New Study Confirms BMI as a Reliable Measure of Excess Body Fat in Most Adults

Recent research conducted by Johns Hopkins University has strengthened the evidence supporting body mass index (BMI) as a dependable indicator of excess body fat in the adult population. The study examined data from over 2,200 adults aged 20 to 59 participating in the 2017–2018 National Health and Nutrition Examination Survey (NHANES), utilizing measurements such as height, weight, waist circumference, and dual-energy X-ray absorptiometry (DEXA) scans to accurately assess body fat levels.

The findings revealed that nearly all adults classified as obese based on BMI also exhibited confirmed excess adiposity, a condition characterized by abnormally high body fat. Specifically, when BMI was used as the sole criterion, approximately 39.7% of participants were categorized as obese. Upon applying additional measures to confirm excess body fat—such as waist circumference or DEXA scans—the prevalence slightly decreased to 39.1%. Notably, an overwhelming 98.4% of individuals with a BMI indicating obesity also had confirmed excess adiposity.

The study highlighted that the correlation between BMI and actual body fat levels was consistent across different ages, sexes, and racial or ethnic groups. This suggests that, despite some controversies, BMI remains a practical and reliable tool for identifying excess body fat in most adults. The research also indicates that in clinical settings where advanced assessments like DEXA are costly and complex, BMI alone can often suffice for obesity screening, except potentially for small groups such as athletes, who may require more personalized evaluation.

While BMI does not distinguish between muscle and bone mass, the near-perfect correlation with confirmed excess adiposity in this large population-based study underscores its ongoing utility as a screening measure. These insights can help streamline obesity diagnosis and management, ultimately improving public health strategies against obesity-related health risks.

For further details, this research is published in the Journal of the American Medical Association (JAMA). More information can be found here.