How to Measure Body Fat Percentage

Published: 05th January 2009
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The most popular method of determining ideal weight is the height and weight chart. These charts, tell you how much you should weigh based on your height. Although these charts are still popular, they are very inaccurate, specially to athletes and bodybuilders who carry more muscle than most people do. "Ideal weights" from height-weight charts do not take body fat into consideration; therefore, they cannot accurately recommend how much you should weigh.



Body Mass Index (BMI) is another popular way to determine whether someone is at a "healthy weight". Like the height and weight charts, BMI is a valueless measure of fitness because it takes only height and weight into consideration. In addition, it does not take into account fat versus muscle tissue. Body builders and other athletes carry more lean body mass than the average person and will therefore be classified as overweight if BMI is used as the criteria for determination.



The significance in measuring body composition 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 body composition.



Underwater Weighing (Hydrostatic)

Underwater Weighing has constantly been considered the best for measuring the body composition in comparison with other measurement techniques. The basis for hydrostatic weighing is the fact that fat floats and muscle sinks. To measure your fat by underwater weighing, the person should remain motionless underwater in a chair that hangs from a scale. The fatter you are, the more buoyant you will be, and the more buoyant you are, the less you will weigh underwater. Neverthless, underweight weighing has its own drawbacks; the major one is the difficulty of being motionless in water. Notwithstanding, this method underestimates the fat percentage for persons with denser bones. Unless race, age, and sex are all carefully taken into consideration, the estimate of body fat could be having a serious error. To summarize, underwater weighing is not very practicable, although 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 which determines body composition by testing the electrical conductivity of your body's cells to a flow a small harmless current. Fat has a low water content compared to muscle, so has an insulating effect, and is therefore less conductive. Research shows that BIA is a fairly accurate and valid measure of body composition. The impedance measure is affected by body hydration status, body temperature, time of day, and therefore requires well controlled 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) uses the principle of light absorption and reflection to measure body composition. The measurement is taken on the person's dominant arm. The light wand sends a beam of infrared light into the body where variations 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 you store most of your body fat directly below your skin. The skinfold test is performed with a simple instrument 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 fat percentage estimate table that is available with the calipers. A competent tester can produce a body fat measurement with accuracy very close to benchmark standards. Most importantly, skinfold testing is extremely practicable and lot more simpler than many of the measurement techniques. However, the reliability of the measurements may vary from tester to tester.



Other Methods

There are many other techniques used to measure body composition, 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 came to know the importance of body fat versus body weight and you understand that height and weight and Body Mass Index (BMI) charts are worthless. It is also clear that losing weight is not of prime importance, but losing fat is.

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