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).
Some say Magnetic Resonance Imaging (MRI) is the most accurate, but it's unlikely people in a health and wellness setting would have access to an MRI machine.
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
I like models from Tanitia and Fit Bit.
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?
Thank you for that information. I was considering DEXA test by one of the local fitness outfits, but after reading your opinion and also because my primary concern is bone density and the accurate state of it, I am not so sure it would be an appropriate way to go. Do you have any recommendation as to the most accurate (and least radioactive) bone density scan/testing?
Hi Nonna, while I like DEXA when used in clinical settings (hospital, prescribed by a doctor), Im not a fan of DEXA used in fitness centers. That’s because I don’t know who operates the machines (X ray tech or personal trainer etc) and I dont know how the equipment is maintained or what dosage of X rays you are getting – and how that matches up to the dosage you’d get in a DEXA machine in a hospital setting. These would be questions I would ask the fitness center.
While Im not a radiaion expert, for the least radiation I’d suggest getting it done in a hospital. I’d also request for a thyroid shield during the test. Im sure your doctor can recommend hospitals in your area that offer DEXA and can help you determine your bone density
I’m 26 weeks pregnant now!
Actually before my pregnancy was detected i had gone through dexa for the very first time and I realised now that when dexa was performed i was 5 weeks pregnant so will it cause any harm??
Hi Jhanki, congratulations on your pregnancy! Don’t worry about what happened before you knew you were pregnant. What’s done is done. Just limit your future unnecessary radiation exposure going forward.
Did you get your DEXA scan at a fitness center or by a personal trainer? If yes, I’m curious if they asked if you were pregnant? I know you were not aware of your pregnancy when you had the scan performed. Just trying to get an idea of the pre-screening questions they ask people.
Dora Phill says
DNA damage point is so concerning, Dexa has to be in hostipal setting but these things are scary.
Dora, I agree, it’s very scary. Even more so when I think that the average person may not know DEXA uses radiation which may harm them down the road from repeated unnecessary scans
I own the FIT 3 D SCAN for my studio. Is this safe or no?
Michelle, I looked the Fit 3D scanner up. To me it looks like the Fit 3D Scan uses a special camera to take pictures and measurements. It does NOT use X rays like a DEXA scan, so you are OK. 🙂
The Fit 3D scan reminds me of the Shape Scale which I reviewed previously. Take a look.
I knew DEXA could calculate body composition from a scanning I had for bone density when the x-ray tech gave me my fat and muscle percentage as an added bonus, but never in my wildest dreams did I think that it was being performed outside a hospital or radiology center. I can’t imagine anyone paying that kind of money for DEXA machine, not to mention having someone like that in the hands of someone who is not a healthcare provider.
Judy, I agree, this thing has no place in the general public. Like you I thought DEXA was only found in hospital settings. I was surprised as well when I learned this isnt true anymore. The DEXA industry is reaching out to fitness trainers to market this to clients. Some fitness trainers may even own these machines. There are a lot of pro-dexa articles out there. My fear is fitness trainers who dont understand what this is, to start recommending it. I am getting asked about this in classes now, so I know its getting popular.
During a recent DEXA (for osteoporosis), I asked the tech for my body fat percentage, and she saw it was at 19%, I had BIA done with a handheld device at a health fair, and the trainer said my % was 29, surprising to me since even other recent BIA measurements were less than 19%. I am questioning the accuracy of the BIA device, as I was under the impression DEXA is supposed to be more accurate. How can the two differ so much?
Judy, compared to DEXA, handheld BIA body fat devices are far less accurate. Go with the 19% DEXA said you were at (which is fantastic by the way!). bioelectric impedance (BIA) might overestimate or underestimate body fat depending on several factors. General rules when doing BIA is to:
not exercise or drink alcohol for 12-24 before the best
urinate at least 30 minutes before the test
For best results I often suggest doing the test at the same time of the day AND the same date of the month, just to make sure things are as same as possible. But even then, I expect about a 5% to 10% error factor when using BIA.
Sometimes the error can be significant. I rememvber one woman years ago, who started to cry because her body fat was significantly higher after she worked out than before.
The handheld BIA devices are popular at health fairs because they are quick and easy to use and nobody has to take their clothes off to get their body fat tested. THe downside is their accuracy is less than DEXA or underwater weighing.
Thanks Joe. Good to know. I did not drink alcohol but did urinate before. I forgot about that!
I think you are fine Judy 🙂
Is is common to be given fat percentage after a bone density dxa scan? Is it something you request or is automatically just part of the scan itself. I have a bone density test scheduled in April, just because of age.
Calirose, that’s a good question. I’m not sure if a hospital would give you your body fat percentage after you get a bone DEXA scan. I know they can see the fat but whether they do a calculation to determine percent body fat I’m not sure. Ask your doctor and the technologists when you get your DEXA scan and let me know what they say. You ask a good question that I’d like to know too.
Thanks for the reply. I found your article very helpful and I do feel that any unnecessary radiation is a poor idea! You gave me more information than I had previously and solidified my resolve not to DXA just for fat %.
I will see what they say, and let you know. It may be a few months now – the hospitals and facilities in this area are postponing non- emergency or non-urgent tests, scans and such because of flu and possible COVID 19, even though there has been no cases at all of COVID in our area.
Anyway, just curiosity for me, wondering how age has affected me in terms of muscle and fat, as I weigh the same as I have for decades, I do not work out with the same intensity as I used to!
Calirose, glad I was able to help. I can understand why hospitals would be shoring up their resources for the coronavirus. My guess is most healthy people don’t have much to worry about but just in case its good to be prepared.
See if they can tell you your muscle mass as well as percent body fat. Sometiems as we get older we lose muscle and thats called sarcopenia. Muscle mass is more important because of thats a factor in our ability to maintain our daily living activities. A strong person is a healthier person. The DEXA will tell if thats happening. My guess is if your working out regularly, then you may be doing ok in the muscle preservation department.
Hopefully COVID stays out of your area. I’ll look forward to hearing what happens when you get your DXA scan 🙂
Finally I got that DEXA scan for bone density! In my case, they did not do a full-body scan as my Dr. and I felt that at my weight and exercise level we did not need to address the issue of fat or muscle and the least amount of radiation was the best!. I had only a neck, one hip, spine and one ankle scanned. It seems it varies by location, risk factors, and what the patient and Doctor decide so it will be different for others.
Thank you again for all the info.
Carlirose, I’m glad you were able to get your scan and were able to speak with your doctor about it. Risk factors definitely play a role but it sounds like you got enough scans done to get a good idea of what your bone density is. I hope you have been keeping well and have a nice Halloween 🙂