DEXA vs. InBody: Which Body Composition Test Is Actually Accurate?
Your gym might offer free InBody scans. But if you're serious about tracking fat loss and muscle preservation, accuracy matters. Here's why DEXA is the clinical gold standard—and when InBody might be "good enough."
Accuracy Comparison
Not all body composition methods are created equal. Here's how they compare for body fat measurement.
Higher accuracy = more reliable tracking of changes over time
How They Work
DEXA and InBody use fundamentally different technologies to measure your body.
DEXA (Dual-Energy X-ray Absorptiometry)
DEXA uses two low-energy X-ray beams at different frequencies. Different tissues (fat, muscle, bone) absorb these beams differently, allowing direct measurement of tissue composition throughout your entire body.
Originally developed for bone density measurement, DEXA became the gold standard for body composition because it directly measures tissue density rather than estimating it.
- Direct measurement via X-ray technology
- Separate readings for fat, lean mass, and bone
- Regional analysis (arms, legs, trunk)
- Visceral fat measurement (VAT)
- Not affected by hydration status
InBody (Bioelectrical Impedance Analysis)
InBody sends small electrical currents through your body via hand and foot electrodes. It measures how quickly those currents travel—fat slows electricity, while muscle and water conduct it faster.
Using proprietary algorithms, InBody estimates body composition based on impedance patterns. It's fast and convenient, but it's calculating, not measuring.
- Estimates based on electrical resistance
- Highly affected by hydration status
- Can vary by 3-5% same day based on food/water
- Uses population-based algorithms
- May not account for individual variation
Side-by-Side Comparison
How DEXA and InBody compare across key factors for body composition testing.
| Factor | DEXA Scan | InBody |
|---|---|---|
| Body Fat Accuracy | ±1-2% | ±5-8% |
| Measurement Method | Direct measurement (X-ray) | Estimation (electrical impedance) |
| Affected by Hydration | ✓ No | ✗ Significantly |
| Affected by Recent Meals | ✓ Minimal | ✗ Yes |
| Regional Body Analysis | ✓ Yes (detailed) | ✓ Yes (estimated) |
| Visceral Fat Measurement | ✓ Direct measurement | ✗ Estimated only |
| Bone Density | ✓ Yes | ✗ No |
| Scan Time | 7-10 minutes | ~1 minute |
| Equipment Cost | $50,000-100,000+ | $5,000-15,000 |
| Radiation | Very low (0.001 mSv) | None |
| Clinical Use | Medical gold standard | Fitness/gym settings |
Why Accuracy Matters: A Real Example
Here's how the accuracy difference affects tracking your progress.
You're 200 lbs with True Body Fat of 30%
DEXA Reading
InBody Reading
The problem: If InBody says you went from 30% to 27% body fat, you might have actually lost fat—or the machine just read you differently because you were more hydrated. With DEXA, a 3% change is real, measurable progress.
When to Use Each
Both have their place. Here's when each method makes sense.
Choose DEXA When:
- You're on a medical weight loss program and need accurate tracking
- You want to verify you're losing fat, not muscle
- You're monitoring body recomposition during hormone therapy
- You need baseline data before starting a new protocol
- You want visceral fat and bone density data
- Tracking progress every 8-12 weeks
- Making decisions based on the data (adjusting nutrition, medication)
InBody May Be Sufficient When:
- You want rough monthly progress checks
- It's free at your gym and you understand the limitations
- You're looking for general trends over time
- You use it under consistent conditions (same time, hydration)
- You don't need clinical-grade precision
- You're using it alongside other metrics (scale, measurements)
Frequently Asked Questions
Yes. DEXA has ±1-2% accuracy for body fat percentage, while InBody has ±5-8%. That means InBody can be off by 6-16% in either direction. For tracking real changes, DEXA allows us to detect fat loss or muscle gain as small as 1-2 pounds.
Cost and convenience. InBody machines cost $5,000-15,000 vs. $50,000+ for DEXA. They require no medical oversight, take about a minute, and don't use radiation. For gyms, it's a value-add for members. But for serious tracking, the accuracy difference matters.
Absolutely. InBody measures electrical impedance—and water conducts electricity. Being dehydrated can make you appear 3-5% higher body fat. Being over-hydrated (or having eaten recently) can make you appear leaner. Same person, same day, different readings.
Yes. DEXA uses about 0.001 mSv of radiation per scan. For comparison: a chest X-ray is 100x more, a cross-country flight is 40x more, and natural daily background radiation is about 10x more. It's completely safe for regular monitoring every 8-12 weeks.
For weight loss patients, every 8-12 weeks is ideal. This allows enough time to see meaningful changes (2-4% body fat) while enabling protocol adjustments if progress stalls. More frequent scanning doesn't provide additional actionable data.
Ready to Know Your Real Numbers?
Stop guessing with gym estimates. Get precise, medical-grade body composition data with an in-house DEXA scan at Highland Longevity.