DXA/DEXA beats BMI: Using an X-ray Exam to Measure Body Composition & Fat Loss

Dual-energy X-ray absorptiometry (DXA or DEXA) is a means of measuring bone density, but a recent article in the Wall Street Journal is highlighting another way in which the imaging exam can be used to benefit your health.

DXA bone density scan is an examination that uses an enhanced form of X-ray technology to measure bone mineral density most commonly in the lower spine and hips.  It is the most accurate method available for the diagnosis of osteoporosis and is also considered an accurate estimator of fracture risk.

In addition to evaluating bone mineral density, the whole-body scan can also be used to measure total body composition and fat content with a high degree of accuracy. In other words, DXA gives a detailed snapshot of your body composition, including how your body weight breaks down into fat, bone and lean tissue. New research shows that the scan is highly accurate compared with most other methods for determining body composition and highly useful for tracking change in muscle and fat over time.

Currently, body-mass index (BMI) is used as the leading measure of being overweight, but the calculation, based on height and weight, can be misleading. In fact, an abstract 50-patient study presented at the annual meeting of the North American Menopause Society reported that 18.5 percent of women with normal BMI had excess fat, visible on DXA.

Used incrementally DXA scans tell a more accurate story than BMI, in terms of progress for muscle development and fat loss. The scans takes 3 to 12 minutes, depending on the machine and body size, and afterwards patients receive a report detailing mass of bones, fat and lean tissues (including organs and muscle) broken out individually.

John A. Shepherd, Associated Professor of Radiology and Director of the Body Composition, Exercise Physiology and Energy Metabolism laboratory at UCSF uses DXA regularly and has seen the benefits of the technique. Along with information about the body as a whole, “the DXA report shows the amount of fat and lean tissue in each body part, such as the right arm or left leg—information that can be helpful for athletes to see if an injured limb is regaining muscle,” says Dr. Shepherd.  In addition, the exam estimates for the amount of visceral fat in patients, a measure that can help predict risk for diabetes and cardiovascular disease.

At UCSF we are currently offering DXA scans for bone density and body composition at the brand new UCSF Imaging Center at Montgomery Street, located in downtown San Francisco, and the UCSF Orthopaedic Institute Imaging Center at Mission Bay. To get a DXA scan at these locations, please see a physician and request a referral.

Additionally, the Body Composition, Exercise Physiology, and Energy Metabolism lab is a partnership with CTSI, Millberry Union Fitness Center, and UCSF Radiology. The lab performs DXA whole body composition exams for self-assessment of body composition without a prescription or referral. This is for individuals starting a weight reduction, strength building, or fitness program who want to monitor their progress with an accurate measure of body composition.

We encouraged those with interest to give us a call or stop by one of our world-renowned locations to see if DXA is right for you!

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