The Best Way to Measure Body Fat

The best way to measure body fat is not always the easiest method, but there are a number of different things you can do to find out where you are in terms of body composition.

Why Measure?

First, we must understand why on earth we would pinch, plunge and electrode ourselves to find body fat. When starting a weight loss plan, it is a good idea to know your body composition before starting. Knowing your body composition is a useful weight loss tool to determine the kinds of exercises you need to be doing. For example, if you have a low amount of body fat, you might be working out to build muscle, and because of this, you’re going to need to make sure you supplement the amount of calories you burn to stay at a healthy weight. The same goes for a high amount of body fat; work hard to burn more and get in a healthy range. 

What Is the Best Way to Measure?

The “golden” standard for measuring body fat is currently the hydrodensitometry method, known as hydrostatic or under-water weighing. The body is divided into two components: fat, and fat-free, and then weighed under specific conditions under water. Weighing the body under water provides an estimate of body volume from the water displaced by the body’s volume. Hydrostatic weighing involves totally submerging the body in a special tank. The subject sits on a scale and blows as much air out of the lungs as possible, then the weight is measured. The body volume is corrected for the residual air in the lungs as well as air in the intestinal tract. After the measurement is taken, the mass is used in the following equation to estimate volume:

  • body volume=[(body mass-net underwater weight)/density of water]-(residual volume+gastrointestinal volume)

When the body volume is acquired, it is used to find body density (Db) by dividing the body mass in kg by the body volume in liters. The Db is then plugged in to a population and sex-specific equation to find the percent body fat. For example, the equation for a female age 18-59 is: %BF=(4.96/Db)-4.51. The hydrostatic method is widely used because of it’s accuracy and reliability, but this method can be scary for some.

Are There Other Methods?

There are absolutely other methods. Realistically, not everyone has a hydrostatic tank in their backyard, nor does everyone care to get in a swimsuit, blow out all the air they can and get dunked. Because of the somewhat invasive nature of the hydrostatic method, sometimes other methods can be used. A good alternative is the air displacement plethysmography method, which is a fancy way of saying that it’s just about the same as hydrostatic, but with air instead. The subject gets into an air-tight chamber and body volume is estimated using air displacement. It’s nice and dry, but not always pleasant for someone who doesn’t like tight spaces.

Another method is to measure skinfolds. In this method, the skin is lightly pinched, pulled out, and measured with skinfold calipers. This method is inexpensive, and when done correctly, it is relatively accurate. Bioelectrical Impedance is yet another method that is comfortable and takes little or no effort. The subject lays flat and a low-level electrical current is passed through the subject’s body. The impedance, or opposition to the flow of electricity is them measured with the BIA analyzer. Although it might sound scary, the electrical current is so low, the subject can’t even feel it.

For easy to use, at home methods, you can use a body mass index (BMI) calculation or height and weight tables. The equation to find you BMI is:

  • BMI= (weight in kg)/(height in cm x height in cm)

This results of this equation give you a number that you can compare to a chart to see how you compare to others of you race and gender. You can also use a height and weight table to assess your body. By lining up your height and weight and drawing a straight line on the table, you can find what your ideal weight should be. Both the BMI equation and the height and weight table are very limited because they don’t tell you your actual body composition, so be careful when you use them.

Taking the hydrostatic weight of an individual is the best way to measure body fat. It is not always easy or convenient, but it gives the best results and is the most reliable method.

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