The most familiar method of measuring ideal weight is the height and weight chart. These tables, guide you how much you should weigh based on your height. Although these tables are still popular, they are very ambiguous, especially to sportsperson and bodybuilders who carry more muscle than most people do. â€Ideal weights†from height-weight tables do not take body fat into account; therefore, they cannot accurately recommend how much you should weigh. Body Mass Index (BMI) is another familiar way to determine whether someone is at a â€healthy weightâ€. Like the height and weight tables, BMI is a valueless measure of fitness because it takes only height and weight into account. In addition, it does not take into account fat versus muscle tissue. Body builders and other sportsperson carry more lean body mass than the average person and will therefore be classified as overweight if BMI is used as the criteria for measurement. The primary objective to measure percentage body fat is so you can tell between fat and muscle, which the ideal weight and BMI calculator does not. Average percentage body fat vary among the sexes and among different age groups. The female hormone estrogen causes women to carry about 5% more body fat than men. The average woman has about 23% body fat and the average man approximately 17%. In both sexes, body fat increases with age while lean body mass decreases. The following are the techniques widely used for determination of percentage body fat. Underwater Weighing (Hydrostatic) Underwater Weighing has always been considered the best for measuring the percentage body fat in comparison with other measurement techniques. The basis for hydrostatic weighing is the fact that fat floats and muscle sinks. To get your fat measured by underwater weighing, the person must remain dunked underwater in a chair that hangs from a scale. The more fat you are, the more buoyant you will be, and the more buoyant you are, the less you will weigh underwater. However, underweight weighing has its own drawbacks; the major one is the difficulty of being dunked in water. Notwithstanding, this method underestimates the fat percentage for persons with denser bones. Unless race, age, and sex are carefully taken into account, the estimate of body fat could be having a significant error. To summarize, underwater weighing is not very practical, though it is always interesting to go get it done once in a while just for fun. Bio- Electric Impedance Analysis Bioelectric Impedance Analysis (BIA) is a modern scientific instrument that measures percentage body fat by testing the electrical conductivity of your body’s cells to a flow a small harmless electrical signal. Fat has a low water content in comparison with muscle, so has an insulating effect, and is therefore less conductive. Research have shown that BIA is a fairly accurate and valid measure of percentage body fat. The impedance measure is affected by body hydration status, body temperature, time of day, and therefore requires identical conditions to get accurate and reliable measurements. If a person is dehydrated, the amount of fat will likely be overestimated. Near Infrared Interactance Near Infrared Interactance (NIR) is based on light absorption and reflection to determine percentage body fat. The measurement is taken on the person’s dominant arm. The light wand sends a beam of infrared light into the body where shifts in the reflections of the wavelengths are used to estimate total body fat percentage. The measurement is very safe, simple and easy to use with less practice. The drawbacks include the high cost of the instrument, and the questionable accuracy and reliability like relating fat in arm to body fat percentage, which may not be true. Skinfold Measurement Skinfold testing is based on the fact that most of the body fat is stored directly beneath your skin. The skinfold test is performed with a simple machine called a skinfold caliper. The jaws of the caliper pinch a fold of skin and fat and measure the thickness of the fat fold in millimeters. Using the calipers, skinfolds measurements are taken at different sites around the body and then the measurements are added up. The sum of the skinfolds is then looked up on a body fat estimate chart that is available with the calipers. A skilled tester can produce a body fat measurement with accuracy very close to underwater weighing, which is considered to be standard of body composition testing. Most importantly, skinfold testing is extremely practical and lot more simpler than many of the measurement techniques. However, the accuracy of the measurements may vary from tester to tester. Other Methods There are many other methods used to determine percentage body fat, including Total Body Potassium, Dual-Energy X-Ray Absorptiometry (DEXA), Total Body Electrical Conductivity (TOBEC), Whole-Body Air-Displacement Plethysmography, Magnetic Resonance Imaging (MRI) and Computed Tomography (CT scan). While some of these sophisticated methods may be incredibly reliable and useful in the laboratory, none of these methods is practical at least for personal use for a weight loss program. Now you understand the importance of body fat versus body weight and you understand that height and weight and Body Mass Index (BMI) tables are worthless. It is also clear that losing weight is not of prime importance, but losing fat is.
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