How DEXA (Body Composition Scans) Work

DEXA works by passing two (dual) very low dose x-ray beams at differing energy levels through the tissues of the body. Fat, muscle and bone each have different attenuating factors, i.e. different levels of absorption due to their unique densities. It is these attenuating factors that allow the DEXA to calculate relative masses of each tissue type.

DEXA Body Composition Scan Preparation

DEXA Body Composition Scan generally has no required preparation. You will only need to fill out a simple questionnaire.

Please inform the radiographer if you have had any surgery on your spine or hips such as a hip replacement.

No preparation is required for this procedure. You do not need to fast and you may take all your medications as usual. There are no tunnels or confined spaces, no injections and the procedure is not painful.

It is helpful, but not essential, to wear loose fitting, comfortable clothing without metal buttons, buckles or zippers. Metal objects interfere with the X-rays and make the results inaccurate. A gown or sheet is usually provided if clothing needs to be removed.

What's involved in having a scan?

To have a scan you simply lie flat on the padded table while the arm of the machine passes over your body.

The scan only take 4 minutes but you need to allow about 15 minutes. You remain clothed during the scan.

Please note, it is not recommended having a scan while pregnant. Having a scan while breastfeeding will not have any adverse effects.   You will be given a printed report at the duration of you scan.  This can be used by your trainer, dietitian or nutritionist to help give you further guidance based on your results.

What will the report show me ?

Your scan report will show the following measurements, accurate to one tenth of a gram:

  • Bone mineral – density, mass and area
  • Muscle – density, mass and area
  • Fat – density, mass and area
  • Fat %, Lean % and Bone %

How can these results be used ?

A DEXA scan will give you a highly accurate baseline to help you make lifestyle changes to improve your health and reduce your risk for various diseases.

By having your body composition monitored periodically, you will also be able to objectively track your progress towards goals. Quantifying these changes also helps with updating dietary and activity requirements.

Feedback from DEXA scans can also be a powerful motivational tool for this purpose.