Triathlon Goddess: How to Measure Body Fat

by Ben Greenfield
Get-Fit Guy

There are so many ways to measure body fat that the options can be confusing. From skin calipers and scales and circumferences to underwater weighing, bod pods, and full body scans, it can be tough to really know what is accurate, reliable, and practical for your needs. So in this episode, you’ll learn 6 ways to measure your body fat and why you should measure it in the first place.

What Is Body Fat Percentage?

There are two different types of body fat. The first, your essential fat, is necessary for you to stay alive; essential fat levels are about 3-5% in men and 8-12% in women. When I was a bodybuilder, my total body fat dropped down to 2%, which meant my essential fat was very low, and I experienced mood swings, joint pain, and loss of sex drive and appetite--along with other issues that correlate to a low essential body fat. Needless to say, as soon as I was done bodybuilding I got my hands on some ice cream and brought myself back up to a healthy body fat level.

The second type of body fat is your storage fat, which is also know as adipose tissue. Some storage fat protects your organs or provides insulation, but for many people, it’s just annoying storage energy waiting to be burned.

Why Measure Body Fat?

If you know your body fat levels, then you have a number that you can use as a goal. For example, if you use any of the information in this article to find that your body fat percentage is 30%, and you weight 170 pounds, then you can calculate that 30% of 170 pounds is 51 pounds, and learn that’s how many pounds of fat you have on your body. You can then make a goal to lose 10 pounds of fat in 5 weeks. If you don’t lose any muscle along the way, then you’d weight 160 pounds, you’d have 41 pounds of body fat (51-10=41) and your new body fat percentage would be 25%.

But what if you do gain muscle? If you’re just tracking your body weight, then you may be disappointed because the scale might show that you’re not losing many pounds, even though your body fat levels are going down. By using a body fat scale, you can track what is happening with your body fat, even if your body weight is not changing. Since muscle takes up far less space than fat, a gain in lean muscle accompanied by a loss in body fat can result in a smaller waistline, flatter stomach, and a decrease in clothing size!

How to Measure Body Fat

Now that you know what body fat percentage is and why you should measure it, here are the 6 ways you can check your body fat:

Underwater weighing. Also know as hydrodensitometry, you’ll usually find this option at a university or laboratory. As the name implies, you are literally dunked underwater. While underwater, you let all the air out of your lungs and your body density is calculated. Body density can then be used to calculate body fat. Underwater weighing is considered a “gold-standard” measurement and is very accurate--but let’s face it: unless winning money at the fair is involved, who wants to strip to their skivvies and get dunked in a big tub of water?
Calipers. Also known as “the pinch method,” a skinfold caliper measurement involves pinching and measuring the fat under your skin on three to seven different places on your body, and then using the thicknesses on these pinches of fat to calculate body fat percentage. Since it’s quick and convenient, you’ll often find personal trainers at gyms using these measurements. Unfortunately, unless you do many, many caliper measurements, it is easy to grab an inaccurate pinch of fat, and vastly over-or underestimate body fat, especially in overweight or obese individuals. If you use this method, make sure the person measuring you really knows what they’re doing--ask them how many times they’ve done caliper testing.
DEXA. DEXA, which stands for dual energy X-Ray absorptiometry, is a full body scan usually used to measure bone density that can also be used to measure body fat and show exactly where the fat is distributed. It is one of the more costly methods of measurement and probably not an option for people who like to avoid X-ray radiation; but if you’re been diagnosed with a chronic disease related to an obese or overweight condition, you may be able to get your health insurance to cover the cost. Though less common than DEXA, other full body scanning devices that can measure body fat include Magnetic Resonance Imaging (MRI), Total Body Electrical Conductivity (TOBEC) and Computed Tomography (CT scan).
NIR. In NIR (Near Infrared Interactance), a fiber optic probe is held against your skin (usually on your biceps), a painless light is used to penetrate the tissues, and the light is then reflected off your bones back into the detector, which approximates your body fat based on a prediction equation that also takes into consideration your height, weight, body type, and level of activity. Although simple and non-invasive, this method can have a high degree of error in people with very high or very low body fat percentages, and it also requires a very experienced technician. Your level of hydration and skin color can also affect the accuracy of this measurement.
BodPod. An expensive, space-age looking pod that can be found at many fancier health clubs, a BodPod uses sensors to measure how much air your body displaces while you sit inside the small chamber. This information is then used to determine your body density and then estimate your body fat.
BIA. Somewhat similar to NIR, BIA, which stands for analysis, sends a painless electrical signal into your body, whichpasses through fat, muscle, and water at different speeds. The speed is then combined with your sex, height, weight, and activity levels to approximate your body fat percentage. Once again, if you’re dehydrated, over-hydrated, or very skinny or very overweight, this measurement can be inaccurate--but it is very commonly used in body fat scales or handheld devices, because it is relatively inexpensive and portable.