For decades, body mass index (BMI) has been the go-to tool for assessing weight-related health risks.
But a new study published in The Annals of Family Medicine suggests it may be time to rethink that approach.
Researchers from the University of Florida analyzed data from 4,252 adults between 20 and 49 years old who participated in the National Health and Nutrition Examination Survey (NHANES). They compared BMI, body fat percentage and waist size with deaths from all causes and heart disease over 15 years.
The results were striking: Body fat percentage and waist size were much stronger predictors of death than BMI. Adults with a high body fat percentage, 27% or more for men and 44% or more for women, were 1.78 times more likely to die from any cause and 3.62 times more likely to die from heart disease than those in a healthier range. Waist size told a similar story, while BMI showed no significant association with mortality after adjustments.
“Body fat percentage had a much stronger association with 15-year mortality than the standard body composition measure of BMI,” the researchers wrote.
Unlike BMI, which only compares weight and height, body fat percentage reflects how your eating patterns and lifestyle shape your body composition. It can uncover “normal-weight obesity,” when someone has a “healthy” BMI but still carries too much body fat, which can raise the risk for heart disease and metabolic problems.
The good news? Body fat percentage is easier to measure than ever. Devices that use bioelectrical impedance (often built into modern scales) provide quick, noninvasive readings and are becoming more affordable. That means you can track not just your weight but how your food choices are affecting your health over time.
For anyone working on weight loss, improving heart health or simply wanting to better understand how their diet is working for them, tracking body fat percentage could be a game-changer.
This study used publicly available data from the National Health and Nutrition Examination Survey (NHANES) linked to the National Death Index. The authors reported no external funding.