Which method measures body fat percentage by submerging the body in water?

• A. Skin calipers
• B. Bioelectrical impedance monitors
• C. Hydrostatic weighing
• D. 3D body scan

Answer: (C)

Hydrostatic weighing measures body fat percentage by submerging the body in water to determine body density. By weighing a person on land and then underwater (usually after exhaling to reduce lung volume), the difference reveals body volume through buoyancy. With body density known, a conversion equation (such as Siri) estimates fat percentage. The reason this method works is that fat tissue is less dense than lean tissue, so a higher fat percentage lowers overall density, which can be translated into fat percentage from density. Other methods—skinfold measurements gauge subcutaneous fat with calipers, bioelectrical impedance uses body water and resistance, and 3D scans estimate volume from imaging—do not involve water immersion.