Weight estimation on a standard scale does not always provide an accurate measure of the body's health. Since a high percentage of body fat can significantly affect health, hydrostatic weighing can be used to measure not in pounds but in body density. Hydrostatic weighing, also called underwater weighing , implies being heavy under water. It is not a particularly complex form of weighing, but it does require one to be completely submerged in water for a few seconds. Those who have a significant fear of being completely underwater should probably forego this test.
Before a person is weighed underwater, they are usually weighed on land. Lung volume measurements should also be taken so that accurate calculations can be made during the test. Errors in these measurements can lead to inaccurate test results.
Those undergoing hydrostatic weighing typically sit on a chair, attached to a scale, in warm water that is slightly below the chin. The person is then asked to exhale as much air as possible and completely submerge their head in the water for a few seconds. The process from start to finish takes between 20 and 30 minutes and includes instructions before the hydrostatic weigh-in, as well as the equipment of the person being weighed.
After deducting residual air in the lungs, the result is the weight of the subject underwater. This is entered into a calculation that also takes into account weight taken on land and other factors to determine body density. This number can be used to determine the person's body fat percentage.
Those who try hydrostatic weighing are often pleasantly or negatively surprised by the results. Trained athletes often have a higher than average standard weight than non-athletes, but when hydrostatic weighed, they often have fairly low body fat counts. Muscle weighs more than fat.
Conversely, thin people sometimes have a higher than normal fat percentage. These people are usually surprised if the body density does not fall within a normal range. This information can be helpful in planning a healthy diet and exercise regimen that reduces body fat content and increases lean muscle mass.
Some health clubs and diet organizations offer hydrostatic weighing. There are also specific clinics for hydrostatic weighing and nutritional advice. Not many doctors offer this technology, although they may refer a patient to a specialist or clinic that offers the test. Treatment centers for anorexia and other eating disorders often have hydrostatic weighing equipment, as it can help focus patients on weight not derived from a scale and may cause less concern for patients who need to be weighed .
Hydrostatic weighing is currently considered the best method for measuring body density and therefore body fat. However, it is expensive and is rarely covered by health insurance. If one cannot afford this type of weighing, one can ask the doctors about the non-invasive and rapid skinfold test. Most doctors can do this at the request of the patient.