How DEXA Is Used

Who performs the scan

DEXA (dual-energy X-ray absorptiometry) scans are performed by a clinic on a clinical scanner, by a technician, and reported back as a formal document. They are not self-administered and not estimated.

What a DEXA reports

• Total and regional fat mass
• Total and regional lean mass
• Bone mineral density and content
• Visceral adipose tissue estimate
• Left-versus-right and limb-versus-trunk distribution

How often

Scans are spaced months apart. A DEXA is a low-dose X-ray, so repeating it frequently is neither sensible nor informative — body composition does not move meaningfully week to week, whatever a smart scale suggests.

Why it is the reference

The scale reports body composition every day but infers it from electrical impedance and is sensitive to hydration. DEXA measures tissue directly. So DEXA anchors the true value at a few points across the year, and the daily scale figures are read as a trend between those anchors rather than as absolute numbers.

Scans are taken under the same conditions each time — fasted, morning, similar hydration — because DEXA is not immune to hydration either.

What this measurement cannot tell you

A single reading is close to meaningless on its own. What matters is the shape of the series across a year, read alongside the fasting schedule, sleep, training and the notes for that week. Nothing on this site is presented as evidence that fasting caused a change: this is one person, with no control condition, and many things change over a year besides the fasting days.