DEXA scanning should be a key part of your ongoing assessment

In this piece we interview Jarrod about having a DEXA scan, the benefits and issues. We’ve structured it as a question and answer session (Q & A).

Tell us about DEXA. What does DEXA stand for?

DEXA stands for dual energy X-ray absorptiometry. A DEXA scan uses two different X-ray energies, one measures the soft tissue and one measures the hard tissue or bone tissue. DEXA differentiates soft tissue into muscle tissue and fat by the different densities of the respective tissue.

Does DEXA expose clients to radiation?

DEXA does emit radiation but it’s the lowest on the scale of radiation emitting medical equipment.  An international flight exposes you to the equivalent dose of radiation you receive from a chest x–ray, which is around 40 to 50 microsieverts.  A DEXA examination only exposes you to around 1 to 4 microsieverts.  Background radiation we all receive each day is 8 microsieverts per day.

How often should someone have a DEXA scan?

Approximately every 12 weeks, depending upon their health goal. Once someone reaches their goal, a six month checkup is usually good. Healthy people may only need a DEXA scan once a year.

How important is DEXA for assessing overall health? Is it especially important as we get older?

DEXA scan reveals important information about the health of your muscular and skeletal systems. A scan tells you if your bones are strong, if you have enough lean muscle mass and identifies areas for improvement. A DEXA scan can let you know if you are at risk for osteoporosis or osteopenia due to thinning bones; it can also reveal signs of muscle atrophy in certain areas of your body. Finally, a DEXA scan can tell you if your body fat percentage is too high.

People tend to lose bone density and muscle as they age, so a DEXA scan can be particularly helpful for monitoring these issues and catching any problems before they become serious issues.  A scan can alert you to significant drops in muscle mass that indicate a problem, and from there you can remedy the situation. It is also important to consider that loss of muscle as you age leads to a loss of functional strength and impacts your metabolic rate.

Can you explain further why monitoring muscle mass is important?

Your lean tissue mass is a large component of your resting metabolic rate, or your basal metabolism.  If you decrease, your muscle mass you are going to decrease your metabolism.  If you do not decrease your food intake in line with your declining lean tissue mass, you are going to start getting fatter.

What is a healthy body composition? What percentage is a marker of good health?

A body fat percentage is the best way to measure health in terms of body fat versus lean tissue.  Females up to 40 years of age should be between 21 and 33 percent for good health.  Males of that age can be between eight and 20 percent.  Females over 40 years of age have an ideal body fat percentage range of 23 to 34 percent. The ideal percentage for males over 40 is 11 to 21 percent.

What about BMI? Is that a good marker for health?

Body fat percentage is preferable to BMI. A BMI score does not account for lean tissue mass, which makes it particularly bad for use with older adults and athletes.

You said DEXA reveals bone density as well. What is a healthy bone density?

Anywhere around 1 g/cm2, but again it depends on age and gender.  I like to just use a universal number of 1. If you know you’ve got a bone density is 1 to 1.2, you know you’re bones are pretty healthy.  The fracture threshold is believed to be lover than 0.85, so if you’re bone health is below 0.85, it’s generally perceived that it is going to be on the lower side. This could indicate osteopenia, which is the precursor to osteoporosis.

So what should a person, especially an elderly person, do if their bone density is low or they have an unhealthy body fat percentage?

This is where a DEXA scan is really helpful. Most people tell older adults to focus on building lean tissue. That is fine if they have low lean tissue to begin with. But a scan may show that a person’s lean tissue mass is fine so instead of trying to increase muscle size, he or she is better off increasing their strength. There is a big difference between training for increasing muscle size and training for improving  your muscle strength.

Last Reviewed 01/Mar/2014

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Dr Meerkin is an accredited Exercise Physiologist and an expert in DEXA technology. He has had extensive experience in sports science research and obesity.

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