Dual-energy X-ray absorptiometry (DEXA) is the most accurate and advanced test available for measuring bone density. The DEXA is also being used to measure body fat. Because the DEXA can distinguish between fat, bone, and muscle (a three-compartment model), it provides a more precise measure of body fat than methods such as underwater weighing and skinfold techniques. Underwater weighing provides an estimate of fat weight and nonfat weight (a two-compartment model), while skinfold techniques make assumptions about the uniform distribution of fat throughout the body. Skinfold measures, when done correctly, can provide accurate predictions of body fat. Skinfold techniques are still more popular than the DEXA because they are easier to perform and the equipment is significantly less expensive.
