DXA - Body Composition and 6 Reasons Why You Might Want One

Dual X-ray Absorptiometry - DXA is the Gold Standard for body composition.  The technology uses two x-ray beams of differing energy levels to scan a person’s whole body.   The difference in the absorption of the two beams by the three major body compartments: bone mass, lean muscle and fat provides the data that allows for a computer to determine a person’s:

• body fat
• abdominal/visceral
• lean muscle mass
• bone density

So why is this important?
Modern lifestyle, with too much food (of questionable quality) and too little exercise leads to some inevitable consequences.  Body fat increases, lean muscle mass decreases and bone density decreases.  From a physiological perspective, there is nothing inherently wrong here - this is actually how the body was designed:  

• when we eat excess calories we are designed to store them for a day when calories are not to be found - unfortunately, evolution did not design us to eat excess calories every day, so if we do that, we get fat.
• when we are active - walking, running, climbing, lifting, pushing, digging; our body sends signals to increase the strength of our bones and muscles.   This too makes sense, it allows an individual's body to optimize for their activities - again, evolution did not contemplate that many of us would do little to no activity.

Most often these changes are recognized when a person becomes overweight and we use their Body Mass Index (BMI) - an index that attempts to define the amount of tissue per standardized unit of height - it does this simply by dividing the height by the weight squared and is measured in kg/m2.   But BMI does not differentiate between bone, muscle or fat.  So if you are very strong with large muscles and large bones on an average or even small frame - your BMI may tell you that you are overweight.  Commonly accepted BMI ranges are underweight: under 18.5 kg/m2, normal weight: 18.5 to 25, overweight: 25 to 30, obese: over 30.
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More challenging then the strong muscular person who is labelled overweight (most physicians generally recognize this), is the opposite situation: a person with decreased lean muscle, decreased bone density and increased fat where their BMI places them as normal even though from a body fat percentage they are obese.   This is far harder to detect in clinical practice, and is probably more common than most realize.

The second reason to want a DXA - even if, in fact, especially if, you are obese, is to understand the nature of your obesity.  Fat accumulation around the visceral organs in the abdomen is highly associated a destructive self reinforcing cycle of inflammation, insulin resistance, high blood sugars, hypertension, hypercholesterolemia and in turn more adipose fat accumulation.  This viscous cycle, known as metabolic syndrome, is highly associated with diabetes, heart disease and stroke.  

Shockingly, according to a 2011 study almost 1 in 5 (19.1%) of Canadians are estimated to have metabolic syndrome, and most are undiagnosed, (and I suspect things have gotten worse in the last 7years!)

The most common component of metabolic syndrome in Canadians: abdominal obesity.

A low tech approach to estimating abdominal obesity is to measure the waist to hip ratio - anything above 0.9 for men and 0.85 for women is considered by the WHO to signify abdominal obesity.  Less accurate than a DXA and without the lean muscle and bone density information, but a critical metric nonetheless.

Reason #3 - DXA provides hard-to-get-otherwise information
Maintaining lean muscle mass, along with strength and bone density are strongly positive indicators for longevity - or said another way:  loss of muscle mass and bone density are associated with premature death.

Here the challenge for the clinician is greater than with abdominal obesity.  Often there is simply no way to know a patients lean muscle mass and bone density without DXA measurement.

Reason #4 - this is the best part
So we now know that DXA gives us some really good information, but the best part is that all of the important markers for vital longevity it tracks

1. Body Fat
2. Abdominal or Visceral Fat
3. Lean Muscle Mass
4. Bone Density

All of these, are highly modifiable by lifestyle intervention.  In fact one of the most satisfying  aspects of using DXA scans in Lifestyle Medicine is showing patients their early progress, 3-4 months in when the scale has hardly budged.  All too often, we see patients with total weight loss of <5 lbs. who come in frustrated and feeling defeated only to learn that their DXA shows a significant body recomposition (Net loss 5 lbs: lean muscle gain: 5 lbs and bone mass gain: 1 lb; Fat loss: 11lbs).   What is most interesting is the tyranny of the weight scale - these same patients know that their clothes fit differently that they have decreased sizes, yet the absolute number on the scale is what often bothers them the most.  For these people having the DXA results is a major reinforcement of the power of their lifestyle changes. 
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Reason #5 - DXA scans are very safe and can be repeated multiple times in a year.
But don’t they use x-ray radiation?

• True, but the radiation received by the patient during the scan is less than that of an airline flight from Victoria to Montreal and back. (Reference)

Reason #6 - DXA scans are relatively inexpensive 
DXA for total body composition is not an insured service, so cost will be an issue for some.
However, given the nature of the test and the data they produce for many DXA's are a cost effective investment in their health. ($120 for the first test; $100 for follow-up scans.)

In summary - 6 Reasons Why DXA Scans are so useful 

1. weight and BMI are misleading - they don't tell the whole story
2. understanding to the degree which you have abdominal obesity is vital for metabolic health
3. DXA measures lean muscle mass and bone density which are important for vital longevity and really hard to estimate clinically
4. all the key metrics from the DXA are modifiable by lifestyle intervention
5. the test is very safe
6. the test are relatively inexpensive

At Wellness Garage, we are proud to announce that Bodycomp Imaging is locating a DXA scan within our facility that will be available for our clients as part of our assessments.
We are very excited to see this technology come to the South Surrey/White Rock area.   Clients are free to book with Wellness Garage or Bodycomp at their convenience.

* Wellness Garage and Bodycomp are independent businesses - and Wellness Garage derives no profit from DXA scans done at our facility.