How to measure body fat percentage.



There are a myriad of ways to measure body fat percentage from the quick and fairly painless to the very (and I mean very) detailed. One method is very different from another and might be extremely accurate, while others have quite the margin of error. To help you navigate the numerous techniques, read on for 6 methods of body fat percentage measurement, in order of accuracy from most accurate to less accurate (but still useful!)

1. Hydrostatic Weighing

Hydrostatic weighing or underwater weighing compares your normal weight (outside the water) to your weight while submerged underwater. Using these two numbers and the density of the water, technicians can accurately measure your density. This number is then used to estimate body composition. This is commonly seen as the “gold standard” by professionals as it has a very high level of accuracy and is commonly used in a research setting. Hydrostatic weighing, however, is quite a bit more expensive to do, and will require that you find a lab in which to do so.

2. DEXA (Dual-Energy X-Ray Absorptiometry)

A DEXA scan simply involves lying on a table for a few quick, dry and painless minutes. You lie still on a table while a machine arm passes over your entire body emitting a high and a low-energy X-ray beam, measuring the absorption of each beam into parts of the body, resulting in readings for bone mineral density, lean and fat mass. DEXA can also break down body composition per limb confirming suspicions that your right bicep is stronger than your left due to years of waitressing. DEXA is extremely accurate – much like hydrostatic weighing – at measuring body composition, however it carries a much higher price tag and will require you to find a lab that has this machine.

3.  Air-Displacement Plethysmography

Air-displacement plethysmography is very similar to underwater weighing.  By sitting in a small machine shaped like an egg which measures how much air you displace, technicians can determine your body density. Just like underwater weighing, your body density is then used to calculate body composition. This has a very slightly higher margin of error than underwater weighing, but is still quite accurate. However these machines aren’t easy to find and involve again a higher price tag.

4. 3D Body Scan

You may see these devices become more accessible this year (2017). Many brands offer at-home devices that scan your body, take circumference measurements of different body parts and track your body fat via a corresponding app. Very close to the margin of error of the DEXA method, these machines can help easily and frequently track progress to keep you motivated finding small changes you may not normally notice in the comfort of your own home. Unlike bioelectrical impedance, you don’t need to worry about hydration, meals or workout times which is also a bonus.

5. Calipers (or as many of my clients lovingly refer to them: “pinchy things”)

The most accessible method for measuring body composition, professionals perform a skin fold assessment using either three, four or seven sites on the body.  After plugging the numbers into a formula, they can estimate body fat percentage. There is a moderate margin of error with this method so in order to minimize error, the testing should be done consistently by the same highly skilled professional each time.

6. Bioelectrical Impedance

This is another more common measure. Don’t worry, even though it sounds scary – you won’t feel a thing. These devices work by sending tiny electrical impulses through the body and measuring how quickly those impulses return. Since lean tissue conducts electrical impulses quicker than fatty tissue, a faster response means a lower body fat. The results from bioelectrical impedance show within seconds and are often found in home weight scales, however there is a moderate margin of error with this method which can be affected by hydration levels, recent meals and workouts – so be sure to follow manufacturer directions to minimize error.

Body fat percentage tracking tips:

  1. Test a maximum of every 4-6 weeks – more frequent testing will likely not reveal many changes .
  2. Stick with the method you choose – although some have a higher margin of error, they are still a very useful and reliable tool given the conditions under which they are used are the same (time of day, day of week, even before or after a bowel movement!)
  3. Don’t make body fat percentage the only focus of training. Are you feeling better? Sleeping better? Eating better? Feeling happier? Those are just as if not more important than body fat percentage alone.

Enjoy this day!


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