Muscle mass index below key thresholds signals real health risk

Full analysis

Andy Galpin explains that muscle mass has a floor below which health deteriorates regardless of how you look. The metric to watch is FFMI — Fat Free Mass Index — a calculation that adjusts for height and factors out body fat, giving a true picture of how much lean muscle you carry. An FFMI of 20 or higher is the target for men; 18 or higher for women. Below 17 (men) or 15 (women), Galpin says you are in a zone of "pretty severe physiological detriment." You can calculate FFMI using free online calculators that only need your total body weight, body fat percentage, and height; a DEXA scan (a low-radiation imaging test that measures bone density and body composition) is the gold standard for accuracy, though simpler bioelectrical impedance devices give reasonable estimates.