Hydrostatic body fat test
The Hydrostatic body fat test is one of the most accurate. There are various methods available to determine how much fat or mass your body contain. There are very few methods those can provide more precise results about the body composition that is body fat to lean mass. Body fat by age, body fat by gender, dexa body fat, calipers, NIR, MRI, TOBEC, CT, BOD POD, BIA, and many more. There is one more method to test the body composition i.e. body fat to lean mass. The Hydrostatic body fat test is the method that measures the whole body density through determining the body volume. This is underwater weighing way to measure the mass density of the body.
Different equipment is used for underwater weighing. There are standard stainless steel tank with chair or cot mounted on underwater scales. The scale suspended from diving board over a hot tub or pool. The procedure is based on the Archimedes principle. In this body fat test three measurable values are taken such as the weight of the body outside the water, the weight of immersed body and density of the water. The formula states that result of density of body divided by the density of water is same as the weight of body divided by weight of body less weight of immersed body.
To determine the fat or body mass, first the person is weighed outside the tank. Then immersing him or her totally in the water and weighing him or her again. The person with more bone and more muscles weigh more in the water and lower percentage of fat. The reason behind this is densities of muscles and bones are higher in the water and the fat is less dense than the water. In a hydrostatic body fat test the volume of the body is calculated and the density of the individual’s body is determined by using above mentioned formula. The body fat percentage is measured or calculated from the body density using the standard equations.
Under water weighing may not be perfect gold standard for every person. This happens with athletes and non-athletes. The athletes have denser muscles and bones as compared to non-athletes. The body fat of elder patients might be overestimated. This body fat test has standard formula to determine body mass. However, no specific equations are developed yet to accommodate with different population groups. The results produced by this method are precise to the extent of some precautions. It is impossible to have completely still water with no wind and movement. The residual volume in the lungs adds error if not measured directly.
Although the hydrostatic body fat test method is considered as laboratory ‘gold standard’ most of the person find it difficult, uncomfortable, and cumbersome. From this method density information about body composition that is body fat to lean fat and percentage of body fat may be determined. This method is used for assessment of obesity. Hydrostatic body fat testing provides percent body fat and body density with the help of two formulas namely Siri and Brozek. This procedure is based on Archimedes principle.