This Is The Most Accurate Way To Measure Your Body Fat Percentage

Hint: It's not the scales!

body fat percentage
Image: Victoria Sport

You’re training hard, eating well and you can tell your clothes are getting looser. So, why isn’t the number on the scales going down? Or perhaps its even going up! It can be super disheartening when you feel like you’re doing all the right things but the scales don’t reflect it. So, what’s going on?

While there are a few factors that can affect the number on the scales (water weight, that time of the month etc), it could also be that you’ve actually gained muscle and lost body fat. Although muscle weighs more than fat, it takes up less space — so, you’ll look more toned, but the scales won’t budge.

It’s because of this that more and more people are looking beyond the traditional scales to monitor their results. Body composition scans give you a much more comprehensive view of your progress, showing you exactly how much of your weight is fat and how much is muscle and bone.

The only problem is, there are now so many different types of body composition scans it can be hard to know which one to trust.  They all have varying margins of error, one may tell you you’re 17% body fat, while the next will say you’re 27% – on the same day! While the most important thing is to stick with the same one so you can accurately track your progress, we’ve put together a guide to the most common body composition methods.

1. Skin calipers

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Calipers work by pulling subcutaneous fat (fat directly under the skin) away from the muscle with the tongs at their ends. Several predetermined sites like the stomach and thighs are measured by a gauge that records the thickness of the pinch created by the tongs. An equation can then be used to determine body fat percentage.

Accuracy: While this method is commonly used in gyms, it’s not the most accurate test — because it only measures from a few sites, doesn’t take into account the fat deep under the surface and depends a lot on the skill of the person doing the test. However, if the same person does the test each time, it’s a good way to measure progress.

2. Bioelectrical Impedance

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If you’ve ever used a body fat scale, handheld device or wristband, it probably used the Bioelectrical impedance method. This works by sending tiny electrical impulses through the body and measuring how quickly they return. Since lean tissue conducts electrical impulses quicker than fatty tissue, a faster response time means a leaner physique.

Accuracy: While this is one of the most readily available methods, it’s also one of the least accurate. The reading is affected by things like hydration, food intake and body temperature and it can over or under-estimate your body fat percentage by up to 8%.

3. Hydrostatic weighing

While this method looks a little scary, it’s actually remarkably accurate. It involves sitting on a scale underwater and blowing out as much air as you can. It’s based upon the Archimedes Principle, which states that the buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object. In simple terms — fat floats and muscle sinks. So, a person with more body fat will float more and weigh less underwater, while someone with more muscle will weigh more underwater.

Accuracy: 2-3%, when carried out correctly.

4. DEXA Scan

The DEXA scan is widely considered the gold standard of body composition tests. Using X-Ray technology, it not only estimates your lean tissue and bone mineral, it also breaks it down it by body segment so you can see its located. It involves lying down while the machine scans your body and it only takes around 15 minutes. While DEXA machines used to only be available in hospitals, clinics are beginning to pop up across the country.

Accuracy: The DEXA scan is thought to be the most accurate body scan, with a 1% margin of error.

5. 3D Body Scanners

This is the newest type of body scan and also the most high-tech. Companies like ShapeScale and Naked use a volume/weight measurement similar to hydrostatic weighing to calculate your body composition. They also use cameras that circle around you to create a 3D image of you that appears in the app, so you can see where you’ve lost or gained body fat or muscle. They’re quite pricey, both retailing at around $1000 AU. But as they’re at-home devices and you can easily spend $100 on each DEXA scan, it could work out to be quite good value.

Accuracy: Both companies claim that their devices have a 2-3% error margin (around the same as hydrostatic weighing) but as they don’t launch until next year, it’s hard to say for sure.