Can a gene test reveal what exercise works best for you?

We try out the new DNA kits that claim to determine whether you’re a sprinter or a plodder . . .

PLODDING around the park. Choosing salad, not chips — again. Sometimes staying in shape can feel like a slog. But what if the answer wasn’t that you needed to do more exercise, but simply to exercise in the right way for you, according to your unique genetic make-up?

That’s the tantalising promise of a new breed of home genetic tests, which claim to pinpoint the best types of exercise and nutrition for you to get the best results.

Typically costing from £50 to £250 a go, home DNA tests are big business. They’ve been taken by millions worldwide, with some estimates predicting the market will be worth £7 billion in the next four years.

There are now at-home gene tests for all sorts of (scientifically dubious) purposes — from skincare advice to services promising to find you the perfect partner based on your DNA.

But can such a test really act as a pocket personal trainer? To find out, I tried two of the tests — DNAFit (prices start at £199) and FitnessGenes (from £149) — and asked the experts to assess the results.

Taking the tests is easy, if a little undignified. FitnessGenes sends a test tube for you to spit into, while DNAFit requires a swab from inside your cheek.

You send your sample to a lab and, from this, both tests look at the versions you have of particular genes linked to certain diet and fitness traits. You get the results in an online report a few weeks later.

There has been encouraging research around following a genetics-based diet or exercise programme. Italian research presented to the European Society of Human Genetics in 2014 suggested people following a diet based on their genetics — for example, where those whose genes suggested poor fat metabolism were put on lower fat diets — lost 33 per cent more weight compared to a control group, even though they consumed a similar number of calories.

MEANWHILE, a study published in 2016 in the journal Biology of Sport found athletes who trained in a way that matched the results of a genetic analysis (done by DNAFit) performed better than a group given a training plan that was a deliberate mismatch with their genes.

The analysis identified whether the athletes were better suited to high-intensity ‘power’ training or lower- intensity ‘endurance’ training for eight weeks.

So, what did my genes reveal about my ideal fitness routine? On the face of it, quite a lot. According to DNAFit, for example, my genes suggest that I need a fairly average recovery time. This verdict is based on seven different genes, including some that may influence levels of inflammation and oxidative stress after exercise.

‘Around 48 hours between hard workouts would be about right for someone with an average recovery rate,’ says Andrew Steele, head of product and professional sport at DNAFit. (Someone with ‘fast’ recovery genes, he adds, could get away with back-to-back workouts, while someone with ‘slow’ recovery genes might need 72 hours).

Allowing muscles time to rest and repair is important to prevent injury and make sure you get the most out of subsequent workouts.

I can’t say I’ve ever given it that much thought: like many, my issue is whether I do enough exercise, rather than worrying that I’m doing too much, but the result makes sense. I’m a regular runner and tend to leave at least a day between runs, as otherwise, my legs feel too sore.

However, I apparently have a higher-than-normal risk of softtissue injuries. It’s news to me — despite having trained for several half-marathons, I’ve never yet had a serious sports injury.

The result from both tests I’m most intrigued by is the fact that my genes are apparently weighted more to ‘power’ than ‘endurance’.

This relates to genes linked to particular types of muscle fibre, blood vessel growth, the ease with which you build muscle and how efficiently carbohydrates are used for fuel, according to DNAFit.

In practical terms, this means to get the best results, I should be doing shorter, more intense workouts, rather than longer, steadier ones — think sprints, interval training and short sessions with heavier weights.

As someone who tends to prefer longer, ambling runs, I don’t think of myself as having the muscles of a sprinter. I’m definitely more of a plodder.

But then I think of my most recent half-marathon: I’d ended up doing shorter, faster training runs than my usual long, steady jogs and finished in my fastest time by a modest four minutes.

Could this be proof that I should train according to my genes?

The recommendations extend to my diet, too. DNAFit, for instance, recommends taking caution with my refined carbohydrate intake, because I have variants of genes that may affect the way my body responds to foods such as bread and pasta, which are broken down quickly into sugar. These genes may mean I am more likely to gain weight or become insulin-resistant if I eat too many of these foods.

It describes my optimal diet as low-carb, as opposed to low-fat or Mediterranean. So what do geneticists make of my results? First, the actual DNA analysis offered by these tests is likely to be accurate, says Dr Giles Yeo, the director of genomics at the Medical Research Council’s Metabolic Diseases Unit at the University of Cambridge.

The problem, he adds, is in the interpretation of the data. while the results are based on research that has linked genes with particular traits, ‘this doesn’t mean it will be predictive on an individual level — there’s no way of knowing for certain you have that type of muscle fibre or response to fat’.

For this reason, he’s unconvinced about recommendations around recovery time, muscle type, aerobic response and carbohydrate and fat sensitivity, noting that any result that’s based on more than one gene is not definitive.

In fact, according to Dr Yeo, the only results that can be taken at face value here are those for lactose tolerance and caffeine sensitivity (both tests tell me I am capable of tolerating lactose in dairy, but I am a ‘slow metaboliser’ of caffeine, meaning it will have a much longer, more noticeable effect on me than someone with ‘fast’ versions of the ‘caffeine gene’).

This is because these results are based on a single gene. You either have a particular version of the gene — and the trait it confers — or you don’t. ‘what these tests do is intermingle stuff they can say definitively with things they absolutely cannot,’ adds Dr Yeo. Professor Munir Pirmohamed, the NHS chair of pharmacogenetics, agrees: ‘I’m not against these tests at all, but the advice they give needs to be taken with caution. The evidence base behind telling you which kind of diet you should be on is pretty poor.’ Yet Avi Lasarow, CEO of DNAFit, disagrees. ‘Led by our independent scientific advisory board, we see a growing body of evidence that the impact of genetics on our diet is significant,’ he says. ‘This is backed by the rapidly accelerating marketplace and feedback from 80 per cent of our customers that this information helped them achieve their goals.’

Professor Pirmohamed believes these tests will, in future, be able to extract far more than they can now. ‘Eventually, we’ll have lots of evidence suggesting that different people need different, personalised diets, and different kinds of exercise,’ he says. ‘ But it’s not quite there yet to be able to make individual recommendations.’

So will I be following my genetic fitness plan? I’m afraid not. I’m sure four workouts a week, a bit more sprinting, and less pasta and cake would indeed make me slimmer and fitter — but sticking to it might prove less straightforward.

As for cutting back on coffee, while it might be in my DNA, it’s just not ‘me’.