The diet that is right for you: putting a personalised nutrition app to the test – The Guardian

A gadget-rich programme says it will find out how you react to foods and teach you to eat the best ones
For decades, dietary advice has been notoriously faddy, swinging from the low-fat, high-carb guidance of the 1980s and 1990s to the low-carb or intermittent fasting diets recommended in more recent years.
But one programme claims to be different: it promises to test how your individual body responds to different foods, and then teach you to eat the right ones for your biology.
And it all begins with eating a packet of muffins, a novel twist even as the world of dieting becomes increasingly esoteric. But this programme, created by the team behind the Covid symptom tracker app used during the pandemic, claims that its aim is better long-term health rather than weight loss.
The Guardian was invited to be the first UK newspaper to try the programme by Prof Tim Spector, the scientific co-founder of Zoe, the firm behind apps tracking coronavirus and, now, nutrition. And the big lesson I have learned so far is “less sourdough, more nuts, cheese and avocados” – at least for me; someone else may receive entirely different advice.
The idea was born out of research suggesting that even identical twins respond differently to eating precisely the same meal. By identifying which foods lead to large, prolonged spikes in blood sugar or fats – both of which can trigger inflammation, contributing to the development of diseases such as diabetes, cancer, heart disease or dementia – the idea is that you can learn to avoid these foods, or combine them with others to help minimise these spikes.
Through the post, I received a finger-prick blood test, several packets of standardised muffins, a continuous glucose monitor that I attached to my arm, and a stool sample kit to analyse my gut microbes. I was also told to download the Zoe app, and was connected to a personal nutrition coach.
Each day for the next two weeks I would log everything I ate in the app, sometimes eating several muffins and taking a blood test to measure the amount of fat in my blood. This, combined with the data from my food log, glucose sensor and poo sample, would be crunched by an algorithm to calculate my individual responses to the foods I had eaten – and predict my responses to many more.
Spector may be best known for his work leading the Zoe Covid study, but the company’s nutrition programme was in the works long before thepandemic. Now that continuous lockdowns have endowed so many of us with an extra “Covid stone”, Spector is on a mission to change the nation’s attitude to food.
The goal isn’t weight loss in itself, but better long-term health. Interim clinical study data shows that after three months on a personalised Zoe plan, 82% of participants had more energy, 83% no longer felt hungry, and members experienced an average weight loss of 4.3kg.
Dr Sammie Gill, a spokesperson for the British Dietetic Association, said: “I’ve no doubt that in the future, personalised nutrition which offers targeted interventions and tailored recommendations based on an individual’s physiological and microbiological responses will become part of routine clinical practice. It’s a real paradigm shift and is based on the premise that dietary guidelines which offer standardised advice to all are too simplistic.”
Even before I received the results, my glucose sensor had provided some interesting insights. For instance, my go-to breakfast, a slice of sourdough slathered in butter and honey, would send my blood sugar soaring and then crashing down, but if I ate the same breakfast immediately before exercise, the effect was far less pronounced.
“These sugar spikes also tend to be followed by a sugar dip in around one in four people, and that then causes increased hunger and reduced energy levels, so you tend to eat more,” Spector said.
So, when my results finally did arrive, I wasn’t too surprised to learn that blood sugar control isn’t my metabolic strong point – although mine is about average. This does not mean that simple carbs, such as white bread, are now forbidden.
Under the Zoe system, each food is assigned a score out of 100, specific to you as an individual. So, whereas white rice earns me a score of 17-42, depending on the type, if I combine rice with split peas, this rises to 75 – meaning I can consume it regularly.
Happily, I can report that my blood fat control – how quickly I clear it from my circulation – is excellent, although this doesn’t mean I can consume cakes and whipped cream with abandon, because the app also considers their effect on the growth of good and bad gut bacteria (and these foods promote bad ones). However, it does mean that avocados, cheese, greek yoghurt and nuts are now regular fixtures on my menu.
Though I’m happy to eat more of them, I worry about the effect on my waistline. However, my coach tells me not all calories are created equal, and that they should be regarded as an average indicator of energy provision.
I also received a score for my microbial health, the diversity of which is below average, possibly due to a prolonged course of antibiotics. But it is fortunately rich in bacteria that support blood glucose control. I was given a list of foods to try to boost their levels further – mostly vegetables and nuts, but also green tea and black coffee.
The total cost of the test kit is £259.99, and most people commit to a four-month programme at £34.99 a month.
Zoe is not the only company developing this concept of personalised nutrition, but it is one of the first to hit the UK market. Prof John Mathers, the director of Newcastle University’s Human Nutrition Research Centre, is broadly supportive of the idea, calling it “based on high-quality research” with the power to “help motivate individuals to eat more healthily”.
His concern is over the rush to commercialisation, and that it may be a simplistic way to predict long-term health. He also dislikes the suggestion that it is unnecessary to limit energy intake to lose weight. “These are seductive ideas, but in my view the available evidence is too limited to be confident that they are correct.”
However, I love that the app provides real-time feedback on what you’re considering putting into your mouth. Already, I’m drinking less wine, and have noticed I am now less prone to craving biscuits and chocolate after meals.
I am also consuming vastly more vegetables – particularly at lunchtime, when my typical sandwich has been replaced with a wholegrain or bean-based salad, with plenty of leaves and seeds. Even if I don’t lose weight, my gut microbes will surely thank me. Just don’t stand too close to me in an enclosed space.

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