Why Body Fat Percentage is Better Than BMI

For decades, doctors have relied on the Body Mass Index (BMI) to screen patients for weight-related health risks. However, BMI is inherently flawed because it simply divides total weight by height. It cannot tell the difference between a 200-pound man carrying 60 pounds of dangerous visceral fat, and a 200-pound professional athlete carrying 180 pounds of healthy muscle.

Body Fat Percentage is a far superior metric because it isolates exactly how much of your mass is adipose tissue (fat). By tracking your body fat percentage, you ensure that any weight you lose is actually fat, rather than precious muscle mass or water.

The U.S. Navy Tape Measure Method

There are many ways to measure body fat. DEXA scans are highly accurate but cost hundreds of dollars. Calipers are cheap but require a trained professional to pinch your skinfolds accurately. Bioelectrical impedance scales (smart scales) are notoriously inaccurate because they are skewed by how much water you drank that day.

The U.S. Navy Method was developed to quickly and accurately screen thousands of military recruits. By measuring the circumferences of the body where fat naturally accumulates (the waist and hips) and subtracting the circumference of an area where fat rarely accumulates (the neck), the formula can triangulate your body density. Clinical studies have shown this tape measure method is incredibly accurate, usually falling within 3-4% of expensive DEXA scans.

Understanding Lean Body Mass (LBM)

This calculator also provides your Lean Body Mass. This is arguably the most important number for longevity. LBM is the weight of your skeleton, your organs, and your skeletal muscle.

As we age, we naturally lose muscle mass (Sarcopenia) and bone density. If you attempt to lose weight by simply starving yourself, a large portion of the weight lost will be from your Lean Body Mass. This suppresses your metabolism and makes you frail. A healthy diet combined with resistance training (weightlifting) ensures that you preserve your Lean Body Mass while forcing your body to burn its fat reserves.