High Body Fat, Not BMI, Linked to Increased Risk of Death and Heart Disease: Study Finds - Video

A new study published in the Annals of Internal Medicine suggests that body fat percentage may be a far more accurate predictor of long-term health outcomes than the widely used body mass index (BMI). The research highlights the shortcomings of relying solely on BMI and supports a shift toward more precise body composition measurements in clinical practice.

Although BMI is a convenient tool for categorizing individuals based on weight relative to height, it does not distinguish between fat and lean mass. As a result, it may misclassify muscular individuals as overweight and overlook those with “normal-weight obesity,” people who have a normal BMI but high body fat, which can still carry serious health risks.

In this study, researchers from the University of Florida analyzed data from 4,252 adults aged 20 to 49 who participated in the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2004. All participants had complete technician-measured body composition data, including height, weight, and waist circumference, and their records were linked to the National Death Index through 2019. Body fat percentage was assessed using bioelectrical impedance analysis, a non-invasive method now becoming more feasible in clinical settings.

The results were striking: Adults with high body fat (defined as ≥27% in men and ≥44% in women) were 1.78 times more likely to die from any cause and 3.62 times more likely to die from heart disease compared to those with a healthy fat percentage. In contrast, individuals with a BMI in the overweight or obese range (≥25 kg/m²) did not show a significantly increased risk of death from any cause.

Additionally, a high waist circumference (over 40 inches in men and 35 inches in women) was associated with a 1.59-fold increased risk of all-cause mortality and a 4.01-fold higher risk of death from heart disease.

These findings support a reevaluation of how body composition is assessed in clinical care. “New bioelectrical impedance devices could make it feasible to move beyond BMI in routine health assessments,” the researchers noted. As obesity-related illnesses continue to rise, accurate screening tools could help identify at-risk individuals earlier and guide better preventive strategies.

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 Jul 2025, 23 (4) 337-343; DOI: 10.1370/afm.240330