At the end of January, I embarked on a voyage of DNA discovery aiming to improve my health and fitness, and took a test that promised to provide a bespoke diet and training regime based on my genes.
As I reported back then, DNA-based regimes have become something of a trend, claiming to be the latest and most medically advanced way to get into shape.
I opted for FitnessGenes (£129, fitnessgenes.com), which involved an at-home saliva test and a short questionnaire about my height, weight and activity levels.
Two weeks later, my results were available via their website: information about 48 of my genes; a daily diet plan and a seven-day exercise programme.
DNA-based fitness regimes have become a trendy, ‘medically advanced’ way of getting in shape
All health and lifestyle advice is based on my genetic make-up, they say, with attention given to specific genes responsible for traits such as overeating, fat formation and lactose intolerance.
The advice is very specific: according to my DNA, I need to consume 1,417 calories a day: 178 grams of carbohydrates, 57 grams of protein and 52 grams of fat.
Despite the fact that I am seven-and-a-half stone, which at 5ft 4in gives me a (slightly underweight) BMI of 17.5, my recommended daily intake is 500 calories below that considered sufficient for a moderately active, adult woman.
FitnessGenes say a calorie reduction is necessary because I have two copies of an FTO gene type which puts me at high risk of obesity.
My report also tells me I may be prone to ‘disinhibited’ – that means compulsive – eating.
They say I should follow a low-fat, high-protein diet and manage hunger by drinking lots of water and taking daily doses of glutamine (an amino acid) supplements.
As for fitness, my presentation of the PGC1A gene, responsible for aerobic capacity, means I would find high-intensity interval training especially beneficial.
If I were to follow the ‘bespoke’ recommendations, I’d indeed lose weight – about two pounds per week, according to NHS choices.
This would mean that within a month, I’d be severely underweight, increasing my risk of osteoporosis, fertility problems and chronic exhaustion.
The expert view
‘Your case is a classic example of why these tests don’t work,’ says geneticist and obesity expert Dr Giles Yeo.
Dr Yeo, who studies ‘fat genes’ at Cambridge University, says: ‘While your FTO expression is partially associated with increased obesity risk, its predictive value is slightly better than flipping a coin. And it’s obvious you’re not overweight.’
But these DNA tests are widely used by geneticists, so surely my results are worth something?
Dr Yeo says: ‘These tests are great for finding out about your genealogy – what percentage Ashkenazi Jew you might be, for example – but that’s about it.’
Dr Dan Reardon, founder and CEO of FitnessGenes, says: ‘The results reflect whichever goal you set, for example weight loss, hence the calorie deficit.
‘BMI is a crude measure of health that doesn’t account for muscle or body-fat percentage. However, we will take your concerns on board and offer extra advice for people at the low weight end of the scale.’
I might give the exercise bit a go (I didn’t need a DNA test to tell me that my aversion to the gym might need addressing).
But the ‘cutting-edge’ diet advice? I’ll give it a miss.