A quick Google search will reveal numerous body composition tests, which claim to be able to tell you how much of your body is and isn’t fat.
The non-fat part of your body is usually referred to as lean body mass or fat-free mass, which includes muscle, bone and organs. The fat part is body fat.
The problem with all of these tests is that they’re not very accurate. Body fat scales… DEXA scans… the Bod Pod… underwater weighing… all come with a large margin of error.
None can be relied on to provide reliable, practical information that you can use to make better decisions about what to eat and how to train.
How Is Body Fat Measured?
There’s no way to actually measure how your body composition changes over time. The only real way to measure your body composition is through carcass analysis, where all the fat is stripped out from a dead body and weighed.
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So if you wanted to measure how your body composition changes over time, somebody would need to kill you, strip out all your fat, and work out how much of the remainder came from muscle.
Then they’d need to invent time travel, go back in time to before you were dead, and put you on a training program for a period of time, be it three months, six months, one year or whatever.
Then they’d need to kill you again, and analyze your carcass to see how your body composition changed over time.
The 4-Compartment Model
The second most accurate method is something called the 4-compartment model, or 4C model for short.
The 4C model is an expensive method of measuring body composition that divides the body into four components (mineral, water, fat, and protein) and measures each one independently.
Short of killing someone, stripping off their fat and weighing it, the 4C model is as good as you’re going to get. It’s currently the benchmark test for body composition and the gold standard against which other body composition tests are measured.
A body composition test is less of a measurement than it is an estimate. A rough guess about what your body composition really is.
The BodPod… DEXA… underwater weighing… none do a very good job of tracking individual changes over time (as opposed to measuring group averages) when compared to the 4-compartment model [1, 2, 3].
If you really want some kind of “objective” way to measure how much fat you’re losing over time, I’d suggest using skinfold calipers in the way I’ve described here.
See Also: The Flat Belly Cheat Sheet
If you want less flab and more muscle when you look down at your abs (or where they should be), check out The Flat Belly Cheat Sheet.
It's a “cut the waffle and just tell me what to do” PDF that tells you exactly how to lose your gut and get back in shape. To get a copy of the cheat sheet sent to you, please enter your email address in the box below, and hit the “send it now” button.
About the Author
Christian Finn is an exercise scientist and former “trainer to the trainers” based in the UK. He holds a masters degree in exercise science, and has been featured in or contributed to major media on two continents, including the BBC and Sunday Times in the U.K. and Men’s Health and Men’s Fitness in the U.S.
