Dr Michael Mosley is a science presenter, journalist and television producer, who has worked for the BBC for over 30 years. He is also a best-selling author, having published a variety of diet and health-orientated books, including The Clever Guts Diet, The Fast Diet, Fast Exercise, and The 8-Week Blood Sugar Diet.
Dr Mosley’s diagnosis of type 2 diabetes in 2012 sparked the 8-Week Blood Sugar Diet, which aims to combat high blood sugar levels and, in some cases, reverse type 2 diabetes.
We recently caught up with Michael to have a chat with him about his work. Here’s a transcript from that interview.
What is your journey with diabetes? How did you combat it? Did you immediately turn to rapid weightloss or was it something you discovered worked over time?
Back in March 2012, I went to see my GP for a skin complaint and I had a blood test. She contacted me later to say my blood sugar was high. We had some repeat tests and she broke the news that I have type 2 diabetes and I had to start on medication. I was referred to the diabetes nurse and then we saw how the treatment went. I wasn’t very keen because my dad had type 2 diabetes and he died from complications of diabetes at about the age I was when I was diagnosed. This made me think there must be something better than medication and that’s when I started looking into intermittent fasting. I persuaded the BBC into letting me make a documentary called “Eat Fast Live Longer”.
I went to America and met experts and I came up with the idea of the 5:2 where you cut your calories a couple of days a week and I lost about nine kilograms in about eight weeks of doing that. My blood sugar went back entirely to normal. I thought that was pretty exciting and interesting. I wrote a book with journalist Mimi Spencer called the “Fast Diet” which was kind of about the 5:2 diet, other forms of intermittent fasting and the health benefits that could appear from doing that. That was in 2013 and I haven’t looked back.
Could you explain the Fast 800, the process and the reason behind why it works?
The Fast 800 is the latest iteration of what I’ve learnt because I’ve also written a book called “Fast Exercise”. I was interested in finding out why I’d managed to reverse my diabetes because I was told at the time that it was impossible – it was a progressive disease. So, I met up with Professor Roy Taylor of Newcastle University and he said it’s because I lost a lot of weight fast. I’d lost about 10% of my body weight and he’s done these studies that showed if you are a bit overweight, you have type 2 diabetes or pre-diabetes, you lose about 10% of your body weight then that unclogs your liver and your pancreas, which have got stuffed with fat and that seems to be enough to return them to functioning normally again. He was doing a big trial at the time looking at doing 800 calories a day every day for up to 20 weeks. The Fast 800 was born out of that because I’d started with the 5:2 and nowadays, I have the website fast800.com and we suggest rapid weight loss on 800-900 calories per day. You do that for up to 12 weeks, in which time you will have lost a lot of weight.
Typically, people lose something like 10kg, about 22-23 pounds over that time. If you have type 2 diabetes then, obviously, you must talk to your doctor before starting. Certainly what Professor Taylor’s studies have shown was that around half of the people who went on this rapid weight loss diet lost an average of around 10 or 11 kilos and around half of them were able to come off all or some medication. he’s been following them now for nearly three years and the majority have managed to keep the weight off and they are still off medication. In fact, he had a control group who followed standard advice and they’re becoming much sicker over time whereas the group who lost the weight are staying remarkably healthy, are much happier and on much lower levels of medication.
The primary idea is you start with rapid weight loss, 800-1000 calories a day, we provide all of the recipes and things like that. You start increasing your exercise activity, then when you’ve done that, we recommend that you stick to it for at least three to four weeks. You might move on to the 5:2, where you’re just doing it a couple of days a week and eating healthily the other days. Then you move on to what we call the “way of life”. The programme includes a support group and lots of medical support for people who need it. Losing weight is tough, keeping it off is also very tough, but we’ve got some really good statistics coming out of it. It’s a kind of graded programme, you start fast, then you go to a more gradual weight loss and then you have the way of life, which keeps you going.
One of the follow-up questions was going to be about maintenance, but you mentioned the support group and that must be a massive help?
The thing that is completely critical if you want to maintain the weight loss is having a support group. The way you lose weight in the first place is also important as you need to preserve your metabolic rate. That’s why the type of diet I’m recommending, the evidence from the clinical trials is that people’s metabolic rate does slow down a bit, but only in line with what you would expect. If you are 10kg lighter, you’re going to be carrying 10kg less around and then your metabolic rate is going to be a little bit slower.
What we found with our dietary approach is that you don’t lose more than that. You’re back to where you’d be if you’d gone down from 14 stone to 12 stone, your metabolic rate is that of someone who has always been 12 stone. You don’t get a deficit, which is one of the big fears and is seen in some other types of diet. You must eat decent amounts of protein. We do have to emphasise the importance of protein on the Fast 800 because you need to preserve your muscle and we recommend increasing your activity. Again, to keep your metabolic rate up.
Beyond that, it’s about the support group and also about regularly measuring yourself, whether it’s your weight or your waist. These seem to be the most important things. There is a myth out there that 95% of diets fail. It’s sort of true because 100% of bad diets fail, but proper ones, the track record is very good. The biggest, longest weight loss study in the world was one that ran for 10 years and they found that about a quarter of the people were able to sustain a weight loss of over 10kg, which is more than 22 pounds. Over half of them managed to maintain a weight loss of over 5kg. If it’s done properly, you absolutely can keep it off and even if you do put some, or indeed, all of the weight back on, you will have the benefit of all the years without it.
Why do you feel the slow and steady approach to losing weight isn’t as effective as people think?
It’s just because that’s what all the clinical trials show. There has been a whole load of them recently, the idea of some science is you do clinical trials to try and prove or disprove a hypothesis. The theory has been for a long time that it’s better to go slow and steady, although there’s never been any good evidence that is true. We’ve seen four or five big clinical trials with large groups of people run in different centres in the UK, Australia and also the Middle East. They have all consistently shown that if you take the 800-calorie approach then you lose more, you keep more off you’ll see more health benefits than the group who are allocated to the slow and steady.
There are psychological reasons, one of which is that people find it difficult when they’re not seeing improvement. Whereas, when you’re seeing rapid improvement, you’re much more motivated to stick to it. As I said, what the studies have shown is contrary to what you and I have always been told – slow and steady does not win the race. It’s not suitable for everyone and it’s worth visiting our website to check out who it’s suitable for.
The clinical trials certainly suggest that in suitable people, it’s much, much more effective than slow and steady. In all the long-term trials, where they look at people over 5 to 10 years, the best predictor of how much weight you will lose over 5 to 10 years is the amount of weight you lose in the first month of the diet. That’s what the science says. I’m still bamboozled by the fact people keep on telling me that slow and steady is so much better when there is no true evidence. The reason why so many diets fail is that people give them up. People are much more likely, and that’s what they’ve found in clinical trials, to give up if they’re in the slow and steady group because they get dissatisfied with the very slow rate of progress. Some people it suits great, but most people, it appears, would do better in a more accelerated programme.
A slow and steady approach has always been here, is this the first diet that has challenged it?
I think so because slow and steady just makes sense, doesn’t it? It makes sense to want to do things gradually with everything in moderation. The thing is, we know that people like everything in moderation but, people’s idea of moderation depends on what they’re doing at the moment. Your idea of what is a moderate meal would be completely different to mine. Yours might be a large pizza and a can of coke. It means nothing at all.
What is fascinating about these studies is there’s so many of them and they all consistently point in the same direction. There was another one, “5000 people with pre-diabetes”. Again, they were randomly allocated to either rapid weight loss or slow and steady. They were followed for five years and, again, it was the group who had done the rapid weight loss who were so much healthier at the end of their time. It’s not just about weight, it’s about health. What’s your blood pressure like? What’s your blood sugar like? What’s your cholesterol score like?
I do suggest that once you’ve lost the weight you move on to a Mediterranean-style diet. That’s something which is full of healthy fats, plenty of protein and lots of vegetables. You don’t stay on it forever, the idea is that you stay on it for up to 12-weeks in a clinical setting where you’re being properly monitored by doctors and then if it benefits you, you can do at least 20-weeks. Some people have done it for longer.
If you’re doing an online programme, I would say 12 weeks is a decent period and at any point, you can switch over to what I’d call the “way of life” – that’s based around a relatively low-carb healthy, Mediterranean-style diet. We know that’s the healthiest diet on the planet. It is also the one that people seem most likely to stick to. I’ve looked at some really interesting studies where they did low-fat, low-carb or the Med diet over seven years. Although the low-carb group did the best in the first year, at the end of seven years they’d put almost all the weight back on as had the low-fat group. The people on the Med diet had managed to keep it off and sustain around 5kg. That is pretty good going.
Over that period, most people would be putting on about 5kg, because we typically put on about half a kilo in the ages between 30 and 50. They were effectively 10kg down from what you would expect. That’s another thing that’s worth considering in these weight-loss trials; it’s not just whether you go back to the weight you were, but you will already be further down than your friends and neighbours because, typically, between the ages 30-55 we put on about half a kilo a year.
What makes the Mediterranean-style diet so effective?
There is so much evidence and so many studies now showing its benefits. Broadly speaking, it’s one where you eat oily fish a few days a week and you have plenty of olive oil splashed on things. Olive oil is anti-inflammatory, plus the fat will keep you full, and it tastes delicious, with plenty of veg and legumes. We all know about veg and fruit, but legumes get a bit left out – they’re things like lentils and kidney beans. They’re high in fibre, satiating and they’re full of all sorts of nutrients. Much more so than rice, potatoes and the things we typically go for.
Med-style has modest amounts of dairy and some meat in it, but the meat content is considerably less than that of your average European diet. Less processed food as it’s oily and ultra-processed food is fattening stuff, it’s all the junk food, the fast food. Those are the things that make you go insanely hungry and they also cause inflammation. That’s another thing about the Med diet, it’s an anti-inflammatory diet.
We’re already beginning to recognise it has benefits for your microbiome; it has bacteria, which has a big impact on your sleep. It’s all about the different systems in your body – sleep, exercise, your weight and your stress levels are all intimately tied up with each other and with what’s going on in your gut; your microbiome. All these things play into each other and together, if we get them right, that’s when you are at your healthiest.
Any advice for people who worry they’ll feel constantly hungry on the Fast 800 diet?
When I wrote the original book, it was mainly based on animal studies because there were relatively few human studies at the time. The researchers were saying that a quarter of the normal number of calories that you would eat would provide results and that was based largely on rats. For humans, that equated roughly to 500-600 calories, so that’s what I wrote about.
Since then, the evidence seems to be that you get similar effects for eating 800-900 calories, making it more sustainable and people find that easier to stick to. It still produces a significant calorie deficit, but it’s much easier in the long term. What we’ve found, and what Professor Taylor found in his study, is that if you eat the right food, that is rich in fibre with plenty of protein, then it’s a challenge for the first week. As time goes on people stop feeling hungry, they stop feeling the same crazy cravings they’ve had and they adapt.
That also reflects our ancient past when we were cavemen and women, we wouldn’t have had ready access to food all of the time. It would have been very distracting to be crazily hungry all the time, so it makes sense that your body is designed to switch off the hunger mechanism. A lot of the hunger we feel is triggered by our high sugar, high junk food diet we have and that’s really what drives cravings. When you move onto a much healthier diet, you’ll find it will surprise you how rapidly you get comfortable with it.
How long do you say it normally takes for people to adapt?
For some people, it’s two or three days and for others, it can be two or three weeks. It’s variable, but broadly within that range. I would expect within the first week you would start to adapt. By the end of the second week, you would start to feel quite good on it.
People report feeling more mentally alert and by then you’ll be in a state of Ketosis, where your body is producing these Ketone bodies and your brain seems to quite like that. People do report increased sharpness, increased mood – they feel better on it and these are not things you would expect when you are cutting your calories. You don’t have that same sort of soggy, saggy feeling that often goes with eating too much junk food. You’ll be sleeping better as well and that also will play into your mood.
Is the Fast 800 diet aimed only at those concerned about diabetes or can anyone use it to their advantage? Are there any other groups of people that you’ve come across who might benefit from it?
Broadly speaking, this is mainly suitable for people who are overweight or obese, particularly people who have other issues like raised blood sugar levels, they might be pre-diabetic, they might be diabetic or who have high blood pressure.
If you’re on medication then it is advised you talk to your doctor because one of the things is when you go on this diet your blood sugar will come down rapidly and you are in danger of being over medicated. We also do suggest it’s only really suitable for people over the age of 18. I wouldn’t recommend it for people who have previously struggled with eating disorders.
In most other groups, if you’re in reasonable health, you can get on with it. I do recommend you kick on for a couple of weeks and if you feel terrible doing it, then go to something gentler like the 5:2, where your calories are cut just twice a week.
What exercise regimes would you recommend to supplement the diet?
I wouldn’t recommend you take up the marathon! If you already run long distance then there’s no reason why you shouldn’t continue. You will begin to burn fat much faster. After all, the whole point is you want to get into the state where you’re burning fat and most of us have enough fat on us to last for at least six to nine months.
If people are worried about their blood sugars falling, you have quite a big store of sugar in your muscles and liver in the form of glycogen, but you have this massive store of energy in the form of fat. If you’re not active at the moment then I do recommend you increase very gradually – brisk walks first thing in the morning, try and do at least 100 paces a minute. Increase that to a bit of jogging – there are lots of good apps like the NHS Couch to 5K, which will take you through the process.
We also have the online course, which we provide at the Fast 800, that takes you gradually through increasing levels of activity. I’m a fan of HIIT and that can be on a bike or running. I live at the top of some hills, so I do little sprints up the hill, short 30 second bursts. When I’m out walking, I put up the pace.
It’s also important to do strength exercises, so I do a workout when I get out of bed first thing in the morning, which combines things like squats, press-ups and lunges. I do five minutes of that most mornings and that keeps the muscles toned. On top of that, I do exercises to improve my balance. Those are the three key things; aerobic exercise to help with cardiovascular endurance, resistance exercise to keep the muscles in shape and a few balance exercises.
As you get older, you’re more at risk of accelerating muscle and strength loss, so why is the diet not a risk for older people?
You must keep up the protein. We also have meal replacement shakes and they’re all based on delivering at least 60 grams of protein a day. It’s not the deficit in calories that causes the problem per se, it is the protein deficit. The problem with some of the old rapid weight loss diets in the 60s and 70s is that if you don’t have enough protein in your diet then you will lose muscle mass. This one is based very much on making sure you get enough protein.
Professor Roy Taylor in his studies measured using MRI. He looked at the levels of the volunteers and they managed to lose 10kg without losing large amounts of muscle. I do think you have to keep up the protein and maybe increase it a bit. The quality of the protein is also important.
It’s difficult to do this diet if you’re a vegan, in fact, it’s probably impossible. Unfortunately, vegans struggle to get enough protein in their diet. It mainly comes from things like nuts and legumes, you’d have to consume a lot of those to get enough. You can switch to a vegetarian diet, but it is easier if you’re an omnivore because meat and fish are very rich sources of protein. We do also provide vegan shakes if you want to do it that way, but I would emphasise again and again, it’s really important whatever your age, but particularly as you get older, that you’re consuming enough high-quality protein.
What would your advice be to the people who won’t be able to significantly alter their lifestyle to achieve rapid weight loss?
We know that you don’t have to lose 10%. That is a figure to aim at if you have type 2 diabetes. Losing 5% of your body fat also produces very meaningful change. So if you’re currently 80kg, that means losing 4kg and I think that’s a manageable figure. 4kg will translate into about 4cm off the waist. Broadly speaking, for every kilogram you lose, about a centimetre is also lost.
Beyond that, just a healthy lifestyle – a low-carb, Med-style diet will be good for your life. Making sure you are getting in at least half an hour a day brisk walking first thing in the morning, trying to do some of those press-ups and squats. Going for a run if you feel the urge to do so.
Prioritising sleep is important. That is tricky, particularly as you get older because your sleep tends to fall off. I also wrote a book called “Fast Asleep”, which is all about the science of sleep and how to get a good night sleep because there are lots of tricks. Most of the obvious one’s people know about, like a dark, cool room. I go into a lot of the less obvious ones. I’m a bit of an insomniac, so I’ve tried them all myself. Sleep is incredibly important.
As I said, the main components of maintaining a healthy life and weight include a decent amount of activity, sleeping well and also managing your stress. For stress I would advocate mindfulness, there are plenty of apps like Calm or Headspace. If you’ve never tried mindfulness, it is worth giving it a go. It doesn’t suit everyone, but it does seem to be a good way of reducing stress. Spending time in green spaces, going down to the woods, going for a walk – those things are all really good for managing stress. Chatting to your friends, something that’s been hard to do in recent times, they’re all important as well. Stress management is a key part of the Fast 800 programme.
What changes would you like to see in the food industry as it currently stands and what steps do you feel need to be taken to combat the health issues that are prevalent right now?
There are three categories of food if you like: there are natural foods, like a piece of meat, a bit of fish, an apple or something like that. There are processed foods, which includes things like yoghurt and cheese. Then there are ultra-processed foods and those are the things that you buy in supermarkets that are in packages and have all different kinds of ingredients in them. They owe more to the petrol chemical industry than they do to anything else. Those are the foods that we find very hard to stop eating. They have been carefully engineered to make you go on and on eating them – they’re the unhealthy ones, the ones that will put on the fat.
What I would like to see is very much like the war with tobacco. We are in a position now where food processing companies, particularly the ones that produce ultra-processed foods, make huge amounts of money and they’re going to defend their industry to the death. They create pseudoscientific organisations that spew out nonsense research. Interestingly, one of the things they like to emphasise is exercise, which is one of the reasons why companies like Coca-Cola sponsor the Olympics, because of the emphasis on exercise. It takes the emphasis away from what you’re eating and from what you’re doing. I’m a big fan of exercise, but it’s not a good way of losing weight or keeping it off.
I do think the sugar tax was a step in the right direction, but just like the war on tobacco, the war on ultra-processed food is going to require huge political wealth and is going to require a multi-faceted approach. With tobacco, first of all, it was recognising the problem and sticking tax on it. Then there was limiting advertising and making it socially unacceptable, make it harder to smoke indoors, make it impossible to smoke in pubs. It was a very gradual process; it took 40-50 years.
Amsterdam is the only city on Earth where they have managed to reverse the rising tide of obesity in children. They did it through a whole range of foods, including quite Draconian measures, like banning children from bringing unhealthy food and drink into schools. They also sent people out into the communities to teach parents what healthy food looks like, to teach them how to cook because, unfortunately, we’ve lost that ability, so people go out and buy junk food. We subsidise junk food, so the constituents of it are generally corn-based. The UK, USA and the European Union have traditionally subsided these foods, which is why they are so cheap. They tend to be low in protein as it is expensive, and high in sugar and fats, which are cheap. The profits are huge and the cost is not born by the manufacturers, they’re born by us consumers. I think it’s going to be a long, hard struggle to see change, but I remain optimistic.
Do you think we will get there in the end?
I think we’ll have to because we’re seeing rising tides of obesity. It’s like smoking, at some point the Government looked at it and it shocked them how expensive it was. Even the figures you see are much worse than what’s published. For example, the often-quoted figure is that 60% of adults in the UK are overweight or obese. That includes 20 to 30-year-olds, who are generally not that fat. 78% of men over the age of 50 are overweight or obese. As we get older, we get fatter.
It’s been estimated that type 2 diabetes, which is very much related to central obesity, the cost of that is somewhere around £20-£25 billion a year in terms of indirect health cost, including the cost from early retirement and sickness pay. We are spending a humungous amount of money and those numbers are only going to increase as we get older and fatter. There is no evidence of obesity slowing down, if anything it’s still going up. The latest prediction I saw is currently a third of adults, and that includes the 20 to 30-year-olds, are obese and that figure’s predicted to double possibly in the next 20 years.
Boris Johnson said the reason he became so sick and nearly died with COVID was that he was one of the fatty’s and that was at least an honest acknowledgement. I think one of the things COVID has done is made people appreciate in the immediate here and now the threat of central obesity. My wife is a GP, she sees patients and brings it up with them. Again, GPs are very reluctant to talk about it and then she asks them if they’re concerned or thinking about it. If they say “no” then she doesn’t follow it up. If they say “yes”, then that’s how the conversation begins. GPs are very reluctant to bring up the subject because they don’t want to show prejudice against overweight people, but it has to come from somewhere.
You get no training at medical school on the biggest problem of our time, which is obesity and how to talk to patients who are overweight or what to do for them. That plays no part in the medical curriculum, which is insane. All you do is treat the diseases which are associated with obesity and being overweight. You’re taught how to treat diabetes with medication. A lot of cancers are driven by central obesity. Obesity has now overtaken smoking as the leading cause of death in the UK and it’s not just death, it’s all the other things, like dementia and heart disease, that come with it. The average person is already on some life-limiting illness by the age of 64, they’re already on medication, so they lead the next 20-years of their life in ill health. Who wants to do that when you can avoid it?
It’s not just about extending your life, mainly, it’s about extending your healthy life. If you’ve ever seen a smoker who’s in their 60s, they look terrible, they feel terrible, they’re depressed and they wonder why they ever did that. It’s not just how long you live, it’s about your quality of life. Get going now with making a healthy change. Signs of dementia start to occur in your 40s. In your 30s and 40s, you’re starting to lay down the problems, which will come and bite you sooner than you think.
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