BMI alone under-identifies obesity, particularly among Asian, Hispanic adults
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CHICAGO — BMI can underestimate obesity compared with body fat percentage determined by DXA scans, particularly among some racial and ethnic groups, according to data presented at ENDO 2023.
“Obesity is more prevalent in our society than estimated before,” Aayush Visaria, MD, MPH, an internal medicine resident physician at Rutgers Robert Wood Johnson Medical School, told Healio. “Nearly three in four young to middle-aged U.S. adults have obesity via total body fat percentage estimated from DXA scans, more than half of whom are incorrectly classified as having nonobese BMIs. There also exist significant racial/ethnic differences in body composition and body fat distribution, which will need to be further characterized in longitudinal studies.”
Using data from the 2011-2018 National Health and Nutrition Examination Survey, Visaria and colleagues identified nonpregnant U.S. adults aged 20 to 59 years who had whole-body DXA scans available. The researchers categorized participants by BMI into ethnicity-specific groups. Using whole-body DXA scans, the researchers calculated total body fat percentage, android-to-gynoid fat ratio and leg fat percentage for each participant. They estimated the odds of obesity by race or ethnicity using multivariable logistic regression.
Of the 9,784 participants (mean age, 39 years), 36% had obesity determined by BMI, and 74% had obesity determined by body fat percentage.
Asian American and Hispanic American adults with normal BMI were more likely to have obesity and more likely to have a greater proportion of abdominal fat than non-Hispanic white adults. However, non-Hispanic Black adults had a significantly lower likelihood of obesity determined by body fat percentage at normal or overweight BMI ranges and a lower proportion of abdominal fat, which suggests that BMI alone may not be sufficient to detect obesity, according to the researchers.
“Many clinicians likely have had this intuition that BMI is not a great indicator of obesity, but this is one of only a few studies to characterize this on a national scale,” Visaria said.
These findings suggest that BMI should be used in conjunction with other adiposity measures, such as waist circumference and other cardiovascular health markers, Visaria said.
“More research needs to be done to fully understand the discordance between BMI and true obesity and the implications it can have on health outcomes,” Visaria said. “Patients and providers should be aware that there exist racial/ethnic differences in body composition and body fat distribution with Hispanic and Asian individuals having more unfavorable parameters. They may benefit from other measures of adiposity like bioimpedance-based body fat percentage.”
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Visaria A, et al. Abstract OR10. Presented at: ENDO Annual Meeting; June 15-18, 2023; Chicago.
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