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4 Ways To Measure Body Fat

May 11th, 2008 · 1 Comment ·


As mentioned in the article of Why Measuring Body Fat Is More Important Than Body Weight, weight alone does not distinguish whether the weight comes from fat or muscle. Knowing body fat is more helpful in weight control.

There are four ways to measure body fat:

  1. DEXA scan
  2. Bioelectrical Impedance (Home Body Fat Scales)
  3. Skinfold Calipers (Callipers)
  4. Hydrostatic Weighing

Each of these body fat calculation method has advantages and disadvantages.

1) DEXA Scan (Dual energy X-ray absorptiometry)
The most accurate way to measure body fat is to use a DEXA scan. This is a special x-ray device that can measure body fat. This test is used to measure bone density, but it also measures body fat percentage as well as where most of your fat is.


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 to 20 minutes to do a body scan. It provides a high degree of precision with a 2 to 3 % margin of error. This is considered a gold standard for measuring body fat and bone density. It is painless too.

2) Bioelectrical Impedance (Home Body Fat Scales)
Body fat scales claim to measure body fat quickly and conveniently. These body fat scales use the Bioelectrical Impedance method to measure your body fat percentage. A low-level electrical current is passed through the body and the “impedance” or opposition to the flow of current is measured. The result is used in conjunction with your weight and other factors to determine your body fat percentage.


Sad to say, our body’s “impedance level” can be altered by many factors besides body fat. For instance, the amount of water in our body, our skin temperature and recent physical activity may adversely affect the results. Therefore, only by following strict rules can, we may be able to get an accurate measurement of our body fat using these scales.

The most important rules to observe in order to make a more accurate calculation of our body fat are:

  • Not to eat or drink for 4 hours before the body fat measurement test.
  • Not to exercise for 12 hours before the test.

How it works:

  • Either using a handhold 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 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 are dehydrated, your body fat percentage will read higher than it is.
  • Be sure you test at the same time of day, preferably first thing in the morning before breakfast, but after a glass of water.

Omron Body Fat Monitor and Scale HB-400 and Omron HBF-306C Fat Loss Monitor operate based on Bioelectrical Impedance concept.

3) Skinfold Calipers
This method is also known as Pinch Test. Measuring body fat with a set of body fat calipers is the most cost effective way to determine fat levels. Calipers are a pincher-like device that are used to pinch your skin in specific locations on your body, such as your waist.


Skinfold measurements are available at most gyms or health clubs that have certified fitness instructors. Skinfold measurements are only reliable if they are done correctly by experienced people. It depends on the skill of the tester at separating your fat from your muscle and finding the right spots to pinch.

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 may not be accurate as compared to the above two methods. Also, it can be painful when the caliper pinches on your skin.

You can buy your own calipers. If you are 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.

4) Using Hydrostatic Weighing to Measure Body Fat
Hydrostatic weighing (underwater weighing) is another accurate way to calculate body fat – that is, if you can find a hydrostatic weighing tank.


Its concept in measuring body fat is based on Archimedes Principle. (Archimedes’ Principle is the law of buoyancy. The principle states that “any body partially or completely submerged in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the body).

Your examiner first calculates your body density by measuring the amount of water you displace when you immerse yourself in water. Then a formula is used to calculate body fat based on your body density. The challenge is finding a facility which has a hydrostatic weighing tank. Some universities have this facility.

This is just a fancy way of saying underwater weighing.


How underwater weighing 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 will float.
  • The scale measures underwater weight to figure out body density.
  • The margin of error is around 2 to 3%, but the accuracy depends on the amount of air you expel.
  • You have to blow the air all out or the measurement may not 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.

Now, you have learnt four methods are available to measure your body fat. Tracking your body fat is the best way to make sure that you are losing fat and gaining muscle. I normally get my gym fitness instructor to use caliper for the measurement. You do not have to measure your body fat too often since the figure does not change every day. Do it once every two months is good enough.



Category: Weight Loss

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1 response so far ↓
  • barbara matranga // Nov 2, 2010 at 10:22 AM

    It is the body fat percentage that is very important to how you look and feel and for you overall health. The scale is good but knowing how much body fat you have on your body at any age. it is very good. and if the jeans fit, that is what matters. toned and buffed and not feeling stuffed is a good feeling. no matter what the scale says.
    this is a great site to gain knowledge, I highly suggest it.

    Barbara Matranga

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