What's your FFMI?
Fat-Free Mass Index — muscle vs. natural limit
Medical Disclaimer: This tool provides general educational estimates. Always consult your prescribing physician or healthcare provider before making medication changes or interpreting results from population-based models.
Frequently Asked Questions
Fat-Free Mass Index measures lean body mass relative to height: FFMI = lean mass (kg) / height (m)². It's like BMI but for muscle. The normalized version adjusts to a standard height of 1.80m.
The Kouri et al. (1995) study found that natural male athletes rarely exceed an FFMI of 25. For women, the estimated natural limit is approximately 21. Values above these thresholds suggest possible steroid use.
Methods include DEXA scans (most accurate), calipers, bioelectrical impedance scales, or visual estimation. Accuracy varies by method.
Sources
- Kouri EM, et al. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med. 1995;5(4):223-228. Link
Methodology
FFMI = lean mass (kg) / height (m)², where lean mass = weight × (1 - body fat / 100). Normalized FFMI adjusts for height: FFMI + 6.1 × (1.80 - height in meters). Classification tiers are based on the Kouri et al. study of steroid users vs non-users.
Fat-Free Mass Index (FFMI) measures lean mass relative to height. FFMI = lean mass (kg) / height (m)². For men: below 18 is below average, 20-22 above average, 22-25 excellent to superior, above 25 exceeds the natural limit (Kouri et al., 1995). For women, subtract approximately 4-5 points. Normalized FFMI adjusts to 1.80m height.
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