Can a gene test really help you get fitter?

PLODDING round the park. Choosing salad, not chips – again. Sometimes staying in shape can feel like a slog.

So what if the answer wasn’t that you needed to do more exercise, but to exercise 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 pin-point the best types of exercise and nutrition for you in order to get the best results.

Typically costing between £50 and £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 around £7 billion in the next four years.

There are now 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 myself — DNAFit (prices start at £199) and FitnessGenes (from £149) — and then asked the experts to assess the results.

Taking the tests is easy– if slightly undignified. FitnessGenes sends you a test tube which you have to spit into, while DNAFit requires a swab from the inside of your cheek. From this, both tests look at the versions you have of particular genes linked to certain diet and fitness traits. You send your sample off to a lab and get the results, in the form of an online report, a few weeks later.

There has been some encouraging research around following a genetic-based diet or exercise programme.

Italian research presented to the European Society of Human Genetics in 2014 suggested that people following a diet based on their genetics — for example, 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 ate a similar number of calories.

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

The analysis identified whether the athletes were more 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. For example, according to DNAFit, my genes suggest I need a fairly average recovery time afterwards.

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,’ suggests Andrew Steele, head of product and professional sport at DNAFit.

(Someone with ‘fast’ recovery genes, he says, could get away with back-to-back workouts, whereas 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 consideration — like many, my issue is whether I do enough exercise, rather than worrying about whether 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 soft-tissue injuries. It’s news to me. Despite having trained for several half marathons, I’ve never yet —touch wood — 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 of which you build muscle and how efficiently carbohydrates are used for fuel, according to DNAFit.

In practical terms, this means to get 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 certainly 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, more by accident than design, and I 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 caution when it comes to my refined carbohydrate intake. This is 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 Mediterranean or low fat.

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, director of genomics at the Medical Research Council’s Metabolic Diseases Unit at the University of Cambridge.

The problem is in the interpretation of the data, he says. 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,’ he explains.

For this reason, he’s unconvinced about recommendations on recovery time, muscle-type, aerobic response, 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 two results that can be taken at face value here are the results for lactose tolerance and caffeine sensitivity (both tests tell me I am capable of tolerating lactose in dairy but I’m 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, 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.’

Avi Lasarow, CEO of DNAFit, however, 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 one day be able to extract far more than they currently can. ‘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 from now on? 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’.