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Estimating weight on a standard scale does not always give an accurate measurement of body 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. This method, also called underwater weighing, involves being weighed underwater. 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 forgo this test.
Before the person is weighed under water, he is usually weighed on land. Measurements of lung volume should also be taken so that accurate calculations can be made during the test. Mistakes in these measurements can lead to inaccurate test results.
Those undergoing hydrostatic weighing generally sit in a chair, attached to a scale, in warm water that is slightly under their chin. The person is then asked to exhale as much air as possible and to completely submerge his or her head into the water for a few seconds. The process from start to finish takes about 20 to 30 minutes, and includes instructions prior to the weighing as well as outfitting the person being weighed.
After deducting the residual air in the lungs, the result is the subjects weight under water. This is entered into a calculation which also takes into account the weight taken on land and other factors to determine body density. This figure can then be used to determine the person's body fat percentage.
Those who try hydrostatic weighing are often surprised, either pleasantly or negatively, by the results. Trained athletes often have higher than average standard weight than non-athletes, but they often have quite low body fat counts. Muscle weighs more than fat.
Conversely, sometimes thin people have a higher than normal fat percentage. These people are generally surprised if 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 raises lean muscle mass.
Some health clubs and dieting organizations offer hydrostatic weighing. There are also clinics specifically for hydrostatic weighing and nutritional advice. Not many doctors offer this technology, although they may refer a patient to a specialist or clinic offering the test. Often, treatment centers for anorexia and other eating disorders 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 thus body fat. It is, however, expensive, and infrequently covered by health insurance. Should one be unable to afford this type of weighing, one can ask doctors about the noninvasive and quick skin fold test. Most doctors can perform this upon a patient’s request.