Fat-Free Mass Index (FFMI)
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The formula for FFMI is: Lean Mass (kg) / Height (m)²
Normalized FFMI = FFMI + (6.1 × (1.8 - Height in meters))
Why BMI is Flawed for Longevity
Body Mass Index (BMI) does not distinguish between fat mass and muscle mass. In the context of longevity, maintaining lean body mass is critical to prevent sarcopenia and frailty in older age.
FFMI measures the amount of muscle mass relative to height. An average male score is around 19, while a natural bodybuilder might reach 23-25. Tracking FFMI over decades ensures that age-related weight loss is not secretly masking muscle atrophy.