Genetics is amazing. It tells us so much about humanity and it’s a minefield of information. Admittedly, it’s a minefield that has only just been touched upon, but scientists argue that genetics is the answer to everything – so does that include diet and fitness? Companies like DNAFit say yes. They argue that the results of a DNA test will allow you to develop a personal gene-based diet and fitness plan that works for you – and that brings a whole new meaning to the term ‘tailor-made’. It may sound like a futuristic way to develop a fitness plan, and the possibilities are nothing if not intriguing, but there are some questions of the efficacy of these tests. So can they really help you improve your diet and fitness? And are they worth the money?

What They Do

At a very basic level, our genes dictate everything. Like a computer code written into us before we’re even born, our genes influence everything we do in life and how we respond to different external stimuli – and that, of course, includes how we respond to different foods and exercises. It makes sense, then, that a DNA test could tell us what foods are best for us to eat and which exercises will have the best results. Companies like DNAFit are now branching out from working with only professional athletes to providing home-testing kits and the results can provide information about your sensitivity to carbohydrates, salt, saturated fats, lactose, and gluten. You can find out about your specific requirements when it comes to anti-oxidants and vitamins, and your ability to process things like caffeine and alcohol. Not only that, but you can discover which sports suit you best – endurance sports or power sports? These tests even claim to tell you how likely you are to injure yourself during training and how long it will take you to recover[1].

DNAFit’s chief tester, Andrew Steele, explains how it works. He says “some people are more efficient than others at extracting energy from food. A responder to carbohydrates gets a bigger increase in blood glucose from carbs so they don’t need as much and should be careful not to eat too much. But if you are a low responder you might need more carbohydrates to meet your body’s needs”[2]. The tests are not new, of course. Professional athletes have been using tools such as these for years, but now, as home-testing kits have become available, the use of DNA tests as prescriptive information is becoming more widespread. In the parts of the UK’s National Health Service, they are trialing a scheme in which overweight and obese patients take a test and then have a tailor-made diet plan designed specifically for them[3], and it’s believed to be working. It’s estimated that people who diet using recommendations from genetic tests loose on average 33% more weight than those who dieted using other methods or plans[4]. What’s not to love?

A Small Window to a Big World

These are big claims to make and it would be fantastic if they were accurate, but the truth is that genetic profiling is still in its infancy and many scientists argue that these tests are, for now, simply not worth the money. For a start, they are only looking at a tiny part of the genome. There are around 10 million gene variants in the human body, but tests like these look at only around 45 of them[5]. That’s 0.0000045% of all possible gene variants. Of course, not all gene variants are relevant, and of course, not all have been as scientifically validated as the 45 tested, but that percentage is still shocking and shows that perhaps science has a way to go before these tests can be truly accurate.

Mark Thomas, a professor of evolutionary genetics at the University College, London agrees and says that the tests only provide a small glimpse into genetic profile. He goes on to say that “these tests are only weakly informative. If you want to know how good someone is likely to be at sport, you’ll probably get a better idea by looking at them and their body shape”[6]. Perhaps then, these tests can’t possibly provide comprehensive results simply because scientists simply don’t have a comprehensive understanding of the human genome yet.

What’s more, genes aren’t everything. As the nature/nurture debate rears again, Duncan French at the English Institute of Sport argues that “there are so many other variables to fitness and sports performance”[7]. Professor Jess Buxton, a research geneticist, thinks similarly, and claims: “without knowing everything about someone and all the genetic variations they carry, along with all the lifestyle components of their lives, it’s hard to make predictions about people based on looking at a few genes”[8]. Performance nutritionist James Collins confirms this, saying “there’s insufficient evidence…we’re a long way away from cause and effect”[9].

But What’s The Point?

Even if the results were accurate, and even if the tests worked, what if it ended up being counterproductive? Imagine someone who is struggling to lose weight suddenly discovers that they have the ‘fat gene’ or a predisposition to putting on weight – will they just give up? And isn’t the information that these results provide simply information that you could learn through experience and trial-and-error? And perhaps, just perhaps, these tests take the sportsmanship out of sports and fitness. “Before anything else,” Duncan French says, “you have to enjoy it; you have to have a mental engagement and a reason for doing what you’re doing. Otherwise, regardless of DNA profiling, you aren’t going to maximize your potential”[10].


[1] Helen Croydon, 2016, Could a DNA Test Help You Get Fitter? [online]. Available at: [Accessed: 02/21/2016]

[2] Helen Croydon, op. cit.

[3] Ibid.

[4] Nina Combs, 2014, What a DNA Test Taught Me About Diet and Exercise [online]. Available at: [Accessed: 02/21/2016]

[5] Helen Croydon, op. cit.

[6] Ibid.

[7] Natalie Goodchild, 2015, Are Fitness and Diet DNA Tests Worth the Investment? [online]. Available at: [Accessed 02/21/2016]

[8] Anne Magee, 2013, The New DNA Fitness Tests [online]. Available at: [Accessed 02/21/2016]

[9] Natalie Goodchild, op. cit.

[10] Ibid.

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DNA Fitness Tests: Are they worth it? by UrbanSculpt Staff Writer Victoria Froud, MA is licensed under a Creative Commons Attribution 4.0 International License.
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