Researchers Reveal Better Way to Measure Health Than BMI - Video

A new study from the University of Florida Health, published in the Annals of Family Medicine, challenges the long-standing use of body mass index (BMI) as a key indicator of health risk. The findings show that BMI is a poor predictor of long-term mortality, and suggest that a more direct measure of body fat bioelectrical impedance analysis offers a significantly better assessment of health risk.

BMI does not differentiate between muscle and fat, limiting its accuracy as an indicator of actual body composition. To assess its validity, researchers compared BMI with direct measurements of body fat.

The study analyzed data from 4,252 adults who participated in the National Health and Nutrition Examination Survey and were tracked for 15 years through the national death index. Researchers used bioelectrical impedance analysis, a method that gauges body fat by measuring the resistance of body tissues to a small electrical current a technology that is increasingly available in clinical settings.

The results were striking. Individuals with high body fat levels as measured by impedance analysis were 78% more likely to die of any cause, and about 3.5 times more likely to die from heart disease, compared to those with healthy body fat levels. BMI, by contrast, showed no statistically significant association with mortality from any cause.

Senior author Dr. Frank Orlando medical director of UF Health Family Medicine – Springhill, said BMI’s use as a “vital sign” of health isn’t supported by good evidence. “One of the routine measures we take alongside traditional vital signs is BMI. We use BMI to sort of screen for a person having an issue with their body composition, but it’s not accurate for everyone like vital signs are,” he added.

The authors call for a shift in clinical practice, urging the medical community to replace BMI with more accurate tools to evaluate body composition and health risk.

Reference: Body Mass Index vs Body Fat Percentage as a Predictor of Mortality in Adults Aged 20-49 Years

Arch G. Mainous, Lu Yin, Velyn Wu, Pooja Sharma, Breana M. Jenkins, Aaron A. Saguil, Danielle S. Nelson, Frank A. Orlando

The Annals of Family Medicine Jun 2025, 240330; DOI: 10.1370/afm.240330