Earlier this week, I came across a forum post about a guy who got a DEXA scan for the first time.
He’d estimated his own level of body fat, based on the way he looked in the mirror, at around 18-20%.
But the DEXA scan told him that his body fat was 28.6%, and he couldn’t understand why it was so high.
One of the replies he got suggested ignoring the number, and focusing instead on how that number changes over time.
In other words, it doesn’t matter if DEXA is off by a few percentage points here or there. As long as it’s consistent, you can use it to track your progress over time.
However, DEXA scans aren’t cheap. The guy I was reading about paid $100 for the scan. If he goes back again after a few months, that’s another $100. Two hundred dollars is a lot of money to spend if the results aren’t telling you anything useful.
How accurate are DEXA scans when it comes to tracking your progress over time? Are they worth the money?
Are DEXA Scans Accurate?
The simple answer to this question is no, DEXA scans are not an accurate way to measure your body composition.
That said, no device can accurately measure how much muscle and fat you have.
The only way to truly measure your body fat is to have all of it stripped out, placed on a scale, and weighed. This method is highly accurate. The only downside is that you have be dead in order for it to happen.
A better question to ask yourself is this:
Are DEXA scans accurate enough so that I can use the information to make better decisions about what to eat and how to train?
DEXA does a reasonable job at estimating group averages. But, it’s not so good at tracking individual changes in body fat and muscle mass over time .
DEXA might overestimate body fat percentage in half your group by 5%, and underestimate it in the other half by 5%. When looking at the group results, the average error size is zero. But the individual results are way out.
The fact that a body fat test does a good job at estimating group averages doesn’t mean that it’s equally as good at measuring individual progress over time.
What This Means for You
The individual error rate with DEXA is around 5% (although some studies put it much higher).
What does that mean for you?
Let’s say you get a DEXA scan, and it tells you that your body fat percentage is 20%.
You download Muscle Evo, follow the program for a couple of months, and get down to 15% body fat.
But when you go back for another scan, DEXA might tell you that your body fat percentage is still 20%.
Same thing holds true for muscle growth.
Let’s say you gain 5-6 pounds (around 2-3 kg) of muscle. Which, depending on the length of time you’ve been training, could take many months of hard work.
But a DEXA scan might show that you hadn’t gained any muscle at all.
You’d come away with the impression that whatever you’d been doing to generate those results didn’t work, when actually it did.
And you run the risk of ditching a training and nutrition program that’s working and replacing it with one that’s less effective.
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 get rid of belly fat. To get a copy of the cheat sheet sent to you, please click or tap here to enter your email address.
ABOUT THE AUTHORChristian Finn is the nation’s leading authority on science-based, joint-friendly ways to build muscle. A former "trainer to the trainers," 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.