DEXA (body composition measurement)

What is a DEXA used for?

Dual Energy X-ray Absorptiometry (DEXA) is a medical imaging device that examines a person’s body composition. It can be useful for people looking to improve their muscle mass, fat tissue and bone mineral density. DEXA is the GOLD STANDARD for measuring a person’s body composition. A DEXA test will assess body composition and it can play a role in reducing medical conditions.

Body fat measurement

Fat mass and fat mass index

Fat mass index is your total fat mass divided by your height squared. This is a better indicator than body mass index since it measures absolute amount of fat in the body in comparison to height.

Total body fat %

This is the percentage of fat that is contained within your body. To improve this percentage, you can either reduce fat, increase muscle or both. A higher body fat percentage can indicate lowered cardiometabolic health. It can be a risk factor for diabetes, insulin resistance, certain cancers and cardiovascular disease.

Distribution of fat

DEXA will measure the distribution of fat in the body. Higher visceral fat poses the highest risk associated with cardiometabolic conditions including ischaemic heart disease, arterial hypertension, type 2 diabetes, and certain types of cancers. This type of fat is the fat that surrounds the organs.

Bone mineral density

The DEXA will provide you with a T score and a Z score to measure your bone mineral density.

The T score compares your bone mineral density to a healthy young adult. The Z score compares your bone mineral density to people of your age and gender.

Measuring T score and Z score is of more importance to the older population as it can assess their risk of osteoporosis. A normal age-related change is loss of bone mineral density, and it is important to measure the decline in bone mass. It can indicate to the elderly what type of medical or lifestyle changes need to be done to address their needs.

Lean muscle mass

A DEXA will measure the amount of muscle in your body. This is important to measure as it can highlight to an individual the amount of muscle they have in their body. It can indicate if muscle mass needs to be increased. High muscle mass is linked with higher resting metabolic rate, improved strength, greater force application in field sports, reduced risk of falls and reduction in all-cause mortality. The DEXA can also show regional muscle mass.

Regional muscle mass

Regional muscle mass refers to the amount of skeletal muscle tissue in specific areas of the body, such as the lower limbs, upper limbs, trunk, or extremities.

This will provide insight into muscle mass distribution in the body which can be important for certain athletes returning to their sport after injury time-off. It can provide valuable information to coaches and training staff in providing an exercise program that is tailored to the weaknesses of the athlete.

Why not just use a scale to measure body composition?

A scale only provides people with their body weight. A person can also work out their BMI if they were to put their weight into this equation: Weight/(height)². A person’s body weight gives us an idea of how heavy a person might be, but it doesn’t provide information regarding the breakdown of their body composition.

This is the drawback of using BMI as the only indicator of health. There can be elite athletes that play rugby union who might be in the “overweight” category of health when using BMI. However, majority of their weight might be attributed to total muscle mass and bone mass. This is why DEXA can be useful here in showing us where is the distribution of total weight.

Thus, DEXA tests can help predict some medical conditions through the assessment of body composition.

What are the contraindications to using a DEXA?

There are very little contraindications to using a DEXA. While DEXA is generally safe, the risk of radiation exposure to the fetus is higher, so it’s not recommended for pregnant individuals. Please confirm with the practitioner on whether you are pregnant or not before undertaking a DEXA scan.

What to do with my DEXA results?

Once you have received your DEXA results, you can start to create a little plan with your health practitioner. The direction in which you choose to take is related to your health goals and lifestyle factors.

Weight loss

If losing weight is important to you, the DEXA results will show you what your resting metabolic rate is (this is important when calorie tracking) and what your fat distribution is. It also shows the amount of visceral fat and what it might mean in relation to chronic disease. Chronic disease is on the rise in Australia which is another reason to support the idea of fat tissue reduction in the medical field.

Muscle mass building

The DEXA scan can also determine where the muscle distribution is in the body and what percentage is lean muscle. If building muscle is important to your health goals, the DEXA result can show you where you lack muscle mass. It can then inform exercise prescription and programming to align with your fitness goals.

Frequently Asked Questions (FAQs)

Why is DEXA considered the “Gold Standard” in body composition?

DEXA directly measures bone mineral content, fat mass, and lean mass, using low-dose X-rays. It provides a detailed analysis of the tissues exact location and distribution. Dexa not only assesses subcutaneous fat (under the skin above the muscle) but also visceral adipose tissue (internal), flagging individuals at a higher risk of type 2 diabetes, other metabolic diseases and osteoporosis. With validation through repeated scientific studies, it provides the most reliable results for comparing results over time compared to other methods of body composition measurements. The “margin of error” is 1% whereas bioelectrical impedance scales range from 5-8% margin and generally overestimate muscle and can underestimate body fat, as well as being more prone to daily fluctuations.

Is the scan safe?

The radiation levels are extremely low. The X-ray machine emits a radiation dose of <0.1 uSv. This is less than 1/80th of the natural background radiation you would receive in a day (from sunlight exposure, soil, etc.) which is around 8 uSv.

What should I wear to my scan?

Wear comfortable loose-fitting clothing, which remains on for the scan. You will be asked to remove your shoes, any metal objects such as belts and jewellery. Avoid wearing an underwire bra if relevant. While the scan is not magnetic, it will show up on the scan results

How often should I have a DEXA scan?

We recommend a scan every 2-3 months.

I am or may be pregnant, can I have a scan?

If there is a possibility that you are pregnant, we will not be able to complete the DEXA scan. As there are no clinical studies to assess the risk to the fetus, we can not 100% guarantee that it is clinically necessary and therefore will not complete the test.

Can I claim the DEXA scan through my health insurance?

You can check whether you are eligible by contacting your health fund.

Can I claim the DEXA scan through Medicare?

Medicare does not offer rebates for this scan.

How long does a scan take?

The machine scan time for a DEXA is approximately 6-7 minutes, although the initial appointment can take 30-40 minutes; as we also provide a consultation, reviewing and interpreting the results, so you can understand what they mean, then support you with an action plan. Subsequent consults generally take 20 mins.

Call to book your DEXA in now