Body Mass Index vs Body Fat Percentage as a Predictor of Mortality in Adults Aged 20-49 Years.
Level 3 - non-randomized controlled study
Prospective observational cohort follow-up study
PubMed 40555527 · doi:10.1370/afm.240330
What was done
In a prospective cohort of US adults aged 20–49 years from the National Health and Nutrition Examination Survey (NHANES), Cox proportional hazards regression was used to evaluate 15-year all-cause and heart disease mortality risk. Body mass index (BMI; healthy 18.5–24.9 vs overweight/obese ≥25 kg/m²), body fat percentage (BF%; unhealthy defined as ≥27% for men, ≥44% for women), and waist circumference (WC; unhealthy defined as >40 inches for men, >35 inches for women) were compared.
What was found
Unhealthy BF% significantly predicted 15-year all-cause mortality (unadjusted HR 2.01, 95% CI 1.45–2.78, P < .001; adjusted HR 1.78, 95% CI 1.28–2.47, P < .001) and heart disease mortality (unadjusted HR 4.20, 95% CI 1.94–9.11, P < .001; adjusted HR 3.62, 95% CI 1.55–8.45, P = .003). Unhealthy WC was also associated with all-cause mortality (adjusted HR 1.59, 95% CI 1.12–2.26, P = .009) and heart disease mortality (adjusted HR 4.01, 95% CI 1.94–8.27, P < .001). BMI had no statistically significant association with all-cause mortality and was not significantly associated with heart disease mortality after adjustment.
Why it matters
Body fat percentage and waist circumference provide superior mortality risk stratification compared to BMI in adults under 50.
Limits
The abstract does not state the sample size (n), specific NHANES cohorts included, or the specific covariates adjusted for. Observational cohort design susceptible to residual confounding.
Cited by
- supports Mortality data indicates that being extremely lean is associated with increased mortality risk, whereas maintaining approximately 15% to 20% body fat in males has a protective effect compared to 30% to 40% body fat.