Forget everything you've ever heard about calorie counting and portion control. The Zoe diet programme wants to reteach us how to eat for optimum health. Our health writer's results surprised even her!

The popularity of personalised health and wellness shows no sign of slowing down. We’re now using at-home test kits to check for everything from gut health to hormone levels and even cellular ageing. The latest runaway success is the Zoe diet programme, a bespoke approach to eating for optimum health, which has more than 200,000 people on the UK waitlist. The Zoe diet is an at-home test that's part personalised diet, part research study pioneered by Professor Tim Spector, author of The Diet Myth and Spoon-Fed. He's also the man behind the Zoe Health Study app, into which millions of us input our Covid symptoms. Professor Spector and Zoe were also responsible for the Blue Poop Challenge, another crowd-sourced research study that used blue muffins to measure gut transit time. 

The Zoe programme, or Zoe diet as it is being dubbed, wants to reteach us how to eat in line with our biology. It does this by offering at-home testing of blood glucose (via a continuous glucose monitor), blood fat (via a finger prick test), and the gut microbiome (via a stool sample) to assess how you personally metabolise foods, mainly carbs and fats. Zoe then uses this information to provide guidance via an app on how to make better food choices to suit your unique metabolism. 

Initial results showed that after three months on a personalised Zoe plan, 82 per cent of members reported having more energy, 83 per cent no longer felt hungry, and the average weight loss was 4.3kgs. 

The principle seems a sound one - generic or faddy diets don't work because everyone's metabolism and gut microbiome is unique and we all respond to food differently. For life-long gains we need to look at what's happening inside us, quite literally. 

So far 37,500 people have taken the Zoe test since it launched in April 2022; you've probably already spotted people walking around with these metabolic trackers stuck to their arms, forming part of an elite new dietary club. The brand says there are currently 230,000 more on the UK waitlist. 

Does the Zoe diet work? Read on for the surprising results one writer had when she put it to the test.

What is the Zoe diet?

Zoe is a personalised nutrition programme based on the results of one of the most extensive sets of studies into nutrition of their kind, known as the Zoe Predict Studies, carried out by researchers from King’s College London, Harvard University and Stanford University, led by nutritional scientist Dr Sarah Berry of King's College.

Published in 2020, they involved more than 1,000 people, including 660 identical and non-identical twins and looked at how different individuals' metabolism responded to carbohydrates and fats, by measuring blood sugar spikes, while also examining the state of their gut bacteria to see which good and bad bugs were present.

Participants were given three muffins, the first two to test blood sugar and the third to measure blood lipids (fats), after which their blood sugar and fat levels were measured to see how they metabolised glucose and fat. 

Zoe's research found that people respond significantly differently to the same foods. Some experienced a huge blood sugar spike after eating the same muffin as others whose blood sugar was only slightly raised. This suggests everyone's response to food is indeed unique - even among identical twins - and crucially that calorie-counting is utterly flawed because people can eat the same calories and yet respond differently.

The at-home Zoe programme, which comes with specially made muffins and blood monitoring testing kits, allows you to replicate these studies from home and see how your particular makeup affects the way you process food. The Zoe app then dishes up suggestions for foods that will help you manage your blood sugar response to keep dietary inflammation at bay and also suggest foods that combine well to optimise your body's blood sugar response to meals. Food combining to buffer blood sugar spikes is a key part of the Zoe programme.

Why does blood sugar response matter for health? 

The Zoe diet aims to get you on a more even keel regarding your blood sugar, avoiding spikes and dips. Why? There are short and long-term implications of being on a constant glucose rollercoaster, says nutritional scientist Dr Federica Amati, who provides nutritional guidance for Zoe. “First of all, you can get really hungry. When you have a glucose spike, and then it crashes, especially after a very sugary meal, your insulin gets pumped out quickly to try and clear it. This can make you feel starving because your body thinks you don't have enough glucose." 

People whose glucose metabolism is awry often report feeling hungry all the time, as well as being tired and having a lack of energy, poor sleep quality and sometimes even cold sweats and feeling faint, she says.

Longer-term, having high glucose and fat levels in your blood can contribute to chronic-low grade inflammation (stress and sleep deprivation can do that too). This is linked with developing serious diseases, such as type 2 diabetes, heart disease and Alzheimer's. 

"We have to remember that glucose is our body's number one energy source, and our brain’s preferred energy source, so it's not a good thing if we start having not enough glucose in our bodies, but there's only a certain rate at which our bodies can convert it [to energy], " says Dr Amati. What's more, she adds, our cells age more if we have elevated blood glucose levels under a process called glycation, while high blood fat levels are bad for vascular health.

How does the Zoe diet work?

You sign up via the website, but there's a waitlist - Zoe says it is inviting people to join as quickly as possible. For £259.99 you receive a Zoe test kit to complete over four days. You’re free to stick your muffins in the freezer and start on a day that suits you. Support is available on demand from Zoe nutritionists via the Zoe app. 

The kit contains:

  • Gut microbiome test in the form of a pot for a stool sample, plus a paper poo catcher that you sling across your toilet bowl. Your poop sample is used to examine how diverse your microbiome is - or how many good and bad gut bugs are living in it-  the health of which is closely linked to things like digestive disorders, your immune system and even mental health.
  • Blood fat finger prick test. This analyses how quickly you clear fat from your blood following a meal. This is one of the best indicators of your risk of developing heart disease. If fats hang around in your blood for too long after eating, it can cause increased inflammation, among other things.
  • Three sets of muffins to eat on days three and four. For example on day 3 you eat three muffins for breakfast followed by four hours of fasting, then two muffins for lunch, wait two hours and then perform your blood sugar test. On day 4 you eat two muffins for breakfast.
  • Real-time blood sugar sensor, if you opt into Zoe's scientific study. This is a round 3D disc that you stick to the top of your arm and leave in place for 14 days. A tiny needle in its centre pierces your flesh and sends readings to your phone, showing real-time fluctuations in your glucose levels. The glucose is picked up from the fluid that surrounds the cells just beneath your skin. You're able to test how 'well' you metabolise carbs by checking for fluctuations in your blood sugar levels. Large spikes and dips are considered 'unhealthy' as they are linked to chronic diseases such as obesity, diabetes and heart disease.

The Zoe test is linked to the Zoe app, and this app guides you through every step of the procedure day by day. There’s a second app involved in the test, this one run by Librelink, the company that manufactures the blood sugar monitors. The Librelink gives you a running commentary on your blood sugar levels. 

Getting your personalised Zoe diet results

Six weeks after sending your samples back to the lab, you'll receive three personalised Zoe scores: one for fats, one for carbs and another for your microbiome. You'll receive two PDFs, giving details of your microbiome and your body’s responses to sugar and fat. Later in the app, you'll receive personalised scores as to how well more than 1,000 different foods suit you as well as tips on which foods combine well to help stabilise your blood sugar.

When it comes to food scores, it's the higher the score, the better, Dr Amati explains. "It's trying to fill your tank to the top instead of restricting your calories or cutting out food groups." As well as no calorie counting there is no food weighing or limiting of portion sizes, the idea is simply to get as many points as possible, which means you are eating right for your personal metabolism and also avoiding blood sugar spikes and swings.

How much does the Zoe diet cost?

The test kit costs £259.99 and can be paid upfront or in monthly instalments. Then you can choose from three membership plans if you want to receive on-going support.

• 1-month plan - £59.99 per month

• 4-month plan - £34.99 per month (upfront £139.96).

• 12-month plan - £24.99 per month (upfront £299.88).

Is Zoe diet good for weight loss? 

People lose on average 4.3 kgs (9.5lbs) in three months (writer Alexandra Heminsley who tested it for The Daily Mail lost a stone in six weeks), but weight loss is a happy byproduct of eating better rather than the goal. Interestingly our tester, below, didn't lose weight but felt immeasurably better.

Rather than being considered a weight loss programme, Zoe says it wants to help solve the major metabolic health issues caused by inflammation. "Diabetes, heart disease and other chronic health problems are not improving. Current approaches to address them view weight gain as the problem, rather than a symptom of poor metabolic health," it states on its website. So you could say it's a diet looking to address the root cause of these metabolic conditions.

According to Dr Amati, it would take years of glucose dysregulation to lead to a lot of weight gain, it's not an instant thing, she says. "Zoe helps you to regulate blood glucose and blood lipids, and improve your microbiome profile, all things that will help maintain your health long-term." 

Don't think that because you're not overweight, the Zoe diet has nothing to offer. Dr Amati has taken the test herself and says: "I'm in my 30s, I'm slim, I don't have any reason to be on a weight loss diet, but if continued eating the way that I was, not really thinking too much about my blood glucose levels, then the likelihood is that in 10 years time, I may have become overweight. My insulin levels would have been a little bit too high a lot of the time, which helps to store more fat, but it's a gradual process."

Food combining - how to minimise blood sugar spikes 

Zoe gives you an indication of how you metabolise carbs and fats compared to others of the same sex and similar age.

When Dr Armati took the test, her report showed that she was considered a good fat metaboliser, "but not a very good glucose metaboliser for my age." Does that mean she should cut out carbs because they spike her blood sugar? No, this is not about limiting food groups but hacking your personal metabolism. This is where clever food combining comes in. Zoe shows you that by combining foods you can help to buffer unwanted spikes, as Dr Amati explains:

"If I'm at a restaurant I'll often order a green salad or some vegetables first to slow the absorption of glucose into my bloodstream," says Dr Amati. "Fibre in the small intestine creates a coating that makes it more difficult for glucose to go straight into your bloodstream, so that’s a really easy way to reduce the impact of glucose. If I'm having a pizza, I'll always add to that pizza with some vegetables to make sure that I've had enough protein because otherwise I'm more likely to get hungry after because of the way my metabolism is set up."

"Equally, if you're peckish and you have a snack of a rice cake, for example, it’s always better to add to that with some peanut butter and chia seeds to make it a more balanced meal for your body. It’s always better to have nutritious, filling meals that have plenty of protein in them, as opposed to smaller incomplete meals as you're not really giving your body what it needs."

Zoe diet review: Science journalist and yoga teacher Vittoria D’Alessio, 54, puts it to the test

Why did I seek out the Zoe test? As a journalist, I have written a lot about the microbiome, and this has fuelled my interest in learning more about my own. I really do believe that a good deal of our overall health is determined by the mix of bugs in our gut. I was very curious to know what my gut was saying about me – and what I could do to improve the balance of microbes in my intestine to improve my energy levels. During lockdown, I often felt the pull of my bed for a post-lunch nap. I wanted to support my immune system and generally steel myself health-wise against developing future metabolic diseases.

When I put on weight earlier this year (I put on more than 6kg, which has never happened before) and the measures I would usually take to keep my weight stable - such as the high fat diet - failed to work. I became even keener to delve into the secrets of my gut.

The Zoe test aims to arm people with the information to both boost gut health, stabilise blood sugar and fat levels and examine how these elements work together to contribute to the way you process food. However, to be honest, I was less interested in learning about how my body reacted to sugars and fats. But as it turned out, the most interesting information from the Zoe testing came from this area.

Eating well is something I’ve given a lot of thought to for all of my adult life. Since my thirties, I’ve generally avoided white bread, pasta and rice wherever possible and gone easy on what I call ‘brown’ carbs (wholemeal anything). I’ve been keto on and off for the past five years, which I adapted to involve loads of veg. 

Looking back, I can see how restrictive the keto diet was and how much planning had to go into every meal. My mind was constantly on food – and the denial of it. My kids (now young adults) hated it when I went full-keto. They refused to believe it was good for me either on a physical or a psychological level. I can see that they were probably right. I was always tense around food and would jam my lips shut when one of them tried to pop a ‘treat’ into my mouth. Plus I’m half Italian and never eating pasta or risotto was hell! It was all a bit of a bore.

So I hoped that learning more about my microbiome and tweaking my diet to help it perform better through the Zoe programme might be a simple and healthy solution.

The results: is Zoe diet any good?

My results say that my microbiome is in good health. I have plenty of healthy bugs and my gut microbe diversity is in the top 25 per cent, hurrah! I would like to think this reflects the fact that I generally eat well and there’s plenty of diversity in the plant-based ingredients that I cram into my diet.

The results also show I have good blood fat control, meaning I process and eliminate fats well after a meal. I was horrified to find that my blood sugar control was poor, meaning it has a tendency to rise fast and high.

“The score we give you shows how you respond to a test muffin designed to trigger a blood-sugar response. But this is not how you generally eat and given your normal diet is a healthy one, I would use the score as an incentive to keep doing what you’re doing: keep eating healthily and consume things in their original matrix (whole food versus processed foods)," Dr Sarah Berry told me. “Our studies also find that nearly 50 per cent of your blood sugar response is predetermined by genetics.”

Dr Berry also says meal context is important: the time of day that you consume food, when and how much you exercise, and how much you’ve slept also contribute significantly to your blood sugar response. “A brisk walk after consuming a high-carb meal will reduce your glycaemic (bloody sugar) response. Eating carbs earlier in the day is best for most people.”

Post-test results: three months since I completed my Zoe diet test

Once your test results are in, the Zoe app switches modes and started educating me on the foods that are good for me. Using my personalised food scores that take into account my blood sugar control, it dishes up suggestions for foods that will help me manage my response and keep dietary inflammation at bay.

These foods also take into account the results of my microbiome test and the way my body responds to fats. The objective is to boost the diversity of healthy bacteria and keep me healthy. The app also suggests foods that combine well together to optimise my response.

The Zoe app puts great emphasis on plant diversity. You're encouraged to eat as much variety of fruit, veg and grains as you possibly can. It’s this diversity that feeds your microbiome and improves the make-up of healthy bugs living in your intestinal tract.

Before the test, I was chronically constipated and had been for much of my adult life. Since adapting my diet to fit the Zoe way, I’ve had no problems in that department and go to the loo at least once a day. It’s a radical change!

My energy levels have improved significantly since adapting my diet to the Zoe way, though I do still have days when I crawl under the duvet for an indulgent 15-minute afternoon nap.

I have not lost weight since doing the programme but neither have I put any on – despite enjoying a slice of sourdough or a bowl of pasta on a fairly regular basis. But I now know the reasons behind this weight gain. I have had a blood test and my hormones are out of whack, and my GP assures me this is responsible for my metabolism being out of balance.

My takeaway

Before doing the Zoe test, I was aware that the way I eat has a direct impact on the community of bacteria inhabiting my gut. What I hadn’t realised was that it’s not just my microbiome that’s unique to me but so is the way my body responds to dietary fats and sugars. I’m now fully on board with the idea that an undernourished microbiome along with blood sugar spikes and excessive fats in your blood can all trigger the body’s inflammatory response – something we want to keep in check.

I have learnt, from the Zoe education camp and from wearing the blood sugar sensor, that not all carbs cause massive spikes in my blood. If I combine carefully – say, a modest bowl of pasta heaped with a vegetable-based sauce – my bloody sugar barely registers a sugar hit.

I have loved switching my thinking from ‘carbs are bad’ to ‘diversity of plants is good'. I now eat tonnes of fruit and vegetables, placing emphasis on variety – I regularly stock my fridge with rainbow chard, cavolo nero and pomegranates, ingredients I’ve always loved but not really bothered with on a regular basis. Best of all, I’ve introduced ‘sweet’ foods like grapes, melon and figs, because their sugar content is not their only defining feature – they are also packed with nutrients that the bugs in my gut will thank me for introducing. I eat pasta from time to time (still wholemeal or spelt) and there is no guilt. I get a lot more pleasure from eating since doing the Zoe test because I spend zero time obsessing about what I shouldn’t eat. Nothing is off the menu. My Zoe scores simply make it easier for me to make better choices more often.

The Zoe app gives food scores that help me make my choices. A ‘super green food’ gets a score of 100, meaning I’m free to enjoy it at will. A low-scoring food (0-24 out of 100) means ‘only take this once in a while.’ A doughnut would fit into this category. Foods with middling scores (bread is most likely to sit in this category) are there to be enjoyed in moderation. All scores are based on my unique microbiome and my personal response to sugars and fats.

I do feel a lot more in control of my diet in a positive way now. Eating has become more joyful, my food is enjoyed more freely without the guilt that was ever present in my keto days. Tonight I’m making (wholemeal) spaghetti with mussels, something I would never have permitted myself on the keto diet. The very thought fills me with guilt-free joy. I’m finding meals tastier and more satisfying. I see this as a ‘forever’ lifestyle change. My dietary concerns now are about adding plant variety to my diet and balancing carbs with greens. The effort is minimal and the satisfaction I’m getting from my meals is so much greater than it was when I was tying myself into a pretzel over getting enough fat down my throat.

Sign up for the Zoe Nutrition Programme here