Clinical Medicine & Physiology
Relative Fat Mass (RFM) Calculator: Woolcott & Bergman Height-to-Waist DXA Formula
Estimate whole-body fat percentage without a weight scale using Orison O. Woolcott and Richard N. Bergman’s (2018) NHANES DXA-validated Relative Fat Mass equation RFM = 64 - 20 * (Height / Waist) + 12 * Sex_Female(0/1).
Estimate DXA whole-body fat percentage from a tape measure alone — NO bathroom scale required!
Body Mass Index (BMI = Weight / Height^2) cannot distinguish skeletal muscle hypertrophy from central adiposity! Screening 365 anthropometric ratios against Dual-Energy X-ray Absorptiometry (DXA) whole-body fat percentage across >12,000 US adults in NHANES 1999–2006, Orison O. Woolcott and Richard N. Bergman (2018, Scientific Reports, Cedars-Sinai) discovered a remarkably accurate linear law requiring ONLY Height and Waist Circumference (measured at the iliac crest in identical units, cm or inches):
RFM (%) = 64 - 20 * (Height / Waist) + (12 * Sex_Female_0_1) — i.e., 64 - 20 * (H / W) in adult men and 76 - 20 * (H / W) in adult women! Validated subsequently for obesity-related mortality and cardiometabolic risk (Woolcott & Bergman, 2020, Int. J. Obes.), high-adiposity cutoffs are >= 30.0% in adult men and >= 40.0% in adult women!
| Adult Subject (Same Units for Height & Waist) | Height / Waist Ratio | Woolcott-Bergman RFM (%) | Obesity Cutoff Comparison |
|---|---|---|---|
| Adult Male (Height = 178 cm, Waist = 86 cm) | 2.0698 | 22.60% BF | Below >= 30.0% male cutoff |
| Adult Male (Height = 178 cm, Waist = 106 cm) | 1.6792 | 30.42% BF | Exceeds >= 30.0% male cutoff |
| Adult Female (Height = 165 cm, Waist = 88 cm) | 1.8750 | 38.50% BF | Below >= 40.0% female cutoff |
Woolcott-Bergman (2018) Adult Relative Fat Mass RFM (%)
Evaluates 64 - 20 * (Height_cm / Waist_cm) + 12 * Female_0_1 across Height B2 (120–230 cm), Waist B3 (45–200 cm), and Sex B4 ("M" or "F").
=IF(OR(B2 < 120, B2 > 230, B3 < 45, B3 > 200, AND(B4 <> "M", B4 <> "F")), "Invalid Adult Height, Waist, or Sex (M/F)", ROUND(64 - 20 * (B2 / B3) + IF(B4 = "F", 12, 0), 2))Sex-Specific RFM Obesity Threshold Classification (>= 30% M / >= 40% F)
Compares computed RFM against Woolcott & Bergman’s (2020) mortality-linked adiposity cutoffs (>= 30% in men, >= 40% in women).
=IF(OR(B2 < 120, B2 > 230, B3 < 45, B3 > 200, AND(B4 <> "M", B4 <> "F")), "Invalid Adult Height, Waist, or Sex (M/F)", IF((64 - 20 * (B2 / B3) + IF(B4 = "F", 12, 0)) >= IF(B4 = "F", 40, 30), "Elevated RFM Adiposity (>= Sex-Specific Cutoff)", "RFM Below High-Risk Adiposity Cutoff"))Try the example
Use the original values or change them to test your understanding.