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If you’re a PT, how do you prove (for certain) that you’re making a difference?

If you’re a personal trainer, S&C coach or nutritionist your success rests squarely on your clients’ tangible results. And if you’re any good at what you do that should primarily mean reducing their body fat and/or increasing their lean muscle mass – both in absolute terms and as percentages of total body mass.

The accuracy with which you measure those changes therefore reflects how truly successful you really are. If your clients don’t have faith in the way you measure their body composition that will reflect badly on you. If they don’t believe the results, they won’t believe in you.

Unfortunately, the most accessible, lowest cost and therefore popular methods of measuring body composition are also the most unreliable and imprecise.

At the very back of the pack are plain old bathroom weighing scales (and their fraudulent offshoot, body mass index). Scales tell you nothing more than your relationship with gravity, so unless your client is a jockey or a boxer who needs to compete in a weight class, scales should play no part in your armory.

Skinfold calipers are cheap, prevalent and have their place in measuring body changes but, like a gun, in untrained hands they can be dangerous. In Sports Nutrition for Paralympic Athletes (2014), editor Elizabeth Broad quotes studies that state, “…highly skilled technicians are required if reliable data are to be collected. Technicians need to be meticulous in terms of both accurate site location and measurement technique. Measurements just 1-2cm away from a defined site can produce significant differences in results…”

In an article in Cyclist magazine (2015), British Cycling coach Andy Kirkland more bluntly reinforces the need for caliper practitioners to be highly qualified: “Unless you’re a skilled practitioner, for example ISAK certified [International Society for the Advancement of Kinanthropometry], skinfold analysis – using calipers to measure the thickness of fat at certain sites around the body – can be next to useless.”

Another technique for measuring body fat is bio-electrical impedance analysis (BIA), whose form factors range from £50 scales you can buy in a department store to £13,000 devices that resemble airline self-check-in kiosks.  

Whatever the cost, the technology (which actually measures electrical resistance to make a guess about body water to, in turn, make a guess about fat) is the same. The variation in price range is only matched by the variability of the results – drink a litre of water and the device will record lower body fat. Or if you’re not thirsty, simply flick the switch on many BIA devices to the ‘athlete’ setting and your fat reading will miraculously drop. Lean at the flick of a switch! Tempting but hardly scientific.

The most accurate way of measuring body composition and now universally regarded as the gold standard is dual-energy X-ray absorptiometry, or DEXA.

As the name suggests, DEXA produces X-ray photons of two different energy levels. Bone and soft tissue slow down the X-rays at different rates, so the composition of bone, fat and lean mass can be separately and precisely analysed.

That’s why DEXA is favoured by the country’s leading sports science universities, such as Bath and Exeter, and professional teams like Chelsea, Arsenal and West Ham football clubs, and England Rugby.

As well as accuracy, DEXA automatically provides regional data and imagery for arms, legs and trunk in order to get an accurate picture of fat and muscle distribution (been skipping leg day, bro?) It also gives a very good estimate of visceral fat, which is the ‘bad’ fat that surrounds the internal organs and is linked to heart disease, diabetes, stroke and even cancer.

As you’ve probably guessed by now, you can’t buy a DEXA scanner in John Lewis. DEXA is an expensive piece of medical-grade equipment that your clients have to travel to and that will cost them £100 or more.

But the accuracy, precision, depth and breadth of body composition data makes it essential for baseline and quarter-to-half-yearly measurement. In Australia, Canada and the US, where DEXA is well established, it’s common practice for PTs to insist on a DEXA scan before signing up a new client.

If you’re a personal trainer DEXA gives you research-quality, high-calibre information that adds to your credibility, motivates your clients and differentiates you in what is undeniably an overcrowded industry.

A mediocre PT will fear DEXA because it doesn’t discriminate. Unlike calipers and BIA, you can’t squeeze harder or flick the ‘athlete’ switch to fudge the result.  

On the other hand, if you’re a PT who values accuracy, veracity and professionalism you will embrace DEXA because it will prove beyond doubt that you’re making a difference. Your clients will stay motivated and keep coming back for more.

Bodyscan ( is the UK’s only company dedicated to DEXA body composition measurement and has two sites in central London. Clients book online, receive an immediate printed report and can opt for an in-depth consultation that brings the report alive with a highly personalised analysis.

Bodyscan’s customer reviews are 95% five-star, so your clients are in very safe hands and will thank you for the introduction.

We recently had a TV crew in to film some people who were committing to lose a lot of weight (ie, fat).

One of them, Julie, has a huge task ahead of her because she is carrying as much fat as my total weight (68.9kg). See part of her report below.

At Bodyscan, while we don’t focus too much on body fat percentage (preferring fat mass index), Julie would be in a far better place at around 26.5% body fat, which means she should lose about 35kg of fat from her total weight of 127kg.

Just a few minutes struggling with the barbells in my local gym yesterday (above) made it easy to know what it would feel like to be 35kg heavier (and then 35kg lighter once I’d managed to put the barbell back in the rack). It was hard work. It also made it obvious why very overweight people have super-high muscle mass – they’re doing a very strenuous workout with every step they take.

If you’re overweight, work out how much fat would be good for you to lose: women take 26.5% of your weight, men 18% of your weight, in order to arrive at a better fat mass. Then see how much higher than your current total fat mass it is. That difference is how much fat you could aim to lose. Now go and pick up that weight in the gym to get a sense of how much better you’d feel without that ballast.

If you’re below those body fat percentages you’re doing well.