranges, and lower proportion of abdominal fat. These suggest that BMI alone may not be sufficient to detect metabolically unhealthy adiposity, especially in Asian Americans and Hispanics.

Presentation: Friday, June 16, 2023