What is DEXA?
The DEXA scan is the gold standard of body composition measurements. It allows you to see exactly how much fat and how much muscle you have. It will tell you where that muscle and fact is, point to associated risks or hormonal issues, or identify muscular imbalances.
For a more detailed look at what DEXA is, and how it can assist you with your health and fitness programme, take a look at this video, produced by Hologic, the manufacturer of the DEXA machines we use.
How does it work?
The scanner passes a small amount of two different X-ray beams through the body. The rays are absorbed or pass through the body in known quantities. Different amount of the first beam will be absobed by fat and by muscle, and the second beam will be absorbed by the skeleton. By measuring the amount of each beam which makes it through to the sensor on the other side, we are able to tell how much fat and muscle and bone there is in that part of the body.
X-rays? Is it Safe?
The amount of radiation you are exposed to in a DEXA is tiny. It is roughly equivalent to about a day’s worth of background radiation from just living, or about the safe as the additional radiation you get from taking a flight from London to Paris. Our DEXA machines are regularly checked and calibrated to ensure that this remains the case. There is absolutely nothing to fear from taking a DEXA scan. We also limit the number of scans a person can take in a year to 6, with individual scans being taken no less than 6 weeks apart.
What’s the procedure?
You will be asked to undress to underwear and remove all jewellery/watches. A hospital gown can be provided if needed. Bras with underwires will also need to be removed. The Dexa technician will position you lying face-up on the bed, ensuring that you are evenly spaced. They will also lightly secure your feet to each other so your legs can’t swing. When the scan is operating the receiver arm will pass over your body in three sweeps, and will gradually build up a picture of you. It is important that you are very still while the scan is happening to ensure the best quality image. Once the scan is over the technician will tell you it’s ok to get up, and dress once again. You’ll be on the table for approximately 4 minutes.
What do you get?
After the scan, the technician will print off a multi-page report, and will walk you through some of the key points. Your trainer can advise you on how best to take advantage of the information given to work into your training and nutrition plan.
What about alternatives?
DEXA is the Gold Standard in body composition analysis. No other method comes close for its consistency, ease of application and specificity. DEXA is also the only measurement which will give you accurate fat mass, fat-free mass and bone mass, not just overall, but in each part of the body. This means that it can double as a measure of how recovery from injury is going, or detect imbalances between the left and right side. It is also the only measurement which can give an indication of visceral fat – this is the fat which sits around the organs. This type of fat is appearing regularly in recent research as being an indicator for a range of health conditions.
Below is an analysis of some of the other methods out there.
This is the most commonly used measure in the medical profession. It’s a simple height and weight calculation. In anybody who has never seen the inside of a gym this might be ok. But once you’ve ever lifted up something heavy, it will cease to be relevant.
BIA / Bioimpedance
This method, most commonly found on gym floors or even in people’s bathroom scales, passes a small current through your body. It is predicated on the idea that muscle and fat will concur that electrical current at different rates. Among the problems found is levels of hydration and numerous other factors also influence this. The machines have consistently failed to produce reliable or meaningful composition results. They are not used in any research on body composition.