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.
What prompted me to write this was an email I got recently from a Muscle Evo reader.
He wrote:
“I use body fat scales to get some sort of objective measure of my body composition. It’s been measured at 10%. I’m stuck on where my focus should be. I’m sort of anticipating you would advise me to focus on muscle gain given that my body fat is below 10%.
“But when I look down at my stomach, it definitely doesn’t feel like I have less than 10% body fat. I feel like I probably have a reasonable set of abs underneath but they’re not visible because of the surplus fat. So I keep pendulating between fat loss and muscle gaining both in my workout programs and my nutrition, going round in circles achieving not a great deal for a lot of effort.”
What do you do when the results from a body composition test leave you confused about what your goal should be?
I’ll get to that in a moment.
First, imagine you’re sat at home.
The phone rings.
You answer it.
It’s your best friend.
He’s lost.
He doesn’t have a sat nav or a map.
And he needs your help to get himself “unlost” again.
After telling him what an idiot he’s been for setting off without a sat nav or a map, what’s the first thing you ask him?
It’s probably going to be something along the lines of, “do you know where you are right now?”
That’s because knowing where you are right now is a necessary first step in order to get where you want to go.
All of which brings me to the main problem with body fat scales – they’re highly unreliable when it comes to telling you where you are right now in terms of body composition. It’s a subject I’ve covered in more detail here.
The problem isn’t one that’s limited to body fat scales.
What Is the Most Accurate Body Composition Test?
The only real way to measure your body composition is to have all of your body fat stripped out, placed on a scale, and weighed. This method is highly accurate. The only downside is that you have be dead for it to happen.
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 a prediction. And just like the words of wisdom that come from economists, football pundits and stock market analysts, many of those predictions will turn out to be wrong.
“Regardless of how the measurement is done, we end up with a prediction of what we think your body fat would be if we were to kill you, take all of the fat, and weigh it,” writes James Krieger in The Pitfalls of Body Fat Measurement.
“This prediction has an error associated with it, and the size of this error varies depending upon which technique we used to take the measurement. While some techniques have smaller errors than others, even the best techniques have pretty large errors… larger than what most people realize.”
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, which is currently the “gold standard” where body composition testing is concerned [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.
Why I Don’t Recommend Body Composition Testing
A body composition test is a guess about how much fat you have. It’s a guess that looks very scientific and official because it comes dressed up in “state of the art” equipment and complicated equations.
But it’s still a guess.
So here’s the simple way to decide what your goal should be. Take a look in the mirror. If you see more fat than you’d like, then focus on getting rid of it. Once that’s done, then you can focus on something else.
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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.