What is Body Fat Percentage?
Body fat percentage is the proportion of fat relative to total weight. Unlike BMI, distinguishes fat mass from lean mass (muscles, bones, organs). Methods include DEXA (gold standard), bioimpedance and circumferences (U.S. Navy). This uses waist, neck, hip and height measurements to estimate % fat.
U.S. Navy formula uses logarithms of circumferences and height
How to Calculate?
U.S. Navy method was developed for military personnel. Men: measures waist, neck and height. Women: adds hip. Uses logarithmic formulas validated against reference methods. Accuracy: ±3-4%. For best results: measure in the morning, waist at navel, neck below Adam's apple, hip at widest part.
Frequently Asked Questions
What % fat is healthy?
Men: essential 2-5%, athlete 6-13%, fitness 14-17%, average 18-24%, >25% obesity. Women: essential 10-13%, athlete 14-20%, fitness 21-24%, average 25-31%, >32% obesity. Athletes tend to have lower %. Too low can cause hormonal, immune and bone issues, especially in women.
Is Navy method accurate?
Moderate accuracy (±3-4%). Better than BMI by considering body composition, but inferior to DEXA (±1-2%) or hydrostatic weighing. Advantages: cheap, non-invasive, reproducible. Limitations: may underestimate in muscular athletes or overestimate in people with atypical fat distribution. Use to track changes over time.
How to measure circumferences correctly?
Use flexible but non-elastic measuring tape. Waist: at navel, at end of normal expiration, without sucking in stomach. Neck: below Adam's apple (men) or at thinnest part (women), perpendicular to axis. Hip (women): at widest part of buttocks. Repeat 2-3 times, use average.
How to reduce % fat?
Caloric deficit combined with exercise: 1) Nutrition: 300-500 kcal/day deficit, adequate protein (1.6-2.2g/kg) to preserve muscle; 2) Strength training: maintains/increases lean mass; 3) Moderate cardio: increases caloric expenditure; 4) Sleep and recovery. Healthy loss: 0.5-1% body fat/month. Avoid extreme diets.
What's the difference between % fat and BMI?
BMI: weight/height² - doesn't distinguish fat from muscle. Muscular athletes may have high BMI but low % fat. Sedentary people may have normal BMI but high % fat (sarcopenic obesity). % fat is better indicator of metabolic health and cardiovascular risk. Use both complementarily.