Measurement
Biomarker Basics: Which Numbers Are Worth Tracking
A plain-language framework for blood panels, body composition and fitness testing — what each measure tells you, and how often re-testing is useful.
8 min read · Published 20 Aug 2026
Testing & diagnostics
DEXA and Body Composition Testing in Marbella
Body composition tells you what a bodyweight change is made of. Two people losing the same four kilos can have opposite outcomes depending on how much of it was muscle.
DEXA is the most detailed option generally available privately; it is not the only useful one.
What DEXA does and does not measure
A DEXA (DXA) scan uses two low-dose X-ray energies to estimate fat mass, lean soft tissue and bone mineral density, with a regional breakdown by limb and trunk. Radiation dose is very low, but it is not zero, which is one reason to scan deliberately rather than often.
It does not measure muscle quality, hydration status or visceral fat directly beyond an estimate, and results shift with hydration, recent meals and recent training. It is a measurement tool, not a diagnosis.
DEXA, bioimpedance and skinfolds compared
Each method trades accuracy for access. The best one is usually the one you can repeat under identical conditions.
- DEXA: highest detail, includes bone density, needs a clinic appointment, highest cost per scan
- Bioimpedance (gym or home scales): instant and cheap, strongly affected by hydration, best read as a trend not an absolute
- Skinfolds by a trained practitioner: inexpensive and surprisingly reliable for tracking change when the same person measures each time
- Tape measurements and photographs: free, and adequate for most people's actual decisions
How often to re-test
Body composition moves slowly. Scanning every few weeks mostly measures hydration and measurement error.
Three to six months is a reasonable interval for most people, or at the start and end of a defined training or nutrition block. Standardise the conditions each time: morning, fasted, no training the day before, similar hydration and no alcohol in the previous 24 hours.
Know this coast better than we do?
We only publish what we can stand behind. If you have first-hand local knowledge worth adding to this page, tell us and we will research it.
Contribute local knowledgeEducational content only. Nothing on this site is medical advice, and no product is offered to diagnose, treat, cure or prevent any condition.