DNA tests not fit for purpose

There is little scientific basis for their use in the fitness industry, but this won’t stop the marketing hype.

Liverpool midfielder Mohamed Salah is one of the Premier League footballers who have used DNA tests to tailor their training. Picture: AFP

If you really can’t shift that excess weight or run a marathon, you can always blame your genes. Science — and a lucrative spin-off industry — has provided us with a convenient excuse for our physical shortfalls in the form of DIY genetic tests.

On sale in the foyers of boutique gyms, online and in your local pharmacy — with names such as FitnessGenes, DNAFit, Pure Genetic Lifestyle and myDNA — they purport to help you “unlock everything you need to know about your wellness” and “eat and exercise in harmony with your DNA”.

Andrew Steele, the head of product and professional sport at DNAFit, the market leader, says his company was among the first handful to enter the market. “Now there are literally hundreds of different products. The level of growth has been phenomenal.”

Doubtless the trend is buoyed by reports that English Premier League footballers such as Liverpool’s Mohamed Salah, and Olympic athletes such as former long jumper Greg Rutherford, have used them to tailor their training and diet plans.

A 2018 report by the medical analyst Kalorama Information (a division of marketresearch.com) predicted that global sales of these DNA kits (excluding those sold for paternity tests) will increase from $140 million in 2017 to $440m by 2022. Pay the fee, send off a saliva sample and you will learn whether you are programmed to overeat or under-respond to exercise and what to do about it.

Who is to argue with what is imprinted in their genes?

Well, some experts do. In 2015, a consensus statement signed by 22 genomics and sports scientists and published in the British Journal of Sports Medicine concluded that home DNA fitness tests “have no role to play in talent identification or the individualised prescription of training to maximise performance”.

And in December a paper published in the journal Nature: Human Behaviour hinted at the possibility that, whatever the kits tell us, our minds are more influential than our DNA when it comes to getting in shape.

According to findings from the research team at Stanford University in California, we can probably override our genotype with our mindset. In other words, if we believe a certain type of exercise is beneficial, then it probably will be, regardless of our genetic make-up.

To reach this conclusion, Alia Crum and her team from Stanford’s department of psychology recruited 200 people and asked them to provide a saliva sample for genotyping. They were then divided into two groups, one completing a treadmill test to exhaustion, the other given a liquid 480-calorie meal. Both groups were asked detailed questions about how they felt after the trials before being asked to return to the Stanford labs.

Once there, researchers told some of the treadmill runners they had a particular gene variant that prevented them from responding to aerobic exercise, although in most cases it wasn’t true. Likewise, some of the diet group were falsely told either that they carried a gene variant that didn’t prompt feelings of satiety and might cause them to consume more calories than they needed, or the opposite — they were genetically programmed to feel full.

When the participants repeated their initial trial, the running group who thought they had a faulty exercise gene were shown to cover less distance and be fatigued more quickly, and the diet group who thought they had the anti-obesity gene reported feeling satiated more quickly after the liquid snack.

Even more surprising were the results obtained when Crum compared the performances of people who really did have adverse gene variants with those who mistakenly thought they did. Although the “real” genes had a small negative impact in the eating and exercise tests, so did the perception that people were harbouring them.

Crum says that in people who wrongly believed they had “genetic risk” the outcomes were sometimes worse than in those who actually had them in their genotype. It comes as no surprise to Colin Moran, a researcher in genetics and physical activity at the University of Stirling, that consumer DNA kits failed to make much of an impression.

“There are many, many examples of these tests not being very accurate,” the professor says. “And my message would be that if people want to pay for them, just do it for a bit of fun.”

I became sceptical about DNA testing kits when, a few years ago, I tried several of them and was sent vastly different results, with some suggesting that running and cycling were my thing, others that I should try weightlifting and strength-based activities.

With an already overwhelming choice of gym classes and fitness challenges, the last thing the average consumer needs is to be left feeling more confused after parting with their cash. Yet it’s an industry that is very much in its infancy, Moran says, and it could be decades before we know enough about the genes influencing health and fitness to even think about making accurate fitness and diet prescriptions.

Very roughly, about half of the differences between us all are down to genetics and the present crop of tests looks at only about eight to 10 of a possible thousand gene variants.

Alun G. Williams, a researcher in sport and exercise genomics at Manchester Metropolitan University, says: “It’s like trying to tell the whole story of a 500-page book, but only being allowed to read three words per page.”

Most experts agree that they don’t really tell us much at all.

“For example, some kits test for a gene variant called ACTN3 that we know accounts for about 2.4 per cent of sprinting speed,” Moran says, “but just because you have that gene doesn’t mean you are going to be a fast runner — you could have other genes that make you run slowly.

“And genes that make you a good footballer or cyclist at age 15 might not be so helpful at age 25.”

Steele, a sprinter at the 2008 Beijing Olympics, says his genetic profile revealed he didn’t possess the “sprinter’s gene”, highlighting the complexities involved with testing. What does he make of the suggestion that the mind holds the greatest power?

“There’s definitely a behavioural-change aspect to genetic data and people will respond to what they believe are positive or negative findings. A good genetic testing company will help you to understand the function of your genes so that you can make best use of the motivational factors that they produce.”

There have been trials suggesting that some of the popular DNA kits do help people, but most of them were small and largely funded by the companies hoping to promote them. They include one conducted at the University of Central Lancashire that was published in 2016 and showed that participants — 28 young sportspeople and 39 male footballers — following DNA-matched training programs improved their performance almost three times more than those using traditional approaches to training.

Another by scientists at the University of Trieste in Italy involving 191 obese people and presented at the European Human Genetics Conference a few years ago found that those using a commercially available DNA diet kit lost 33 per cent more weight than those counting calories.

Still, Williams says he wouldn’t bother with them. “Even if you have a particular gene and accept that it might play a role in which exercise you do, it only adds up to a tiny part of the story. If a test says that you are a non-responder to endurance exercise, that just means that you won’t improve your maximal oxygen uptake by doing lots of it.

“If you want to shed body fat, it doesn’t matter what genes you have, you still need to get out there and run, cycle or swim.”

It’s too easy, he says, to jump to the wrong conclusion and let genes dictate how you move and eat with very little scientific basis.

“My advice if you have £150 ($272) to spend on a DNA kit is to use the money more wisely,” Williams says. “The best you are going to get is a load of false information and unknown facts about your DNA. Buy a good pair of trainers and a personal training or physiotherapy session instead.”

The Times