How to Measure Body Fat

For most people, seeing the number on the scale decrease over time is enough motivation to continue with a consistent workout and nutrition plan. The problem with relying on just the scale is that there is no way of knowing just how much of that weight loss is water, fat or muscle tissue.

Water loss can be deceptive because even though our weight may go down, this can fluctuate immensely depending on the time of day, the time of month, how much coffee we’ve had, and a number of other factors.

Obviously we never want to lose muscle tissue since it is so valuable and requires a lot of hard work and time to build. While some muscle loss may be inevitable when starting out on a calorie controlled plan, doing things properly certainly can minimize it.

This is when body fat measurements can come in handy if you are super serious about getting real, honest results. Not all tools used to measure body fat percentage are equal however. Not even close.

Tanita Scales

Tanita scales are fancy, expensive versions of the in home bathroom scale that offer a number of digital upgrades including body fat percentage measurements. These scales use Bioelectrical Impedance Analysis to determine how much fat your are carrying in comparison to lean tissue.

A very low, electrical current is sent through the body and carried through muscle tissue and liquid with ease but comes to a halt when it reaches fat. Body fat impedes the bioelectrical current. Using this measurement in a formula with a persons weight, height and gender, the percentage of body fat can be calculated.

While Tanita scales may be somewhat useful for an estimation of progress over time, they can fall victim to inaccuracy depending on how hydrated or possibly dehydrated a person is. The best way to avoid this is to be diligent in using the scale at the same time of day and the same hydration level each time. The margin of error with Tanita scales falls between 2 to 5 percent.


Quite often, if you sign up with a new membership at a gym, they will offer a complimentary body fat assessment. One of the trainers uses the skin fold calipers to pinch a fold of fat on various landmarks over the body.

Calipers are highly inaccurate and although they are a great way to entice new clients, they are probably not worth the time it takes. Body fat measurements using calipers are subject to numerous variables.

First of all, the skill of the person performing the test will be of the most concern. Many people are inaccurate with their landmarks and this can make a huge difference in outcomes. Also, if different people are performing the test each time, you are likely to end up having no idea what kind of real progress you are making since each person may perform the test in a slightly different way.

The time of day, hydration levels, the time of month for women and recent vigorous exercise are all variables that can skew test results as well. The margin of error for this method can be anywhere from 3 to 10 percent.

DEXA Measurements

DEXA is an acronym standing for Dual Energy X-ray Absorptiometry. It’s a painless, fairly accurate way to determine both bone mass and body fat percentage. It can also pinpoint the location of fat distribution and problem areas.

It’s far more expensive and less available than the calliper method but is more accurate since there is a reduced risk of human error. The margin of error for this method is an estimated 2 to 3 percent.

Hydrostatic Underwater Weighing

To put things very simply, underwater weighing is based on the principle that muscle and bone are dense and tend to sink whereas fat floats. If you’re fat you’ll weigh less underwater and if you’re lean and muscular you’ll weigh more underwater.

To perform the test, an individual is first weighed on dry land and then placed on a special scale and lowered into the water. Remaining motionless and having exhaled to full capacity, the persons weight is determined and then repeated three times in order to find an average. Certain calculations are then performed to determine body fat percentage. The margin of error is 2 to 3 percent.

The Bod Pod

The bod pod is a capsule that measures body fat much in the same way that hydrostatic weighing is done, only with air displacement as opposed to water. As you sit in the capsule, a predetermined amount of air is forced into the cabin. The air pressure inside will change in proportion to your size. The volume of air that your body is taking up is calculated and with formulations, body fat percentage is calculated.

The accuracy is subject to the type of clothing that is worn during the test, when food was last consumed and when exercise was last performed. The margin of error for this method is anywhere from 2 to 3 percent, similar to the hydrostatic method and the DEXA.

In Summary

There is no doubt that if you consistently follow a balanced, calorie controlled nutrition plan and put the required effort and intensity into a great workout program, you will certainly lose body fat. You don’t even need a body fat percentage test to tell you that, it will be obvious in your clothes and your reflection.

If you’d like more scientific proof of your success that can be seen on paper, then by all means have a body fat test before, during and after your prescribed program. If at all possible, try to go with the most accurate method. While Tanita scales and calliper tests may be inexpensive, they are also the least reliable so your results may not be what you want to see.

If you really want accuracy and can afford the cost of the DEXA, Hydrostatic or Bod Pod tests, these methods will offer a more precise estimate.

In the meantime, remember that without a doubt, calorie control, nutritious eating and intense workouts will get you where you wan to be.

To your success,

Craig Ballantyne, CTT
Certified Turbulence Trainer