Can you really biohack your way to fitness using a DNA kit?

DNA testing companies claim that by using genetic information, they can make you stronger and fitter. But just how accurate are these kits and how much of an advantage do they really offer gym-goers? Writer Bridie Wilkins investigates.

In recent years, we’ve seen an explosion in lifestyle DNA testing companies starting up with the promise of providing personalised fitness advice. No longer do you have to waste time running or following a keto diet you hate – these companies claim that through your genes, you can work out which type of exercise and nutrition plan will work best for you. Appealing, right? 

Earlier this month, researchers from Edinburgh University found that 13 specific DNA sequences (genetic markers) were linked to severe cases of Covid-19. If genetic differences have been proven to determine how hard we’re hit by Covid-19, does that mean that we can use our saliva to determine pre-existing truths about other areas of health?

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What is a DNA fitness test?

According to Alun Williams, reader in sports and exercise genomics at Manchester Metropolitan University, it’s not such an absurd jump to go from Covid tests to fitness kits: “Assessing variations in DNA sequences gives insight into the protein content and function of various tissues and organs in each person,” he tells Stylist. “Proteins are the biological components that affect fitness-related traits.” 

In analysing these DNA sequences, we can (apparently) discover our most suitable training style and, in turn, achieve our goals more efficiently. 

DNAFit – one of the most popular direct-to-consumer genetic testing companies – published a study in 2016, showing that the participants who were genetically matched to a certain exercise type performed three times better after two months of training than those who were deliberately mismatched. Obviously, their own study would argue in favour of using genetic information to improve fitness. The company claims to “unlock your full health potential” using a cheek swab, with results assessing your power, endurance and strength response, how good you are at aerobic exercise, your injury predisposition, recovery time, muscle mass and VO2 max. 

There’s a gene called MCT1, for example, which is associated with endurance. If you’ve got it, you’ll (apparently) be able to run longer than someone who doesn’t have it (who may struggle to last a spin class).

How do DNA fitness tests work?

Identical twins aside, we all have a unique biological blueprint that’s made up of about 20,000 genes. These are found in every cell in our body and can be found in our saliva, blood, hair or stool. For the most part, saliva is the most common DNA collection point for the kinds of tests we’re discussing. 

All you’ve got to do is take a cheek swab, chuck it in the allotted tube and send it off to a lab for examination.

How accurate are DNA fitness tests?

Here’s where things become a little hazy. A study published in March 2018 found that up to 40% of the analyses of genetic disorders in some at-home testing kits were inaccurate. The study didn’t cover fitness kits and only looked at 49 samples – so was relatively small – but scientists concluded that at-home results needed to be backed up by more rigorous testing.

Our DNA is formed of 20,000 genes, with millions of existing variations. Commercial tests, however, only look at a handful of these genes and some suggest that the genes they examine may not be the ones that actually relate to our fitness. 

Williams explains that scientists are currently familiar with approximately only 5% of DNA variations – so the other 95% could well be the key to finding our fittest self. “Any DNA report given to an individual could easily be overturned by unknown DNA variations,” he says. As with any good novel, we don’t know the full story until we’ve read every page.

That said, Avi Lasarow, CEO of DNAFit and Prenetics EMEA, counters this by saying: “We use science to guide us and we stop where the science stops. If this wasn’t useful or applicable, there wouldn’t have been so much invested into fitness and nutrition genetic research around the world for many decades.”

How much attention should we pay to DNA results?

Interestingly, both Williams and Lasarow agree that at-home testing could be a starting point, but the results aren’t necessarily a diagnostic tool in their own right.

Williams explains that while inherited, genes could be a good primary indicator of fitness, contributing up to 80% of fitness-related differences between people. Muscle mass is a good example, with roughly 70% of our ability to build lean muscle being dependent on genetics. Saying that, Williams suggests that we should take these studies with a pinch of salt until scientists are familiar with all DNA variations. Instead, he suggests looking to your ancestors and using their experience as a more precise guideline for your individual case. Does your grandad still run 10km every morning, despite being well into his 70s? Is your mum eternally injured? The chances are that you’ll share similar characteristics. 

Lasarow agrees that genetics make a solid baseline when it comes to improving our fitness, but says that your gender, age, weight and exercise frequency will help provide a fuller picture. “We stress this on our websites and in our reports,” he adds. “Genetics are a factor to build upon.”

If you struggle to run a 5km, there is *some* evidence to suggest that your lack of cardio capacity is inherited.

DNA kits – fab or fad?

If you’re thinking of getting a test and using that to determine your fitness regime, you probably won’t reap many benefits. However, by combining genetic knowledge and lifestyle factors, you have a far better chance of working out which type of exercise is likely to help yield the best results and how to avoid injury.

Look on any commercial genetic testing website, and you’ll see that they’re often promoted as being suitable for everyone over 18. Lasarow says that this is because most studies have only been carried out on adults. Once over the age limit, everyone from athletes to those who barely exercise can benefit from the results (or so claims Lasarow).

Williams, on the other hand, believes that only elite athletes are in with a chance of obtaining any useful information from DNA tests.

“Considering the limitations of current DNA tests, we’d need an already detailed knowledge of our fitness that requires only slight adjustments, like elite athletes would have,” he says. “Several elements of their fitness have been established using sports science, nutrition and physical examinations.”

There’s also a racial health gap. The vast majority of scientific studies on DNA tests have been taken on white participants. Williams advises that, for this reason, those who don’t fall into this category may want to avoid genetic testing. “Even less is known about how DNA variations affect fitness-related traits in non-white populations,” he explains.

4 DNA tests and what they test for


Cost: £199

Type: Saliva

What it analyses: Optimal training type, power response, endurance response, strength response, aerobic trainability, recovery efficiency, injury predisposition, Achilles injury risk, ACL injury risk, lower back injury risk, muscle mass.


Cost: £149 (health and ancestry test)

Type: Saliva

What it analyses: Muscle composition, saturated fat and weight, caffeine response, alcohol response, genetic weight, lactose intolerance, deep sleep, sleep movement.


Cost: £107

Type: Cheek swab

What it analyses: Recovery efficiency, metabolism, muscle strength, joint strength, endurance, red blood cell production, power performance.

Fitness Genes 

Cost: £129 

Type: Saliva

What it analyses: VO2 max, fat-burning potential, metabolism, muscle strength, insulin function, recovery efficiency, muscle fiber composition.

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