What is the Fast 800 diet? (2023)

What is the Fast 800 diet?

Developed by Dr Michael Mosley of BBC Two’s Trust Me, I’m a Doctor, the Fast 800 diet claims to potentially cut your risk of type 2 diabetes, heart disease and cancer and, because stage one is a very low-calorie diet (VLCD), possibly reverse type 2 diabetes. The diet is aimed at those wishing to lose weight, especially if they carry excess abdominal fat, as well as those with blood sugar issues, including pre-diabetes and type 2 diabetes. Michael designed the diet based on the research performed by Professor Roy Taylor of Newcastle University including the DiRECT study, funded by Diabetes UK.

What does the Fast 800 diet involve?

The Fast 800 diet brings together the concepts of Michael Mosley’s previous books, including the 5:2 diet and the Blood Sugar Diet, and combines them with knowledge gained from recent research relating to intermittent fasting and low carb or low calorie diets.

Fast 800 starts with a rapid weight loss phase. You are advised to stay in stage 1 for a minimum of 2 weeks and no more than 12 weeks, and during this time you follow a daily 800-calorie eating plan. You do this by following a relatively low-carb Mediterranean-style diet, with lean protein sources and vegetables. On days when cooking is not possible, meal replacement shakes are available – these are high in protein, fibre and healthy fats. The plan recommends no more than two shakes per day or more than 10 per week, with the emphasis instead placed on whole, natural foods. Those adopting this stage of the plan typically have either a lot of weight to lose, require fast results, have reached a weight loss plateau or have type 2 diabetes. Stage 1 is designed to switch the body from burning sugar to fat burning by prompting mild ketosis.

The second stage of the plan involves intermittent fasting, restricting calories to 800 a day for two days of the week, then eating a healthy, low-carb Mediterranean diet for the remaining five days. This stage offers an opportunity to embrace home cooking, reduce processed foods and focus on vegetables, wholegrains, nuts, seeds, legumes, healthy fats and lean protein. The plan recognises that sustaining protein intake is important to maintain muscle mass and support metabolism. The plan also suggests time-restricted eating to enhance the benefits of fasting.

Once you’ve achieved your goal weight, you enter the maintenance phase. This phase is designed to fit personal goals and to work with your lifestyle; you’ll continue with the Mediterranean style of eating, following a low sugar diet with limited amounts of starchy carbs, with a weekly fast day, if needed.

(Video) Revolutionary Fast 800 Diet | A Current Affair Australia

Is the Fast 800 diet healthy?

Whether the Fast 800 will be beneficial for you will depend on your circumstances. One of the goals of the Fast 800 is to target metabolically active abdominal fat – this fat puts people at risk of lifestyle diseases, like type 2 diabetes. The first stage of the diet works on the premise that when we eat refined, typically ‘white’ carbohydrates, like white bread, pasta and rice, they are easily broken down in the gut to release sugars which over time leads to fat accumulation and possible insulin resistance. The aim of this stage of the diet is to normalise liver and pancreas fat and promote regular insulin response and blood glucose management.

However, adopters should be aware that this rapid weight loss stage can be intense and may have a significant impact on blood sugar levels, so if you are prescribed diabetic medication or insulin you must discuss the plan with your GP and secure their ongoing support and monitoring for the duration of the plan.

During first stage you may also experience side effects – the most common are headaches, constipation or tiredness. This is typically due to dehydration, so the plan encourages you to increase your intake of calorie free liquids to 2-3 litres per day.

(Video) 'The Fast 800' Author Dr Michael Mosley Answers Our Dieting Questions | Studio 10

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If you choose not to use a meal replacement product during this stage, micronutrient intake may be low and a vitamin and mineral supplement may be needed to support nutrient intake. Meal replacement products, such as shakes, are designed to help stave off hunger so if you do elect to follow the ‘real food’ version of the plan you may also be challenged with hunger pains.

Is the Fast 800 diet effective for weight loss?

VLCD, those supplying 800 calories or less, can lead to rapid weight loss, but may not be suitable or safe for everyone and they are not routinely recommended by the NHS. Typically, they are only recommended if you have an obesity-related complication which would benefit from rapid weight loss. The NHS advise that for the majority of us to lose weight in a safe and sustainable way, we should reduce our calorie intake to 1,900 calories for men and 1,400 calories for women.

Dr Mosley claims that by following the rapid weight loss stage of the Fast 800 you may lose as much as 14kg over 8 weeks. This does depend on your start weight, how much you need to lose and assumes you remain motivated and committed throughout this challenging phase. Stage two of the plan offers a more sustainable period from which to progress weight loss at a slower rate.

What is the Fast 800 diet? (2)

Is the Fast 800 diet safe to follow in the long term?

The NHS suggest that should you choose to follow a VLCD you should do so for no longer than 12 weeks and under the guidance of a suitably qualified healthcare professional. Dr Mosley also cites 12 weeks as the maximum period for the rapid weight loss stage of the Fast 800 and that, thereafter, a low-carb Mediterranean diet is followed.

(Video) 14 days on the Fast 800 diet - what to expect.

Restricting calories over a long period of time will limit your intake of nutrients and energy, especially if you follow the ‘real food’ version of the plan. Meal replacement shakes are typically fortified with vitamins and minerals and supply protein and essential fats which may help fulfil your nutrient requirements, however, they are still a tool for short-term use only.

Although there are no reported Fast 800 trials the DiRECT study led by Professor Roy Taylor, which inspired components of the Fast 800 diet, continues to monitor participants. The study reported their second year findings which suggest that intensive weight management has the potential to reduce or delay the complications of type 2 diabetes.

Who shouldn’t follow the Fast 800 diet?

It is advisable to refer to your GP or healthcare professional before starting a new dietary regime especially if you are under 18 years old, elderly, have a pre-existing medical condition, including type 2 diabetes or are on medication. You may need your GP’s support to make changes to your medication and to monitor your blood sugar or blood pressure levels as you progress through the plan. You should also consult your GP if you’re taking warfarin, are on blood pressure tablets, are pregnant, breastfeeding or undergoing fertility treatment.

In addition, The Fast 800 Diet is not recommended for people who are underweight or have an eating disorder, are type 1 diabetics, have had a heart condition or are recovering from surgery. The 800 calories restriction is also not appropriate for anyone participating in endurance exercise.

Please note: if you're considering attempting any form of diet, please consult your GP first to ensure you can do so without risk to health.

Kerry Torrens BSc. (Hons) PgCert MBANT is a Registered Nutritionist with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.

(Video) Dr Michael Mosley talks to BBC Breakfast about his latest book The Fast 800


All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other healthcare professional. If you have any concerns about your general health, you should contact your local healthcare provider. See our website terms and conditions for more information.


What are the basics of The Fast 800 diet? ›

Dr Michael Mosley's latest diet encourages people to eat 800 calories per day, fast intermittently and replace some meals with nutritious shakes, in a new iteration of his famous 5:2 diet. Dr Michael Mosley has unveiled a new diet that he describes as his “best plan ever”.

How much weight will I lose on fast 800? ›

The NHS advise that for the majority of us to lose weight in a safe and sustainable way, we should reduce our calorie intake to 1,900 calories for men and 1,400 calories for women. Dr Mosley claims that by following the rapid weight loss stage of the Fast 800 you may lose as much as 14kg over 8 weeks.

What meal can I have for 800 calories? ›

  • Chicken zoodle stir-fry.
  • Blueberry and almond chia pudding.
  • Jalapeno omelette.
  • Vegetable and tofu nasi goreng.
  • Vegetable tray bake with poached egg.
  • Basil chilli turkey with sweet potato noodles.
  • Healthy vegetarian nachos.
  • Eggplant steaks with pistachio and mint quinoa salad.

Does The Fast 800 really work? ›

There is limited research to support the Fast 800 diet as being superior to other equivalent energy-restricted diets. While the evidence suggests that an intermittent fasting diet may be an effective way to lose weight, it is unlikely to be more effective for weight loss than traditional methods of dieting.

Can you eat eggs on The Fast 800 diet? ›

Start the day with eggs

Boiled, poached, scrambled or as an omelette – they'll keep you feeling fuller for longer compared to cereal or toast. Delicious with greens and parmesan or smoked salmon and a sprinkle of chilli.

Are bananas OK on fast 800? ›

Doctor Michael Mosley - the nutritionist behind a range of diets including The Fast 800 and 5:2 - advised that you should cut out some foods, including a common fruit, if you want to shed some pounds. The experts says that eating bananas is not as beneficial as you may think, reports The Express.

What does Michael Mosley eat for breakfast? ›

Writing on his website, Mosley revealed that eating eggs in the morning can be a great building block for losing weight and that a mushroom omelette is one of his own "go-to breakfasts". He wrote: "Boiled, poached, scrambled or as an omelette - they'll keep you feeling fuller for longer compared to cereal or toast."

What are the side effects of The Fast 800 diet? ›

Possible Side Effects When You First Start The Fast 800
  • Headaches.
  • Fatigue.
  • Dry mouth.
  • Feeling lightheaded.
  • A decrease in blood pressure.
  • Feeling cold.
Jun 17, 2020

What is the difference between keto and fast 800? ›

Keto, or ketogenic diets, are high-fat, adequate-protein, low-carbohydrate diets that force the body to burn fats rather than carbohydrates. The Fast 800 combines a traditional keto diet with low-calorie intermittent fasting - only 800 calories are consumed every day.

How many pounds will I lose if I only eat 800 calories a day? ›

Some people go on a very low-calorie diet for rapid weight loss, often consuming only 800 calories a day. This type of diet usually includes special foods such as shakes, bars, or soups to replace meals and for added vitamins. Very low-calorie diets can help a person achieve weight loss of up to 3 to 5 pounds per week.

What vegetables can you eat on The Fast 800 diet? ›

Think broccoli, brussel sprouts, kale, cabbage, spinach, bok choy (or pak choy) – most of the cruciferous vegetable family.
You could:
  • Add a handful of spinach in your smoothie;
  • Roast or steam and serve with your favourite protein; or.
  • Add an extra handful or two to a salad.
Mar 20, 2020

How to lose 20 pounds in a month? ›

How to Lose 20 Pounds as Fast as Possible
  1. Count calories. ...
  2. Drink more water. ...
  3. Increase your protein intake. ...
  4. Reduce your refined carb consumption. ...
  5. Start lifting weights. ...
  6. Eat more fiber. ...
  7. Follow a sleep schedule. ...
  8. Set reasonable goals and stay accountable.
Aug 13, 2018

Can I drink coffee on Fast 800? ›

Strictly speaking, black tea or coffee, herbal teas and water are the most suitable options that will not break your fast. Just steer clear of lattes if you're practising TRE and as always on fasting days, include milky drinks in your calorie intake. We always recommend full fat milk.

How much weight can I lose on Fast 800 in a month? ›

This is considered a rapid weight loss approach, and it isn't as scary as you might initially think. While The Very Fast 800 can be followed for up to 12 weeks or until you reach a healthy BMI (whichever comes first), in just three short weeks, the average weight loss across the group was 7kg, just over a stone.

Can you eat carbs on Fast 800? ›

What foods to eat on The Fast 800 Keto Diet. If you've read Dr Mosley's latest book, The Fast 800 Keto, you'll know that he recommends following the rule of 50:50. Keeping carbohydrates under 50g per day and ensuring protein remains above 50g.

Can you eat cheese on fast 800 diet? ›

Full-fat dairy products.

Such as full-fat live Greek yoghurt, cheese and butter. Healthy natural fats will keep you full for longer. When I need a snack it is a small chunk of cheese with some slices of pear.

Can you eat potatoes on fast 800? ›

The trick is not to cut carbs completely, but rather to be choosy about the ones you regularly eat. If you want to try going lower-carb then white bread, white pasta, potatoes and sugars, including maple syrup and agave nectar, are best eaten sparingly, if at all.

How much weight can you lose in 12 weeks on fast 800? ›

Dr Michael Mosley on the benefits of exercise

Determined and interested in achieving permanent weight loss and, more importantly, a healthy body, Sue turned to The Fast 800 programme, created by Dr Michael Mosely and lost nearly three stone in 12 weeks.

What you Cannot eat during fasting? ›

Strictly speaking, any amount of calories will break a fast. If a person follows a strict fasting schedule, they should avoid any food or drinks containing calories. Those following a modified fasting diet can often eat up to 25% of their daily calorie needs while fasting.

What bread is best for Fast 800? ›

Choose multi-grain, seeded or rye bread over white. Again, the good bacteria in your gut will thrive on the fibre in these foods. But during both the rapid weight loss and 5:2 stages of the diet you should keep your intake of wholegrains down.

Is bread allowed on Fast 800? ›

Sugar should be reduced or avoided, starchy carbs, like white bread and white pasta, are gone, and 45-60g of good-quality protein should be consumed daily.

What does Oprah eat for breakfast every morning? ›

Breakfast. Nearly every day begins with eggs of some sort, often one yolk and two whites. Or it might be "The Usual" Egg Sandwich, which Oprah has shared with WW. This four-point meal includes a slice of toasted wheat bread, ⅛ of an avocado, 1 over-easy egg and a medium tomato.

What does JLO eat in the morning? ›

According to People, J. Lo starts her day with protein shakes that are made up of strawberries, blueberries, Greek yogurt, cinnamon, honey, lemon juice and her Body Lab protein powder.

How much water should you drink on The Fast 800 diet? ›

85 fl.

Especially when doing intermittent fasting, a well hydrated body (meaning drinking more than the minimum amount!) is an important key to success! That is why you should pay attention to drink at least 85 fl. oz (2.5 liters) a day.

Why am I not losing weight on fast800? ›

There is no single cause of the weight loss plateau. One reason may be that when calories are significantly reduced, the body switches from using glucose to using its stores of glycogen (before then moving into fat-burning mode) in the muscles and liver.

How long can you stay on a 800 calorie diet? ›

The 800-calorie rapid weight loss phase is safe for most individuals for up to 12 weeks, as long as you stick to our recommendations, drink plenty of water and use a multivitamin.

Can you eat fruit on the keto 800 diet? ›

How to follow The Fast 800 Keto Diet. Following a keto diet basically means reducing the amount of carbohydrates you eat, while increasing protein, healthy fats, fruit and vegetables. This dovetails perfectly with the life-extending Mediterranean diet, built around fruit, vegetables, seafood, beans and nuts.

How much protein should I eat on fast 800? ›

On The Fast 800 Keto, the calories are 800-1000/day. Within this, you consume at least 50-60g of protein, around 20g or less carbohydrates (so you can still add extra low-calorie non-starchy veg without having to worry about counting extra carbs) and the remainder is made up with healthy fats.

Can you drink milk on The Fast 800 diet? ›

So, generally, anything with calories in it will break your fast. Although, Dr Mosley has said that a splash of milk (1 to 2 teaspoons) should be okay. If a dash of milk in your morning tea or coffee is helping you sustain a healthy way of eating, then it's likely not detrimental to your efforts.

Which snack is lowest in calories? ›

25 Super Snacks With 100 Calories or Less
  • 1/2 Cup Slow-Churned Ice Cream. 1/25. Surprise! ...
  • 6 Cups Microwave Popcorn. 2/25. ...
  • Cottage Cheese and Cantaloupe. 3/25. ...
  • Three Crackers With Cheese. 4/25. ...
  • Fourteen Almonds. 5/25. ...
  • Six Whole-Grain Pretzel Sticks. 6/25. ...
  • Baked Apple. 7/25. ...
  • Cheese-Stuffed Pita Pocket. 8/25.
Feb 22, 2022

What did Kim K eat to lose 16 pounds? ›

According to Healthy Balance, Kim Kardashian's 3-week weight loss journey involved her cutting carbs and eating “just the cleanest veggies and protein.” When it came to working out, Kim ran on a treadmill and wore a sauna suit twice a day.

Can I eat around 800 calories a day? ›

A very low calorie diet is a clinically supervised diet plan that involves eating about 800 calories a day or fewer. They are sometimes considered for obese and severely obese people who are managing diabetes, going to have surgery or preparing for fertility treatment.

What fruit to avoid on fast 800? ›

The Fast-800 website also states that slimmers should avoid eating melons and pineapples too often, as they also contain high levels of sugar.

Can you have cucumber on fast 800? ›

We encourage you to eat non-starchy vegetables alongside your meals. The vegetables shown contain more calories than the vegetables you can eat liberally, such as broccoli and cucumber, therefore count calories when including them on fasting days.

Can I have butter on fast 800? ›

As a concentrated dairy product, we're not advising you to lather butter onto every meal; however, a small amount every now and then will cause far less harm than processed margarine and spreads.

What is the strongest weight loss pill available? ›

PhenQ is our top pick for the best weight loss pills in 2023. It's a comprehensive formula that utilizes specialized ingredients to achieve results. This supplement is designed to help burn fat, suppress your appetite, and boost your energy levels while preventing new fat cells from forming.

What is the 4 4 12 rule? ›

Unicity recommends a form of intermittent fasting we refer to as 4-4-12. 🕓 By waiting 4 to 6 hours between breakfast and lunch, and lunch and dinner, and waiting 12-16 hours between dinner and breakfast with no snacking in-between, we give our bodies the time needed to get into what we call the FAT BURNING ZONE.

Can you drink Coke Zero on Fast 800? ›

Because diet soda doesn't have calories, it's usually OK to drink while you're fasting.

Are The Fast 800 shakes keto friendly? ›

A convenient, low-calorie Protein Booster, especially helpful on fasting days. This simple plant-based formula is low in salt, with no added sugar, artificial additives or preservatives. Can be used as a standalone protein shake or in a wide variety of recipes, and is keto-friendly and suitable for vegans.

Can I lose 20 pounds in a month by fasting? ›

5:2 Intermittent Fasting. Weight loss studies surrounding intermittent fasting have typically investigated the 5:2 diet or alternate-day fasting interventions lasting three to six months. The research revealed that it takes four to six months to lose 20 pounds with no change in diet.

Can you lose weight eating 800 calories 2 days a week? ›

This makes the fast days a little easier (!) and consuming up to 800 calories is still effective for weight loss. The advantage of the 5 2 diet is that you only need to eat less on 2 days a week, which can make the diet easier to follow in the longer term than struggling to eat less every day.

How quickly do you lose weight on The Fast 800? ›

The NHS advise that for the majority of us to lose weight in a safe and sustainable way, we should reduce our calorie intake to 1,900 calories for men and 1,400 calories for women. Dr Mosley claims that by following the rapid weight loss stage of the Fast 800 you may lose as much as 14kg over 8 weeks.


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