Body Composition

• $65 for skinfolds, hydrostatic weighing, and BOD POD
• $30 for BOD POD and skinfolds
• $35 for hydrostatic weighing and skinfolds
• Pretest Instructions (pdf)

Body composition refers to the percentages of body weight that are comprised of fat and lean tissue. Percent body fat is important for health-related fitness because individuals who have an excess amount of body fat are at greater risk of developing chronic diseases including cancer, coronary artery disease, hypertension, non-insulin-dependent diabetes and osteoarthritis. Body composition is more useful and descriptive than body mass index (BMI) because it discerns between fat and non-fat tissue in the body.

The recommended level of percent body fat varies according to age and sex. In general, a percent body fat greater than 25% for men and greater than 30% for women is considered "overfat". Recommended levels of percent body fat are higher for women than for men because women naturally have a higher amount of "essential" body fat, which is a function of their reproductive physiology.

Skinfolds

Body composition will be determined by measuring skinfold thickness at three sites: 1) chest 2) abdomen 3) thigh (males) OR 1) triceps 2) iliac crest 3) thigh (females). The sum of the three skinfold measurements can be used to provide an estimate of percent body fat, i.e., the percentage of body weight that is comprised of fat tissue.

Hydrostatic Weighing

Hydrostatic (underwater) weighing is generally regarded as the "gold standard" for body composition assessment. Because body fat is less dense than water, it increases one's buoyancy. Fat-free mass is denser than water and causes one to sink. After correcting for residual volume, body density can be calculated based on the underwater weight. Using body density, percent fat can then be estimated.

BOD POD

The BOD POD is based on the same principle as underwater weighing. Rather than displacing water, the individual will displace air, which can be detected via pressure changes in the chamber. The BOD POD uses a patented air displacement technology to provide highly accurate results more quickly and easily than underwater weighing.