Body fat testing is a popular way to gauge the effectiveness of your exercise and nutrition program. While once relegated to hospitals for medical and research purposes, DEXA (DXA) scan body fat testing is now available to the general public -with no prescription required. I believe this is a mistake and I DO NOT recommend the general public get DEXA scans to measure body composition. These devices are now showing up in wellness / anti-aging clinics and private medical offices. Some gyms may have them too. I believe testing body fat with this device is a grave mistake whose ramifications may not be recognized for years to come.
What Is DEXA?
DEXA – also called DXA – stands for Dual-Energy X-ray Absorptiometry. It uses low-level x-ray radiation. Anyone who had a bone density scan to test for osteoporosis or osteopenia has probably had this test performed.
In addition to testing the strength of your bones, the DEXA scan can also measure your:
- body fat percentage
- muscle density
DEXA is often called the body fat gold standard, by which all other tests are compared against.
This scan is more accurate than:
- 3-D Body Scanning
- Bod Pod (Air displacement plethysmography)
- BIA (bioelectric impedance analysis)
- Near–infrared interactance (NIR)
- Body Mass Index
- Skin fold analysis
- Circumference measurements
It's even more accurate than underwater weighing (hydrostatic weighing).
DEXA Scans And Personal Trainers
It's possible DEXA scan companies may reach out to fitness trainers help market this device to the public.
I was first alerted to this by my friend and colleague Jessica Lewis, who told me how she was approached by a company to recommend DEXA body fat testing to her clients.
Unfortunately, the fitness industry -which has a chronic case of shiny object syndrome – has not addressed this topic.
Even some universities now promote DXA to the general public.
One pro-DXA website says personal trainers can use this body fat data with clients so they can:
- Find muscle imbalances. Prevent injury by locating weaknesses early
- Optimize exercise training. Making sure workouts are not too challenging or too easy.
The prestigious UC Berkeley website makes these statements about DXA:
- …it is a scan that can be used for anyone.
- …the average person who is simply curious about their health could get this scan in order to gain insight regarding their body composition.
Exercise physiologist Bill Sukala has told me of non-medical related DEXA scan businesses in Australia which offered Groupon discounts. Some US businesses offer Groupon discounts too.
Before recommending these scans to their clients, fitness pros should remember, “first do no harm.” This device exposes your clients to unnecessary radiation. While it's a low dose, you don't know what this exposure will do to them years later.
See my Instagram page for more on this discussion.
How Often Should You Get The Test?
Some websites say every 3-6 months. That's 2-4 times per year!
Where is this number coming from?
Who made it up?
According to the International Atomic Energy Agency (IAEA), there is no upper limit on the number of DXA scans someone can do – provided those scans are “medically justified.” That's the key – medically justified.
When a physician prescribes the scan, it's to help diagnose a medical problem. Doctors are not sending people to get their body fat tested several times a year just because they are curious.
The IAEA says that while the amount of radiation used is low, “The risk increases with the number of scans.” Obviously, in a medical situation, doctors will weigh risks vs. benefits.
Who is weighing risks vs. benefits when you get your body fat tested 2-4 times a year?
Who Operates The DEXA Machine?
If you get this test done, you should ask about the operator's qualifications.
According to a 2006 Technical White Paper on Bone Densitometry, by the Conference of Radiation Control Program Directors (CRCPD.org), even an “office clerk” may operate DEXA machines.
If you are doing the body fat analysis test, a fitness trainer may be the operator.
While a certification should be obtained prior to operating, the White Paper stated 16 states in the US did not have central body DEXA certifications.
It's further stated some may not be aware their state has training requirements for DEXA operators.
What about the calibration of the equipment? X-ray machines (C-arms, as they are called) need to be regularly inspected by a radiologist to ensure they are providing the proper dosage. Who regularly calibrates the DXA machines being used in wellness centers etc?
This is a question you should ask.
Granted, this White Paper is several years old. Hopefully, someone from the Department of Energy or the American Registry of Radiologic Technologists (AARTR) will read this and leave a comment below.
The Dose Makes The Poison
The DEXA scan uses X-ray radiation to determine body composition. We know radiation causes DNA damage and can cause cancer by promoting the formation of free radicals.
Proponents of DXA body fat testing often say the machine uses very low radiation levels. While true, this low level is added to all the other low-level radiation sources you are exposed to.
Basically, the dose makes the poison.
Think about it: you are exposed to x-ray radiation when you:
- get dental x-rays
- go through an airport TSA checkpoint
- get an x-ray or CT scan at the hospital
Now, some people are saying it's OK to get this scan 2 to 4 times a year?
What happens to you when you add up all these low-dose exposures – and repeat this for years?
But, It's Low-Level Radiation
The big argument for DEXA being safe is it uses very low amounts of X-rays. According to the Health Physics Society, a whole-body DXA produces about 0.04 milli-rems of radiation.
For comparison, a dental X-ray exposes you to about 2 milli-rems.
I will reiterate. Radiation adds up. The more you are exposed, the greater the potential side effects. This is why X-ray technologists and other medical professionals wear dosimeters to tell them how much radiation they've been exposed to.
One person made the argument to me that the radiation you receive is about equal to what you'd get if flying from New York To California. So, if this is really is a low level, why do studies show airline pilots and flight attendances have greater rates of cancer?
Could it be because all those low-level dosages add up over time?
How Low Is No Risk?
One investigation attempted to answer the question of how risky low-dose radiation was. To quote the researchers, “we cannot be sure of the appropriate dose–response relation to use for risk estimation at very low doses. “
Basically they said, when it comes to low dose radiation, we don't know which dosage will lead to the lowest risk. Obviously, the less you radiation you receive the better – which is my argument.
When I spoke to x-ray technologist Tim DiFelice, owner of PMX Services, an x ray company, he said people might have different susceptibilities to x-ray radiation. For example, one person may never get thyroid cancer while someone else, getting the same dose, eventually might.
The US Nuclear Regulatory Commission (US NRC) website also states:
“…radiation affects people in different ways.”
To be fair, the USNRC further states
“Low doses spread out over a long period would not cause an immediate problem” but they also say, “The effects of doses less than 10,000 mrem over many years, if any, would occur at the cell level. Such changes may not be seen for many years or even decades after exposure.”
Tim DiFelice, went on to say “why would someone who eats well and exercises to stay healthy want to expose themselves to something which might harm them in the future?
Who Should Not Get DXA Scans
As a rule, the following should speak to their physician before undergoing this body fat test:
- Pregnant women
- People of childbearing age (both females and males)
- Radiation workers
- Airline pilots /flight attendants (my opinion)
- Frequent airline flyers (my opinion)
The more radiation, the greater your risk is.
The price to buy a machine costs between$20 thousand and $30 thousand dollars. I have even seen DEXA machines to be purchased on Ebay. How is this not regulated?
The issue is companies usually do not require a prescription to perform this body fat scan.
Just pay $80 or so, and you can have this test done.
But, at what point would a company say enough is enough and turn away customers that it thought were over-radiating themselves by getting too many DXA scans?
Obviously, well-meaning organizations would set a limit on the number of scans per year.
But what about those who believe the mantra “it's a low dose, so it's no harm?”
Also, if someone was turned away, what's to stop that person from getting scanned at a different business? I'm thinking specifically about those with eating disorders who are preoccupied with their body fat levels.
Is there a central database that all DXA scan businesses can access so they know how many scans someone has had?
This is a conversation we need to have.
Body Fat Tests I Recommend
What body composition tests do I feel is most appropriate for the general population? Aside from the “mirror test,” I prefer bioeletric impedance analysis (BIA).
Here are the reasons why:
- The devices are affordable
- It doesn't use radiation
- You get results in about 20 seconds
- They are easy to use
Bioelectric impedance is a technology used in most fitness centers too.
Is BIA perfect? No. But most people don't need super accurate body fat testing. By performing the test regularly under the same conditions, you can see changes.
If you want more accurate body fat results, then I recommend:
- Underwater weighing
- Bod Pod
Neither of these uses radiation either. Most universities will have Bod Pods and may even have a dunk tank for underwater weighing. You can get these tests performed on you for about $45.
Should You Get A DEXA Body Fat Test?
In clinical and research settings, DEXA is a powerful diagnostic tool. I can even see how some pro athletes may benefit from testing too. But, for the average person, I believe using radiation to measure your body fat -especially on a regular basis – is a mistake. If you are using DXA to test your body fat, you're a guinea pig.
Don't believe the marketing hype that low radiation means it's totally safe. Airline pilots and flight attendants are regularly exposed to lose dose radiation and have increased cancer risks. Radiation adds up in the body. The more times you're exposed, the greater your risk. So, are DEXA scans used for body fat testing safe? We won't know the answer for many years. The best solution is to avoid this body fat test and opt for a less invasive test like the Bod Pod or bioelectric impedance.
Any Comments or Questions?