A recent study published in JAMA has found that body mass index (BMI) remains a reliable indicator of excess body fat in most adults, contrary to growing concerns about its accuracy. Researchers from Johns Hopkins University analyzed data from over 2,200 US adults aged 20-59 and found that nearly all those identified as having obesity based on BMI also had confirmed excess adiposity.
The study used standardized measurements such as height, weight, waist circumference, and dual-energy X-ray absorptiometry (DEXA) to determine body fat percentages. Participants were considered to have confirmed excess adiposity if they met specific criteria for elevated BMI, waist circumference, or body fat percentage, or had a BMI of 40 or greater.
When only considering BMI, the study found that 39.7% of adults met the definition of obesity. However, when using BMI in conjunction with these confirmation criteria, the prevalence dropped slightly to 39.1%. Notably, 98.4% of persons with obesity based on BMI had confirmed excess adiposity.
The researchers suggest that while certain groups, such as athletes, may require individualized assessment, this likely represents a small portion of the population. For most US adults with elevated BMI, there may be limited need to confirm excess adiposity due to technical and cost challenges associated with body fat confirmation in clinical settings.
Overall, the study provides reassuring evidence for the reliability of BMI as an indicator of excess adiposity, suggesting that confirmatory tests may be unnecessary for most cases.
Source: https://medicalxpress.com/news/2025-04-bmi-reliable-indicator-excess-body.html