DEXA scan vs InBody: what the comparison studies actually found
By The DexaExplained Team · Last verified
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Educational body-composition information, not medical advice. Nothing here diagnoses, treats, or prevents any condition, and this site does not interpret bone-density results. Talk to your clinician about anything on a scan report that concerns you.
If you've had both an InBody scan at the gym and a DEXA scan, you've probably met the problem this page exists for: the two numbers don't match, sometimes by five or more percentage points, and nobody at either front desk can tell you why.
Short version: DEXA measures your tissue; InBody estimates it. They will rarely agree exactly, the gap is larger the further you are from the population average, and the peer-reviewed comparisons consistently side with DEXA as the reference.
How each one works
DEXA passes two low-dose X-ray energies through your body and measures how much each tissue attenuates them. Fat, lean soft tissue, and bone mineral each attenuate differently, which lets the machine build a three-compartment map of your body — including regional data (each arm, each leg, trunk) and, on modern software, a visceral-fat estimate. It's the method research studies use as their body-composition reference, including the national NHANES reference dataset our percentile charts are built on.
InBody is multi-frequency bioelectrical impedance analysis (BIA): a small electrical current travels through your body via hand and foot electrodes, and the device measures the impedance it meets. Lean tissue (mostly water) conducts well; fat doesn't. From impedance at several frequencies plus your height, weight, age, and sex, the machine estimates compartment sizes using proprietary equations. That indirection is where the disagreement comes from: hydration status, a recent meal, a workout, even skin temperature move the estimate.
What the head-to-head studies found
The cleanest recent comparison is Antonio et al. 2019, which put 45 exercise-trained adults through both an InBody 770 and DEXA before and after a four-week diet:
| Measure | Finding |
|---|---|
| Body-fat % (absolute) | InBody read lower than DEXA |
| Fat mass (absolute) | InBody underestimated vs DEXA |
| Fat-free mass (absolute) | InBody overestimated vs DEXA |
| 4-week changes | No significant difference between devices |
That last row matters: the InBody's absolute numbers disagreed with DEXA, but its direction and magnitude of change tracked. A separate comparison in the Journal of Exercise and Nutrition (Bod Pod, InBody 770, DEXA) likewise found the field devices differ from DEXA at the individual level.
The practical differences
| DEXA | InBody | |
|---|---|---|
| What it does | Measures tissue attenuation | Estimates from electrical impedance |
| Typical cost | $40-185 self-pay (full breakdown) | Often free with gym membership; $25-50 standalone |
| Time | 6-10 min lying still | ~1 min standing |
| Regional detail | Arms/legs/trunk, ALMI-grade data | Segmental estimates |
| Visceral fat | Measured estimate (explainer) | Index estimate |
| Sensitive to hydration/meals | Mildly | Strongly |
| Radiation | Very low dose | None |
The honest recommendation
Use them for different jobs:
- DEXA for the measurement. Once or twice a year, same provider, same prep, ideally the same machine. This is the number you compare against published percentiles.
- InBody (or a home body-comp scale) for the trend. Free-to-cheap, frequent, directionally useful. Just never mix devices when judging progress — compare InBody to InBody, DEXA to DEXA.
- Ignore single-scan drama on either device. A number that jumps overnight is hydration, not tissue.
A DEXA scan costs less than most people assume — often under $60 in the ten metros the van services cover.
See real scan prices near you →For between-scan tracking at home, a body-composition smart scale has the same limitation as InBody (it's BIA with fewer electrodes) and the same virtue (trend data every morning). Our accuracy comparison covers where each method sits.
Frequently asked questions
Is InBody as accurate as a DEXA scan?
No. In direct comparisons, multi-frequency bioelectrical impedance devices like the InBody 770 produced significantly different absolute numbers than DEXA — in Antonio et al. 2019, the InBody underestimated fat mass and body-fat percentage and overestimated fat-free mass in trained adults. Where InBody held up was in tracking the direction of change over four weeks. Treat InBody as a trend tool and DEXA as the measurement.
Why does my InBody number differ so much from my DEXA number?
The two devices measure different things. DEXA measures how X-rays attenuate through fat, lean tissue, and bone — it observes tissue directly. InBody passes a small current through your body and estimates composition from impedance plus equations, which makes it sensitive to hydration, food, recent exercise, and the assumptions in its equations. Gaps of several percentage points in body fat between the two are routine in the published comparisons.
Is an InBody scan ever the better choice?
For frequent, cheap, directional feedback, yes. Many gyms include InBody scans free with membership, they take 60 seconds, and the Antonio 2019 data suggests changes track reasonably even when absolute values are off. A sensible pattern: DEXA once or twice a year for the real numbers, InBody or a body-comp scale in between for trend.