Body composition refers to the proportions of fat, muscle, bone, and water in your body. Unlike BMI, which only considers weight and height, body composition distinguishes between fat mass and lean mass, providing a much more meaningful picture of health and fitness.

Two people at the same weight and height can have vastly different health profiles. Someone with 15% body fat and significant muscle mass is metabolically healthier than someone with 30% body fat at the same weight. Composition, not just weight, determines health risk.

Test every 4-8 weeks to track meaningful changes. More frequent testing introduces noise from hydration, food intake, and measurement variability. Always measure under consistent conditions — same time of day, hydration level, and measuring technique.