Updated September 11, 2015.

When it comes to tracking weight loss, most of us rely on the scale to tell us whether we've lost or gained weight. But, as people are fast learning, this isn't the best way to keep track of your weight. A scale measures everything including muscle, fat, bones, and what you ate or drank that day. It doesn't tell you what you really need to know: how much fat do you have?
Body Composition

Body composition is simply the ratio of lean body mass to fat body mass.


Too much fat can lead to health problems like heart disease, diabetes, high cholesterol and other serious conditions. If you keep your body fat within a reasonable level, you'll be healthier and, of course, slimmer.

Body Fat Categories for Women

• 10-12% - Essential Fat
• 14-20% - Athletic Fat Levels
• 21-24% - Fitness Fat Levels
• 25-31% - Acceptable Fat Levels
• >32% - Obese

Body Fat Categories for Men

• 2-4% - Essential Fat
• 6-13% - Athletic Fat Levels
• 14-17% - Fitness Fat Levels
• 18-25% - Acceptable Fat levels
• >26% - Obese

So, how do you find out what your body fat is? Below are the most popular methods for testing body composition.

How to Test Your Body Fat

DEXA (dual energy X-ray absorptiometry)

This test is used to measure bone density, but it also measures body fat percentage as well as where most of your fat is (as if you didn't know). The facts about DEXA:

• DEXA uses a whole body scanner and two different low-dose x-rays to read bone mass and soft tissue mass.
• It takes about 10-20 minutes to do a body scan

• It provides a high degree of precision with a 2-3 % margin of error.
• This is considered a gold standard for measuring body fat and bone density
• It's painless

Check with your doctor to see if this is right for you and call your insurance company as they may cover it. The cost is usually about $100.

Hydrostatic Weighing

This is just a fancy way of saying underwater weighing. Like DEXA, this test is one of the more accurate ones. How it works:

• You sit on a scale inside a tank of water and blow out as much air as you can
• You are dunked underwater, where you blow out even more air
• Since fat is lighter than water, the more fat you have, the more you'll float. The scale measures underwater weight to figure out body density.
• The margin of error is around 2-3%, but the accuracy depends on the amount of air you expel. You have to blow it ALL out or it won't be as accurate.
• This is a difficult way to measure body fat since it can be uncomfortable and even scary to be dunked underwater with no air in the old lungs.

Many universities offer this test for around $25-$50. Call your local university and ask if they offer this. Fitness Wave offers mobile hydrostatic weighing in Southern California, Nevada and Arizona for $49.95.

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