A DXA scan, or dual-energy X-ray absorptiometry, is a medical imaging tool used to assess body composition and bone-related measurements. Compared with methods like bioelectrical impedance, skinfold calipers, circumference measurements, or handheld body fat scanners, DXA provides a more detailed and region-specific picture of the body.

It is important to distinguish between two common uses of DXA. The DXA used at your doctor’s office is often performed at specific sites such as the hip or spine to help diagnose osteopenia or osteoporosis. The full-body DXA you take through a direct-to-consumer company is a little different. It is usually used to assess body composition, including fat mass, lean mass, and bone data across the whole body. This article is mainly focused on the full-body version.

As Dr. Steven B. Heymsfield has noted, body composition assessment helps clinicians and practitioners move beyond body weight alone and better understand what is actually changing in the body. That is one of the biggest strengths of DXA.

What Can a DXA Help You Learn?

1.   Body fat. DXA can estimate total body fat and body fat percentage, which gives more context than scale weight or BMI alone. See my previous article on how fast you can lose fat mass.
2.   Visceral adipose tissue. DXA can estimate abdominal fat around internal organs, which is more strongly associated with cardiometabolic risk.
3.   Lean mass. Although it is often labeled “Lean Mass” on a DXA scan report, it technically should be called “lean soft tissue.”  This is because bone mass is lean, but not soft, and so does not fall into this category on DXA. Lean soft tissue includes muscle, organs, connective tissue, glycogen, residual food mass in the gut, and water. It is useful, but it is not the same thing as pure muscle mass.
4.   Bone mass and bone density. A full-body DXA provides bone-related information that can still be useful, even though it is not the same as a site-specific diagnostic osteoporosis scan. Generally, it will tell you the pounds/kilos of bone in the body, and an overview of bone mineral density, although not with diagnostic precision.
5.   Regional body composition. DXA can show how fat and lean mass are distributed across the arms, legs, and trunk. This is especially useful when trending lean soft tissue alongside your exercise metrics.
6.   Left-right asymmetries. It can reveal meaningful differences between sides of the body. Although it is normal for most folks to have some small difference, a large difference could be something worth addressing.
7.   Progress over time. Repeated scans can help determine whether changes in body weight reflect fat loss, lean mass change, or both. That being said, it is generally advisable to avoid taking DXA too frequently, to avoid getting noisy data from error and condition-specific changes, and to avoid radiation (however small – see below).
8.   Context for nutrition and training decisions. DXA can help guide expectations, calorie targets, protein goals, and training priorities.

Who Might Want a DXA?

A DXA may be useful for people pursuing fat loss, muscle gain, athletic performance, healthy aging, or a more objective understanding of their body composition. It can be especially helpful for people frustrated by the scale, since body weight alone often hides what is really happening. DXA can also offer helpful clinical insights, and many times is the first indication to someone that they need to address their health.

Who Should Not Get a DXA?

Pregnant women should generally avoid DXA because radiation exposure is typically avoided during pregnancy, even when the dose is low.

Radiation Dose in Perspective

One common concern is radiation. That concern is understandable, but the good news is that the effective dose from a full-body DXA scan is very low—about 4–5 microsieverts on newer systems. For perspective, that is 0.004–0.005 millisieverts (mSv), which is well below the public dose limit of 1 mSv per year from non-medical, planned radiation exposure and far below the occupational limit of 20 mSv per year averaged over 5 years for radiation workers. It is also lower than the average amount of natural background radiation a person receives in a single day, which has been estimated at about 6.7 microsieverts per day. Research and professional guidance therefore consider DXA radiation exposure to be minimal for most non-pregnant adults when used appropriately.

How We Use DXA

At Redesign Nutrition, DXAs help us move beyond guesswork. They allow us to better interpret progress, understand whether weight change reflects fat or lean tissue, and personalize recommendations with more precision.

Be sure to catch my upcoming article, “How to Read My DXA Scan.”

All the best,

Kevin Rogers, RDN, LD

Founder | Redesign Nutrition

References

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International Commission on Radiological Protection. (2007). The 2007 recommendations of the International Commission on Radiological Protection (ICRP Publication 103). Annals of the ICRP, 37(2-4), 1-332.

Kaul, S., Rothney, M. P., Peters, D. M., Wacker, W. K., Davis, C. E., Shapiro, M. D., & Ergun, D. L. (2012). Dual-energy X-ray absorptiometry for quantification of visceral fat. Obesity, 20(6), 1313-1318.

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Nana, A., Slater, G. J., Hopkins, W. G., & Burke, L. M. (2015). Effects of daily activities on dual-energy X-ray absorptiometry measurements and implications for measuring body composition in active populations. Sports Medicine, 45(2), 271-282.

Shepherd, J. A., Ng, B. K., Sommer, M. J., & Heymsfield, S. B. (2017). Body composition by DXA. Bone, 104, 101-105.

U.S. Nuclear Regulatory Commission. (n.d.). Occupational dose limits for adults. https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1201.html

United Nations Scientific Committee on the Effects of Atomic Radiation. (2008). Sources and effects of ionizing radiation: UNSCEAR 2008 report to the General Assembly, with scientific annexes. Volume I: Sources. United Nations.