Johns Hopkins University researchers have found that nearly all adults identified as having obesity based on body mass index (BMI) also had confirmed excess adiposity.
Use of BMI to diagnose obesity has become increasingly controversial. BMI does not distinguish between
body fat, muscle, and bone mass, raising concerns that obesity may be overdiagnosed. An expert commission recently recommended that clinical assessments of obesity should be confirmed by direct body fat measurement or BMI and at least one other anthropometric index.
In a research letter, "Prevalence of Obesity With and Without Confirmation of Excess Adiposity Among US Adults,"
published in
JAMA, researchers analyzed data from a
cross-sectional survey to assess
obesity prevalence using both BMI and confirmatory measures of body fat.
Researchers evaluated data from 2,225 adults aged 20 to 59 years participating in the 2017–2018 National Health and Nutrition Examination Survey (NHANES). The survey included standardized measurements of height, weight, and
waist circumference, along with whole-body dual-energy X-ray absorptiometry (DEXA) to determine body fat percentages.
Participants with an elevated BMI and either an elevated waist circumference, elevated body fat percentage, or a BMI of 40 or greater were considered to have confirmed excess
adiposity. BMI thresholds were adjusted by race and ethnicity, with obesity defined as a BMI of 30 or higher for most participants, and 27.5 or higher for non-Hispanic Asian individuals.
When only considering BMI, 39.7% met the definition of obesity. When using BMI in conjunction with criteria for excess adiposity confirmation, prevalence dropped ever so slightly to 39.1%.
Overall, 98.4% of persons with obesity based on BMI had confirmed excess adiposity.
Results were consistent across age, sex, and racial and
ethnic groups. Prevalence remained the same when confirmed excess adiposity was defined using either elevated waist circumference or body fat measured by DEXA.