Dexa scans and their value for understanding muscle and fat mass

I’ve mentioned previously how much I like the Dexa scan as a test for body composition.

It gives great insight into several measures that are key players in overall health and disease prevention.

This is a cheap and easy test to have done (the scan itself takes 3mins) and in the future I’m sure there will be more of these small testing sites appearing in cites in the UK other than just London. I’m lucky that we have one just around the corner from my office, so easy for both my patients and me.

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Before I go on, I’d just like to clarify that when I am referring to DEXA scans in this article, I am referring to a DEXA Body Composition Scan. This scan gives a gold standard measure of fat and muscle mass and whilst it does also give a good indication of bone mineral density it is only an indication and not a definitive, diagnosable result. If you are concerned primarily about bone density, then I would recommend that you go for a DEXA Bone Scan – either privately or through your GP.

Back to my scan and it had been 10 years since I had last had a DEXA scan performed so as you can imagine I was keen to see the results now that I am in my mid fifties. Receiving the scan results I was pleasantly surprised and admittedly a little bit chuffed to discover that my body fat has remained the same over the past 10 years and is still very low! This is great news, but boy do I have to work for this on a weekly basis! I was convinced I’d lost fat from my thighs and gained a little across my abs as you would expect as part of normal ageing and the test results confirmed this.

More importantly my VAT (visceral adipose tissue) the fat around my major organs is still very low, reducing my risk for all disease. VAT fat is a key metric when looking at body fat as you may have normal levels of fat overall but high levels of VAT which cannot be measured unless using a test like this. VAT is a source of increased inflammation and activation of the immune system so it’s crucial to keep levels down as it is a major risk factor in cardiovascular disease and cancer. Long term stress and alcohol intake are also big contributors of increased VAT levels. The scan also gives a picture of where fat is stored. I’m pear shaped rather than apple for both fat storage and muscle storage which is much better for disease risk. More fat below the waist is less dangerous than more fat above.

I’ve lost 1.3kg of muscle over 10 years and whilst I’m a little disappointed with this given the amount of time in the gym I’m not surprised. I believe I know the reason why. In 2021 whilst we were still amid Covid I decided that I would try some intermittent fasting given how popular and topical it was in the social and scientific circles. I found it quite easy (especially if I was busy) to restrict myself to two meals per day with my first meal being at lunchtime. I performed this regime for over 6 months after which point I stopped . I was pleased with how super lean I had become but I could also tell I had lost muscle mass. Now I’m not saying that fasting isn’t a good thing to do, it is! But and this is a big but, when you do one positive thing for your health it may also have negative consequences. In other words, I was fasting to improve longevity but in the process I lost muscle mass which may then decrease longevity.  

I haven’t managed to regain the lost muscle mass and in order to do this I would need to be in a calorie surplus on a daily basis. This also presents a dilemma as by doing this I may end up also gaining more fat. 

Whilst muscle mass is a key indicator of longevity, what you do with it is even more important. Hence measures of strength and power become so critical. Luckily my big lifts are still up where I was ten years ago demonstrating that I have been able to maintain the functionality of that muscle. I spend about 3 hrs a week in the gym lifting weights plus an additional  3 hours of Cardiovascular work. I also perform frequent exercise snacks which you can find on my Instagram.

I’m thrilled to see that my bone mineral density (BMD) has gone up by 3% over 10 years. When I first did the test in 2015, I was surprised to see that my BMD was borderline low. And whilst genetically I am a smallish build and have slim bones as a person, I have significantly loaded these bones right throughout my lifetime, so these results were a surprise. 

However, in 2020/2021 the possible reason for this started to play out. I was in the garden every day during lockdown and at the end of a wonderful summer, I had a great tan. A month later I was able to run some bloods that revealed that my Vitamin D level was modest at best. It didn’t make sense based on the amount of sun exposure I had had. I then turned to some genetic testing to get a better understanding of my Vitamin D metabolism (including absorption, transport and receptor acceptance). The results revealed that I had strong gene variations on all these aspects of vitamin D metabolism and that I, as an individual, may need vitamin D supplementation for most of the year to keep levels up to what would be considered normal/optimal. I have since been doing this and testing my blood levels of Vitamin D twice a year to make sure that my dosing and optimal levels are achieved. Given that my bone loading from exercise has not changed I believe that throughout my life I have possibly never had optimal Vitamin D levels (based on these gene results) and no matter how much sun I get I may always need to supplement. I believe this supplemental vitamin D has been a key player in this very positive change in my BMD at a time in my life when you would expect it to be moving the other way.

So, to summarise, the DEXA Body Composition Scan is, in my opinion, an excellent and invaluable test which provides a lot of important data that can be used in the present but also as a measure over time. The only downside as I alluded to is finding a testing centre near to you but hopefully this will change in the not-too-distant future.