How to Measure Your Body Fat

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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.

Calipers (aka, the Pinch Test)

This method uses calipers to measure skinfold thickness at several areas of your body. How it works:

  • An expert pinches your skin at different areas and measures them with calipers.
  • The results are plugged into a formula to determine your body fat.
  • The result is based on the idea that thickness of fat under the skin reflects total body fat.
  • It CAN be as accurate as the methods mentioned about, but usually isn't. It depends on the skill of the tester at separating your fat from your muscle and finding the right spots to pinch.
  • The results can also be skewed if you're older (since fat moves inward with age) or if you are nonwhite since formulas are based on white subjects.
  • This is one of the more accessible ways to check body fat and is generally painless.

You can get tested at most health clubs and universities for little or no cost. You can also buy your own calipers, but I wouldn't get too excited about the results you get.

If you're not skilled at it, the results can be way off. Always make sure you get the same person to test your body fat since results can vary from tester to tester. Where to find body fat calipers.

Bioelectrical Impedance

This is one of the quickest methods of testing body fat using a BIA scale.

  • Either using a handheld scale or standing on a BIA scale, a signal passes either from hand to hand or foot to foot.
  • The faster the signal travels, the more muscle you have.
  • The results are based on the fact that water conducts electricity. Fat contains almost no water while the muscle is about 70% water.
  • This method CAN be accurate (4% margin of error) but the results are affected by hydration, food intake and skin temperature. If you're dehydrated, your body fat percentage will read higher than it is.

This is an easy way to test your body fat. Be sure you test at the same time of day, preferably first thing in the morning before breakfast, but after a glass of water.

Body Mass Index

  • BMI takes into account your weight and height, giving you a number that you compare with a BMI chart.
  • It doesn't give you a body fat percentage but indicates whether you're obese or overweight. For example, if your BMI is 22, that doesn't mean your body fat is 22%.
  • A BMI less than 18.5 indicates underweight
  • A BMI of 25 - 30 is considered overweight
  • A BMI of over 30 is considered obese
  • This calculation isn't as accurate, as it doesn't take into account age or sex. A muscular person may have a high BMI that doesn't reflect actual body composition

Obviously, there are many methods to test your body fat (and many I didn't have time to talk about). Accuracy is important, but all of these methods (if used correctly) can measure body fat within 2-5%. Tracking your body fat is the best way to make sure that you're losing fat and gaining muscle. Just don't test it too often since body fat measurements don't show small changes. Every 4-8 weeks is best.