One of the great things about The Fast 800 is its flexibility – you can tailor this diet to suit your needs, goals and motivation. There are three stages to this diet: The Very Fast 800, The New 5:2 and The Way of Life. All our recipes are based on a moderately low carb Mediterranean style diet – regularly cited by health professionals as the healthiest diet in the world.
The rapid weight loss stage of the diet involves eating 800 calories a day. If you decide this approach is for you, we recommend that you stay on this stage for a minimum of 2 weeks, though you can stay on the plan for up to 12 weeks depending on your goals and how much weight you have to lose.
To most people 800 calories doesn’t sound like a lot, and that is why we have based the 800 calorie a day meal plans in the online programme on delicious Mediterranean style diet recipes, which are designed to keep you feeling full and satiated.
The Very Fast 800 involves rapid weight loss. It is also a highly effective way to bring down raised blood sugars (i.e. pre-diabetic or type 2 diabetic). Over the past few years major studies have shown that following an 800 calorie a day diet is much more effective than going “slow and steady”, with typical weight loss of around 10kg. Rapid weight loss is also the best proven way to reverse type 2 diabetes and prevent people with pre-diabetes from becoming diabetic.
Because The Very Fast 800 is an intensive approach to weight loss, it is not suited to everybody. As with any diet, you should speak to your usual health professional before commencing The Very Fast 800 approach, and please see our medical disclaimer for information regarding cautions and exclusions as to who shouldn’t do the diet. If you find that this approach isn’t for you, you can skip straight ahead to The New 5:2 plan or the Way of Life.
1. Burning fat by flipping the metabolic switch
Your body is like a hybrid car; it runs on two different fuels – sugar and fat. When your body needs a quick burst of energy, the first fuel source it turns to is the glucose (sugar) in your blood. Next it will draw on the sugar stored in your liver and muscle (glycogen). Only when this starts to run low does the body turn to its fat stores. Your body can’t just burn fat. Instead it turns some of your fat stores into ketone bodies, which its uses as energy. The buildup of ketones in your blood is called “ketosis”.
When you are on a low calorie diet (800 calories a day) you will begin to rapidly use up your fat stores. The first fat to go will be that around your gut, the visceral fat. This is also the most unhealthy fat. Because The Very Fast 800 plan is also moderately low in carbohydrates, this will add to the fat burning.
People worry about running out of energy on a low calorie diet, but the reality is that most of us have such big fat stores we could go for months without eating. The reason you may feel hungry and perhaps more tired than usual for the first week that you are on the diet is because your body is having to adapt to running on a different fuel, fat. But you should soon start to feel better – more energetic and clearer thinking.
2. Improve your insulin resistance: stop snacking and watch the hunger disappear
We are often told that we should snack between meals to avoid getting hungry. There are two serious problems with this advice. Firstly, the more often people eat, the more they eat overall. And secondly, if you are snacking all the time that means you constantly have lots of sugar circulating in your blood. Constantly topping up your blood sugars is a really bad idea.
The reason you don’t want to keep you blood sugars topped up is that having high levels of sugar in your blood damages your arteries and nerves. Sugar, in high concentrations, is toxic to the cells. So, after a sugary, carby meal your pancreas produces lots of insulin to bring your blood sugar levels down. Unless you go for a run, to use that sugar up, most of those excess calories will get stored as fat.
And it gets worse. Because if you have lots of snacks and sugary treats then your pancreas needs to produce more and more insulin to bring those blood sugars down. It is like shouting at the kids. After a while they stop listening. The same is true of your body; over time you become insulin resistant. When the pancreas can no-longer produce enough insulin to keep your blood sugars in check then you will be on the downward journey to pre-diabetes and eventually diabetes (where the pancreas just packs up).
The good news is that an 800 calorie diet is a highly effective way to lose weight and reduce insulin resistance.
The Very Fast 800 plan uses Mediterranean-style ingredients to keep you feeling fuller for longer. We also recommend that you take a multivitamin whilst following this plan to guarantee you are getting all the necessary nutrients and vitamins. If you join our online programme we provide you with delicious meal plans so you don’t have to worry about counting calories.
You may also want to use shakes for those busy days when cooking just becomes too difficult. We have developed The Fast 800 shakes to reflect the quality of our nutritionist-designed meal plans. Low in sugar and based on all natural ingredients, they are designed to fit perfectly alongside the rest of The Fast 800 plan, They deliver an exact balance of vitamins, minerals, protein, fibre and probiotics.
It is also extremely important to stay hydrated when following this plan. As a guide, try to take in at least 8 cups a day, or about 2 litres. The commonest side effects of going on a rapid weight loss diet are headaches and constipation, both of which can be prevented by drinking lots of water. One other possible complication of rapid weight loss is gallstones, though gallstones are also very common in people who have diabetes or are overweight.
The DiRECT trial (2018) (1)
The DiRECT trial is a ground breaking study carried out in the UK involving nearly 300 overweight type 2 diabetics. The participants were randomly allocated to either a 800 calorie diet for 12 weeks, or to a standard diet. The participants on the 800 calorie diet made a gradual return to a more normal diet after the 12 weeks of 800 calories. Both groups were then followed for two years.
The results in the rapid weight loss group were astounding. Average weight loss was 10.5kg and nearly ¼ lost over 15kg. Even better, nearly half of them got their blood sugars back to normal despite not being on medication. Two years on and those in the rapid weight loss group are still going strong.
The DROPLET trial (2018) (2)
This was an 800 calorie trial, carried out by researchers from Oxford University with overweight patients and followed for a year. Average weight loss at the end of a year was again 10kg, with the 800 calorie group showing big improvements in blood pressure, cholesterol and improvements in biomarkers of cardiovascular and metabolic risk compared to the control group.
Following the success of DiRECT and DROPLET, the NHS is proposing to allow GPs to consider prescribing a very low calorie diet to patients with a high BMI.
The PREVIEW study (3)
The PREVIEW lifestyle intervention study is, to date, the largest, multinational study aimed at preventing type 2 diabetes. 2,326 pre-diabetic patients from eight countries followed an 800 calorie diet for eight weeks as part of a longer term weight loss management and diabetes prevention study.
After eight weeks, participants had lost an average of 11kg, and experienced an average reduction of 10cm in waist size.
Intermittent fasting is a highly effective way not just to lose weight, but to build a healthier, brain and body.
This is why, after you have completed The Very Fast 800 stage, we recommend The New 5:2. Instead of keeping to 800 calories per day every day, you schedule two days a week as 800-calorie “fasting days”, and follow a healthy Mediterranean-style diet for the rest of the week. You can also jump straight to The New 5:2 if you find that your goals and needs are better suited to this approach.
On your fast days, your body will enter a state of ketosis, just as it would on The Very Fast 800 phase. You will lose visceral fat and achieve a better response to insulin. This, in turn, will make it easier for you to keep to sensible portions during the rest of the week.
Fasting for two days out of seven also gives you a chance to experience the other benefits of fasting, which include:
Intermittent fasting involves restricting calories to 800 a day on fasting days, then eating a healthy lower-carb Mediterranean diet for the rest of the time.
The beauty of intermittent fasting means that as your insulin sensitivity returns, you will feel fuller for longer on smaller portions. This is why, on non-fasting days, you do not have to count calories. By maintaining a Mediterranean-style diet, you will take in all of the healthy fats, protein, fibre and fresh plant-based food that your body needs, and no more.
If you join the online programme we provide you with 5:2 meal plans which provide you with delicious Mediterranean style recipes for both fasting and non-fasting days. You might also find The Fast 800 shakes useful for your fasting days.
Please note The New 5:2 is not suitable for everyone, and we always recommend consulting your usual healthcare professional before beginning any diet or fitness regime. If you find that this approach isn’t for you, you can skip straight ahead to the Way of Life plan.
A rapidly-growing body of studies demonstrates the benefits of intermittent fasting.
In a study carried out in 2013 (4), 115 overweight women, aged 20 and 69 and with a family history of breast cancer, were randomly allocated into three groups:
After three months, the women on the 5:2 diets had lost an average of 4.2kgs, 3.6kg of which was fat. This was twice as much as the full-time dieters, who had lost an average of 2kg of fat.
Insulin resistance had also improved significantly in the two-day diet group, which did not happen with those on the standard diet. Those who stuck with the 5:2 diets for six months lost an average of 7.7kg and three inches from their waists. Some lost over 20kg.
Another study by researchers at the University of Surrey examined the impact of the 5:2 diet on the body’s ability to metabolise and clear fat and glucose after a meal on 27 participants. (5)
Those on the 5:2 achieved 5% weight loss in 59 days compared to 73 days by those on the calorie restriction diet. Results also showed that:
What is it?
The Way of Life phase is a structured, nutritionally-balanced guide to eating a healthy Mediterranean-style diet for life.
Who is it for?
How you maintain your results on The Fast 800 is very much a personal choice. For most people it is safe to continue with The New 5:2 diet long-term, and many people find that this is an excellent way to stay healthy.
Other people prefer to move onto the Way of Life phase, which doesn’t involve calorie counting, just portion control. To safeguard against a return to previous habits, the online programme guides you through the Way of Life phase, giving you support not just with meal and recipe planning, but with staying fit and coping mentally with the tougher times. You can also stay motivated with the help of our busy forum, where you can share tips and tricks with others who, like you, have managed to achieve successful weight loss.
If you don’t want to try The Very Fast 800 plan or The New 5:2 plan, or find that these plans aren’t suitable for you, you can always jump straight ahead to the Way of Life phase.
Why it works
People tend to eat the wrong foods because it feels right to do so. When you bite down into a muffin or dive into a packet of crisps, you are responding to carefully-designed cues, put in place by food manufacturers, to use food as a defence not just against hunger, but against stress.
The Mediterranean-style diet tackles this problem at its root. Based on the diet that has been enjoyed for centuries by people living in and around Southern Europe, it is free from added sugar and refined carbohydrates, and instead uses ingredients that have been scientifically proven to make you feel good:
How to do it
By using our meal plans, you can plan for, shop and prepare the week’s food with minimum fuss. Our recipes are designed to be low on effort and high on flavour, and can often be prepared in double quantities to be packed up the next day for a lunch on the go.
If you’re really pressed for time, or are going to be out and about for the day, [The Fast 800 shakes] are designed to work within the Way of Life phase as an optional feature, and are formulated with whole-food ingredients such as coconut and almond flour, and natural vanilla flavouring.
Another optional feature of The Fast 800 is the practice of Time-Restricted Eating (TRE). Pioneered by Dr Satchin Panda of the world-renowned Salk Institute in San Diego, TRE allows you to capture the benefits of fasting without restricting the amount of food that you eat.
Instead of limiting your calories, TRE limits the period during which you eat to 12, 10 or 8 hours, including overnight sleep-time. This allows the body sufficient “down time” from the work of metabolising food to engage deep-level tissue repair processes, especially the clearance of non-optimal cells, also known as “autophagy”.
The good news is that the longer you stick to this maintenance phase, the easier and more natural it becomes. Behaviour change is linked to reward, and the nutrient-rich Mediterranean-style diet delivers visible results from day one.
The evidence
Since the 1970s, scientific evidence displaying the wide-ranging benefits of the Mediterranean-style diet has accumulated. One of the most wide-ranging and in-depth studies, conducted in 2008 by the University of Florence, reviewed the findings of 12 studies, together following 1.5m people. (6)
It found that those following a Mediterranean diet were 9% less likely to die young, and also less likely overall to die of heart disease, stroke or cancer. They were also less likely to develop Parkinson’s disease or Alzheimer’s.
Another study showcasing the benefits of the Mediterranean diet is the PREDIMED study. The PREDIMED study involved a large randomised trial of 7,447 individuals, who were at high risk of cardiovascular disease (7). Participants were randomised to a Mediterranean diet supplemented with either nuts or extra virgin olive oil, or to a low-fat control group. The effects of the diet after more than 5 years’ observation were then investigated.
A large number of papers have been published on this trial, and the key results are summarised below:
The Fast 800 is an innovative approach to healthy living based on the latest scientific research in the area of health. The programme is based on Michael Mosley’s best selling books – ‘The Fast 800’, ‘The Fast Diet’, ‘Fast Exercise’ and ‘The Blood Sugar Diet’. Any advice given is not meant as a substitute for care by your usual health professional, who should be consulted for any medical conditions.
* Results may vary from person to person.
This site uses cookies. By continuing to browse the site, you are agreeing to our use of cookies.
OKLearn moreWe may request cookies to be set on your device. We use cookies to let us know when you visit our websites, how you interact with us, to enrich your user experience, and to customize your relationship with our website.
Click on the different category headings to find out more. You can also change some of your preferences. Note that blocking some types of cookies may impact your experience on our websites and the services we are able to offer.
These cookies are strictly necessary to provide you with services available through our website and to use some of its features.
Because these cookies are strictly necessary to deliver the website, refuseing them will have impact how our site functions. You always can block or delete cookies by changing your browser settings and force blocking all cookies on this website. But this will always prompt you to accept/refuse cookies when revisiting our site.
We fully respect if you want to refuse cookies but to avoid asking you again and again kindly allow us to store a cookie for that. You are free to opt out any time or opt in for other cookies to get a better experience. If you refuse cookies we will remove all set cookies in our domain.
We provide you with a list of stored cookies on your computer in our domain so you can check what we stored. Due to security reasons we are not able to show or modify cookies from other domains. You can check these in your browser security settings.
We also use different external services like Google Webfonts, Google Maps, and external Video providers. Since these providers may collect personal data like your IP address we allow you to block them here. Please be aware that this might heavily reduce the functionality and appearance of our site. Changes will take effect once you reload the page.
Google Webfont Settings:
Google Map Settings:
Vimeo and Youtube video embeds:
You can read about our cookies and privacy settings in detail on our Privacy Policy Page.
