Measurement Tools — DEXA

What It Is


Dual energy X-ray absorptiometry (DEXA) is based on dividing the body into three compartments: total body mineral (from bones), fat-free soft (lean) mass, and fat tissue mass.

  • The person is scanned with photons that are generated by two low-dose x-rays at different energy levels.
  • The body's absorption of the photons at the two levels is measured.
  • The ratios arecan be then used to predict total body fat, fat-free mass, and total body bone mineral.

Equipment Used

A whole body scanner with the x-ray sources mounted beneath a table and a detector overhead.

How It's Done

  • Person lies on a table and is scanned.
  • Measurements take about 10 - 20 minutes.


  • It's considered a reference standard, and the latest body composition research uses this method.
  • It's precise, accurate, and reliable.
  • It's safe.
  • It's noninvasive.
  • It can be used to determine body fat distribution.


  • The narrow table limits its use with heavier people.
  • The equipment is expensive.
  • It's used primarily in laboratory settings.

Illustration courtesy Tanita Corporation of America Inc.

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