Relative Fat Mass (RFM)
Relative fat mass (RFM) is a simple formula using your height and waist size that estimates body fat percentage without any special equipment.
Plain English
Patient-Friendly Explanation
Relative fat mass, or RFM, is a way of estimating how much of your body is fat using just two measurements: your height and your waist circumference. It was developed by researchers who compared thousands of body scans and found that waist size relative to height predicts total body fat very well — better than BMI alone in several studies. RFM is calculated with a straightforward formula and needs no scanner, so you or your doctor can work it out in any clinic. It is especially useful for spotting people who have a normal BMI but carry excess fat, a pattern linked to the same metabolic risks as visible obesity.
Medical
Clinical Definition
RFM, introduced by Woolcott and Bergman (2018), estimates whole-body fat percentage from height and waist circumference using sex-specific equations: for men, RFM = 64 − 20 × (height/waist); for women, RFM = 76 − 20 × (height/waist), with both measurements in the same units. In the original NHANES derivation and subsequent external validations against dual-energy X-ray absorptiometry, RFM performed comparably to or better than BMI at classifying excess adiposity, with particular value in detecting normal-weight obesity. Waist measurement technique must be consistent (midpoint between the lowest rib and iliac crest, at end-expiration), and population differences mean Asian-specific body-fat thresholds and clinical judgement still apply. RFM is a practical, equipment-free screening index — not a substitute for DEXA or BIA when precise body-composition quantification changes management.
Key Insight
Why It Matters
Two patients can share a BMI yet have very different amounts of body fat. When we want a fast, free estimate of whether body fat is driving your metabolic risk, we can calculate RFM from measurements taken in the consultation — and use DEXA or BIA whenever a precise breakdown is needed.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: September 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
