InBody vs DEXA Scan: Which Body Composition Test Do You Need?
An InBody scan uses a small electrical current to estimate how much of your body is water, muscle and fat. A DEXA scan uses low-dose X-rays to measure bone, fat and lean tissue directly, region by region. DEXA is generally regarded as the more precise of the two and is the one used in research and, by the NHS, for bone density. InBody is quicker, involves no radiation and is easy to repeat often, which makes it better for tracking change over a training programme. If you want a detailed one-off picture, including bone density, choose DEXA. If you want to see whether your training is working month to month, InBody is usually the practical choice.
Here is how each works, what it can and cannot tell you, and how to get useful information from either.
How an InBody scan works
You stand barefoot on metal foot plates and hold metal hand grips. The machine passes a very small electrical current through your body at several frequencies and measures the resistance it meets, known as impedance. Water conducts electricity well and fat does not, so the readings allow the machine to estimate total body water. From that, using equations built on reference data, it estimates lean mass, muscle and fat.
Because it has electrodes at both hands and both feet, the InBody can also estimate each arm, each leg and the trunk separately. The scan takes about a minute. We explain the full process in what an InBody scan is.
How a DEXA scan works
DEXA stands for dual-energy X-ray absorptiometry. You lie on a padded table while a scanning arm passes over you. Two X-ray beams at different energies pass through your body, and because bone, fat and lean tissue absorb them differently, the machine can separate the three.
The NHS uses DEXA to measure bone density, usually to assess the risk of osteoporosis. The radiation dose is very small; the NHS page on bone density scans explains what happens and who is referred. Body composition DEXA scans for fitness purposes are offered privately by some clinics.
Side by side
| Factor | InBody | DEXA |
|---|---|---|
| Method | Electrical impedance | Low-dose X-ray |
| What it measures directly | Resistance to current, from which water is estimated | Bone, fat and lean tissue |
| Bone density | No (gives a mineral estimate only) | Yes |
| Sensitivity to hydration and food | High | Lower, though not zero |
| Radiation | None | Very small dose |
| Time | About a minute | Several minutes lying still |
| How often it is sensible | Every few weeks | A few times a year at most |
| Where you find it | Gyms, studios, clinics | Hospitals and specialist clinics |
Where DEXA is stronger
- Precision. DEXA measures tissue more directly, so it is less thrown off by a glass of water or a salty dinner.
- Bone density. InBody cannot assess bone health in any meaningful clinical way. If bone density is your concern, that is a conversation with your GP, not a gym test.
- Regional detail. DEXA gives a detailed breakdown of where fat and lean tissue sit, including estimates of fat around the abdomen.
Where InBody is stronger
- Repeatability. No radiation means you can test every four to six weeks without concern, which is what tracking a programme needs.
- Convenience. A minute on the scanner at the start of a session versus a separate appointment at a clinic.
- Hydration data. InBody reports total body water and how it is distributed, which DEXA does not focus on. Our post on InBody body water explains those numbers.
Neither is perfect
It is worth being clear that no body composition test outside a research lab gives you a perfect answer. DEXA results can vary slightly between machines and manufacturers, and a large meal or a lot of fluid can still nudge them. InBody readings shift with hydration, recent exercise, food, alcohol and, for women, the menstrual cycle.
The consequence is the same for both: compare like with like. Use the same machine, at the same time of day, under the same conditions. A change between two scans on the same device is far more meaningful than the absolute number on any one of them. Our guide to InBody accuracy lists the things that skew a reading.
Which should you choose?
- You want to know if your training is working: InBody, repeated under consistent conditions every four to eight weeks.
- You want a detailed baseline before a major change: a DEXA at the start and end, with InBody scans in between, is a sensible combination.
- You are worried about bone health: speak to your GP. A fitness body composition scan is not a substitute for a clinical assessment.
- You just want a rough idea of where you stand: either will do; InBody is simpler to access.
Who should not use an InBody scan
Because the scanner passes a current through the body, people with a pacemaker or other implanted electronic medical device should not use it. Most manufacturers also advise against testing during pregnancy. If you have a heart condition or any implanted device, check with your GP first. DEXA uses radiation, so it is also generally avoided during pregnancy.
How we use the InBody in the studio
We have an InBody scanner in the studio on Archway Road, and we use it as one input among several. Strength numbers, how your clothes fit, energy, sleep and simple tape measurements all matter too. A scan every few weeks, under the same conditions, gives a reasonable trend line. We do not treat a single reading as a verdict. You can read more about how scans fit into a programme on our personal training in Highgate page.
Questions we get asked
Why does my InBody body fat differ from my DEXA result?
They use different methods and different assumptions. A gap of a few percentage points is common. Track each method against itself rather than against the other.
Is a DEXA scan safe?
The radiation dose is very small, which is why the NHS uses it routinely for bone density. It is still sensible not to repeat it more often than you need.
How often should I have an InBody scan?
Every four to eight weeks is enough to see real change rather than day-to-day noise.
Is the InBody included in training?
Details of what is included, and prices, are on the personal training page.
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The Highgate House, Archway Road, Highgate, London N6.
