Tim Spector, professor of genetics and co-founder of the Zoe personal nutrition company, is recovering from a mild illness when the Observer meets him and the firm’s other founders.

“People expect Tim to have the immune system of perfection,” jokes co-founder and chief executive Jonathan Wolf, “but even he, with his almost perfect microbiome, occasionally gets sick.”

Since its launch in April 2022, more than 130,000 people have signed up to Zoe’s personalised nutrition programme, which aims to improve gut and metabolic health. Spector is a familiar figure on TV and radio, and through his books The Diet Myth and Spoon-Fed.

Zoe customers can be spotted by the circular yellow arm patch that means they are wearing a blood sugar sensor. Carrie Johnson, wife of former prime minister Boris Johnson, recently revealed on Instagram that she had signed up. Television presenter Davina McCall is one of its biggest advocates.

Zoe (“life” in Greek), gives personalised advice via an app on what users should eat, based on the results of gut health and blood fat tests and 14 days of blood sugar monitoring, all done at home and sent off to a lab.

Spector does not believe in miracle diets. But he has faith in the microbiome – the trillions of bacteria, viruses and fungi living in our gut – which as well as digesting food also play a vital role in regulating our immune system and our brain chemistry. “We’ve now realised that food is the most important choice individuals can make for their health,” he says.

Born in north London, he trained as a doctor, then became professor of genetic epidemiology at King’s College London. In 1992, he set up a registry of 15,000 adult twins at St Thomas’ hospital in London, and his TwinsUK and Predict studies have shown that even genetically identical people respond to foods very differently.

He had his first eureka moment in 2012 during the twin study when he looked for factors that would explain why some had different diseases. “It was only when I tested the microbiome, that was the first thing I’ve ever found that was radically different between identical twins.”

He had another “aha” moment on a skiing trip, after suffering a mini-stroke that left him unwell for three months. He reassessed what he knew about healthy eating.

“I was moving away from being an epidemiologist, studying populations, to wanting to give individuals precise advice. And that first individual was me.”

Spector discovered that his high-carb breakfast of muesli with low-fat milk and orange juice was “super unhealthy for me: it left me drained, tired and probably made me hungrier. So I was overeating, which meant I slowly gained a kilo a year.”

These days, he does not eat until 11am, when he has kefir and full-fat yoghurt with berries, nuts and seeds, with a plant-based meal such as curry for lunch.

Wolf studied physics at Oxford and spent 20 years working for tech companies. He gained experience in artificial intelligence in his previous job as chief product officer at Criteo, one of Europe’s biggest tech firms. He says he overcame food intolerances by ditching highly processed carbs and switching to a plant- and fibre-rich diet. “At breakfast, I’m hungry, so yoghurt and nuts is not enough. I still have some bread, but I have rye bread and I often have avocado as well.”

The third co-founder, and Zoe president, is George Hadjigeorgiou, an engineer from Greece. He set up the largest online food takeaway company in Greece, e-food.gr, which was sold to Germany’s Delivery Hero in 2015. He had high cholesterol but cut it by 40% by switching to berries, nuts and seeds, fish, pulses and extra virgin olive oil that he brings from Crete every year.

He and Wolf had worked together at Yahoo. After hearing a public talk by Spector about the twins study, they decided to put together a personalised nutrition business pitch.

“I said we really needed to do a big science project to prove this,” recounts Spector. “And you guys are gonna go and raise several million for this to happen. I really wasn’t sure whether I’d see them again.”

But they raised €7m of seed money and Zoe was born in 2017. Then came Covid. The trio decided to pause the project in March 2020 and launched a Covid symptom tracker app, which went on to have more than 4 million users.

“It really proved that if you could get millions of people to participate in science at home, you can do better science than has ever been done in laboratories,” says Wolf.

Spector’s five top nutrition tips include eating a plant-rich diet, fasting overnight and reducing ultra-processed foods – from 60% in the UK to close to the 15% in Mediterranean countries.

A decade ago, his son Tom, then a student at Aberystwyth University, volunteered, as an experiment, to eat just McDonald’s food for 10 days. Tom reported feeling good for three days, but then became lethargic and unwell. While he didn’t gain weight, Spector says, “what was really worrying was that he lost about 30% of his microbial species, and even now, his microbiome is below average”.

Zoe has identified almost 5,000 never-before-seen gut bacteria. Of those, 100 were strongly associated with health across all 35,000 participants – 50 good and 50 bad. This feeds into the app and members’ personalised scores will be updated over time.

Some doctors have reportedly said that personalised nutrition apps can cause healthy people unnecessary worry. Zoe says it “delivers evidence-based advice and a clinically validated personalised nutrition programme designed to improve health”.

The company will this week release the results of its recent Method study, showing that people who followed Zoe’s personalised programme for 18 weeks saw improvements compared with a group receiving standard dietary advice. The Zoe group lost weight and had healthier body composition, improved blood fats and a better gut microbiome.

Critics had said earlier that the trial was flawed because people knew which group they were in. Among those critics are Deborah Cohen, former Newsnight health editor, and Margaret McCartney, a GP and writer, who wrote on UnHerd: “Zoe is only one of hundreds of apps that measure our biometrics in this age of the quantified self. But … are these promises of personalised advice based on sound medicine?”

A recent surge in demand means new Zoe users have to wait several weeks for their testing kit. It has so far attracted $101m in investment from several venture capital firms, Dragons’ Den’s Steven Bartlett, and NFL champions Eli Manning and Ositadimma “Osi” Umenyiora.

Results filed with Companies House show Zoe made a pre-tax loss of £10.5m in the year to the end of August 2022, up from £7.9m the year before, despite a jump in revenue to £5.9m from £1.8m, as distribution and salesforce costs also surged.

Joining the programme is not cheap: a starter kit costs £299.99 and membership starts at £24.99 a month. The company says the price will come down as lab testing gets cheaper, and in the meantime it provides free health advice through podcasts. It also hopes to work with the NHS in future and says its member database is anonymised. And data is also not shared with health insurers.

“We know from our Covid discussions how painful it is to get anything agreed in the NHS, but the three of us would love the NHS to adopt the Zoe programmes in some form or another,” Spector says.

CV

Tim Spector

Age 65

Family Married with two children.

Education University College School, London; St Bartholomew’s hospital medical school, London.

Last holiday Istria, Croatia.

Best advice he’s been given “Ensure you enjoy what you’re doing, otherwise life will be boring.”

Biggest career mistake “I applied for very bad jobs, but luckily never got them.”

Words he overuses “Marvellous” and “complete rubbish”.

How he relaxes Sports, cooking, red wine and meditation.

Jonathan Wolf

Age 48

Family Married with two children.

Education Physics at Oxford University.

Last holiday Italy.

Best advice he’s been given “Do something you love.”

Biggest career mistake “Joining a dotcom firm in March 2000, on the day the Nasdaq bubble popped. At the time it was worth billions, and eight months later I was laid off.”

Words he overuses “Amazing”, “actionable advice”.

How he relaxes “I am known across the company for my need for a nice cup of tea at frequent intervals.”

George Hadjigeorgiou

Age 48

Family Married with two children.

Education Anatolia College, Greece. Studied mechanical engineering at Tufts University, Boston, and Massachusetts Institute of Technology.

Last holiday Skopelos, Greece.

Best advice he’s been given “Truth is the beginning of beautiful outcomes.”

Biggest career mistake “Working for big companies longer than I should have.”

Words he overuses “Focus”, “orthogonal”, “double-click”.

How he relaxes “Going to a musical with my family, tennis, karaoke – if one can bear my terrible singing.”