What is a DEXA scan and how does it measure body composition?
What is a DEXA scan and how does it measure body composition?
Overview
Dual Energy X-Ray Absorptiometry (DEXA) is an imaging technology primarily known for measuring bone mineral density. It is also considered one of the most accurate methods available for estimating body composition, with accuracy comparable to MRI and CT scanning.
How It Works
- A DEXA scanner directs an X-ray beam at the body and uses algorithms to distinguish bone from soft tissue.
- Results provide detailed data on bone mineral content, fat mass, and lean mass.
- DEXA is considered accurate to the four-compartment model — a gold-standard approach that typically requires several separate testing devices.
- DEXA has been demonstrated to accurately estimate visceral fat.
Known Limitations
- Hydration assumption: DEXA assumes fat-free tissue hydration is constant at 73%. In practice, individual hydration can range from 67–85%. If a subject is more hydrated than average, DEXA will overestimate fat content.
- Manufacturer variability: Measurements can differ between DEXA machines from different manufacturers. For consistent tracking over time, use the same device at each assessment.
- Like all body composition methods, DEXA produces an estimate, not an absolute measurement.
Notes
- DEXA is an X-ray technology and does emit a small amount of radiation. However, the dose is very low — roughly equivalent to one day or less of natural background radiation exposure. By comparison, a CT scan can deliver the equivalent of several years of background radiation.
- DEXA scanners are expensive and are generally found only in research institutions and hospital settings, making routine access limited for most fitness and wellness professionals.
- When available, DEXA can be a valuable complementary tool alongside a Styku 3D body scan, providing additional detail on bone mineral density that 3D scanning alone cannot measure.
If this resolves your issue, no further action is needed.
If the problem persists, contact support and include: the assessment method being compared, and the specific measurement discrepancy you are observing.
Applies to: All Styku configurations — general health tech assessment reference material