• Dr Emma Derbyshire

The New Fast 800 Diet: Turning the Tide on Type 2 Diabetes

The Fast 800 is a novel approach to healthy living, which is based on Dr Michael Mosley’s best-selling books: ‘The Fast Diet’, ‘Fast Exercise’ and ‘The Blood Sugar Diet’. The Fast 800 was developed by a group of doctors, nutritionists and lifestyle specialists, which aims to help patients lose weight and improve their health with a novel rapid weight loss programme. The Fast 800 is not one diet but several different approaches that are tailored to the patients’ particular aims, be that controlling blood sugars, losing a little weight, or losing significant weight. The Fast 800 brings together a number of core areas: intermittent fasting, a Mediterranean style diet, and exercise and mindfulness.

What Does the Fast 800 Diet Involve?

The Fast 800 has been designed as a flexible plan, which most importantly is designed to be sustainable as a lifestyle choice. The Fast 800 can involve several stages, from rapid weight loss at the beginning, through to sustainable intermittent fasting. The Fast 800 is a 12-week digital lifestyle programme, launched in parallel with Dr Michael Mosley’s book, which offers a tailored approach to food and exercise, based on an individual’s personal online assessment. The Fast 800 programme includes personalised menus, as well as a detailed programme of exercise and mindfulness, the programme has tools designed to support habit change and help people establish a sustainable and healthy lifestyle. Key to this is a community sharing the journey with coaches offering guidance and support.

Stage 1: The Very Fast 800: Rapid Weight Loss

  1. Those with a lot of weight to lose begin with the Rapid Weight Loss stage of the diet. This involves 800 calories a day.

  2. This stage can last for between 2-12 weeks, depending on circumstances and how much weight loss is required.

  3. The 800 calories can consist of real food or shakes to replace some meals.

  4. Shakes are low in sugar, high in fibre and contain essential protein, fats, vitamins and minerals. Because they are low in carbs and calories they will induce mild ketosis, which will reduce hunger and help preserve muscle.

  5. As a body switches from burning sugar to burning fat, headaches or light-headedness can ensue. These symptoms are likely to be due to dehydration which is why it is so important to drink extra water. The normal advice is 8 cups a day, or about 2 litres.

  6. As well as cutting down to 800 calories a day, a Time Restricted Eating (TRE) programme is also followed. This means, from the start, aiming for a 12-hour overnight fast.

Stage 2: The New 5:2: Sustainable Intermittent Fasting

  1. 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.

  2. This can be much more sustainable and enjoyable than constant calorie restriction, as much of the evidence points at daily calorie counting failing to be sustainable in the long run.

  3. On the days when you are not fasting, counting calories is not necessary, though it is important to be careful about portion control and maintain a healthy Mediterranean-style diet.

  4. This stage involves 5 days without calorie counting, eating a balanced Mediterranean style diet and then 2 days counting calories.

  5. At this stage the overnight fast is increased to 14 hours. The reason for doing this is that it will help maintain and enhance the benefits of intermittent fasting, in particular autophagy and ketosis.

Stage 3: Maintenance: A Way of Life

  1. Once goals have been achieved, the programme moves onto the Maintenance Phase.

  2. The longer the maintenance programme is followed, the easier and more natural it becomes.

  3. This phase is flexible enough to deal with an individual healthy living plan.

The Science Behind Intermittent Fasting and the Fast 800 Diet

Type 2 diabetes was generally regarded as an irreversible chronic condition. However, research has shown that a very low-calorie diet can bring about acute return to normal glucose control in some people with Type 2 diabetes and for these people to remain free of diabetes. Gradual accumulation of fat in the liver and pancreas leads eventually to beta cell dedifferentiation and loss of specialised function. Evidence now shows that people with Type 2 diabetes who successfully lose weight can reverse their condition because excess fat is removed from their liver and pancreas, returning insulin production to normal.

The original study conducted by Professor Roy Taylor, has shown that in just eight weeks’ participants lost on average 14 kilograms and over the following 6 months they did not regain any weight. Many of the participants had suffered with Type 2 diabetes for more than eight years and ranging up to 23 years. Overall, 12 out of 30 participants who had had diabetes for less than 10 years reversed their condition. Six months later they remained diabetes free. Though the participants lost weight they remained overweight or obese but they had lost enough weight to remove the fat out of the pancreas and allow normal insulin production. The study suggests that every person has their own personal fat threshold, which determines how much fat they can put on before they develop problems such as the accumulation of fat around the liver and pancreas, which can then lead on to insulin resistance and then Type 2 diabetes. The study further suggests that if the individual person loses that amount of weight then their body returns to normal.

Professor Roy Taylor, Professor of Medicine and Metabolism at Newcastle University, who also works within Newcastle Hospitals is a world-renowned academic scientist; and it is his research that The Fast 800 diet is based on.

Combating Type 2 Diabetes and Obesity

In the UK, about two-thirds of the adult population and one-third of children are currently overweight or obese, with more than 15 million obese people in the UK. Type 2 diabetes is strongly linked to being overweight or obese and affects 7,000 under 25s in England and Wales. Type 2 diabetes is a condition that causes glucose levels in the blood to become too high. The hormone insulin, produced by the pancreas, is responsible for controlling the amount of glucose in the blood, however, in Type 2 diabetes the pancreas doesn’t produce enough insulin or the body’s cells don’t react to insulin produced.

Diabetes can cause serious long-term health problems and is the most common cause of vision loss and blindness in people of working age. Diabetes is also responsible for most cases of kidney failure and lower limb amputation, other than accidents and people with diabetes are up to five times more likely to have cardiovascular disease, such as a stroke. Thus, it is vitally important to combat Type 2 diabetes and the burden the disease places on the NHS, where currently 10% of its budget is spent on treating diabetes.

The Fast 800 Diet and NHS England

Thousands of people with Type 2 diabetes in England are to be prescribed the Fast 800 diet with the aim of reversing their condition. When the diet was trialled last year, almost half of those involved managed to put their diabetes into remission. The NHS England is initially prescribing the programme to 5,000 patients on the cusp of developing Type 2 diabetes, with the aim of preventing the onset of the disease. The implications for personal health and for the NHS are considerable.


The Fast 800 Programme – The Science of Healthy Living: https://thefast800.com/

Mosley M (2019) The Fast 800: How to combine rapid weight loss and intermittent fasting for long-term health. Short Books Ltd.

Taylor R (2019) Calorie restriction for long-term remission of type 2 diabetes. Clin Med (Lond) 19(1):37-42.

Steven S et al. (2016) Very Low-Calorie Diet and 6 Months of Weight Stability in Type 2 Diabetes: Pathophysiological Changes in Responders and Nonresponses 39(5):808-15.