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The Fast 800 Diet – Review & Week By Week Weight Loss Updates

In this ultimate guide and review of the fast 800 diet, I’m going to take you through my own experiences, the type of foods you can eat on the diet, along with lots of facts and statistics taken from my own measurements week-by-week.

I am self admittedly a serial dieter, who has tried pretty much every diet out there and I usually fail within the first week, so I’ve made it my mission to stick to a weight loss target and to find a diet that actually works – starting with the fast 800 diet.

I’m also a massive geek, so I thrive on charts, figures, graphs, and knowing every little detail inside out – sad I know.

So, I thought I’d put this geekiness to some use by sharing this information, so if like me you get motivated by numbers and success stories, this guide and my week-by-week results might help to motivate you to achieve your own personal goals.

Before I begin, it’s important to know that the information on this page is purely my own experience and I am not a health professional. This diet is not suitable for everyone, especially if you have an existing health condition or history of an eating disorder (see below for more information).

What is the Fast 800 Diet?

The Fast 800 diet is a program which has been developed by UK doctor Michael Mosley, who famously developed the 5:2 fasting diet (where you eat 500-600kcal for two days a week and eat normally but sensibly for the other 5 days).

The Fast 800 program has been developed to make fasting days easier with an increased allowance of 800 calories per day on a fast day.

The diet generally consists of three main elements, which include:

  • ‘The very fast 800’ where you only eat 800 calories per day for around two weeks or up to a maximum of 12 weeks. This helps to kick start your diet with rapid weight loss to motivate you to continue with your journey.
  • ‘The new 5:2’ – intermittent fasting by eating 800 calories for two days and a healthy mederteranian diet with more calories on a non-fast day.
  • Maintenance – an ongoing way of eating to help you to maintain your weight and a healthy lifestyle once you’ve reached your goals.

Time-restricted eating TRE is also encouraged as an addition to the fast 800 program because it helps to maximize the benefits.

You can also sign up for the full 12-week program paid subscription which offers full step-by-step guided weight loss including recipes, exercise programs, meal plans and much more – for more information visit the Fast 800 site here.

How you chose to do this is up to you depending on what you’re looking to achieve and what you feel comfortable with.

The food you eat is generally low in carbs, (although not as strict as the keto diet) and is based on a Mediterranean way of eating with lots of fresh healthy foods (see below for more information).

Why I Chose to Try this Diet

I don’t want to bang on about me, but here’s a little bit of information on why I chose to start with fast 800 over the other many diets which are out there, (and to be clear, I don’t receive any kind of commission from Fast 800 for promoting the diet).

I started on Fast 800 because I had to lose weight for my health and because was on a waiting list for a double hip replacement (at 42).

I was classified as obese at 13 stone 10 pounds/ 192lb/87kg, my BMI was just over 30 and my waist was measuring 42 inches (107cm).

I was feeling sick, exhausted, and sluggish and I knew that if I stayed this way I’d only pile on more pounds, leading to further health problems, and would be at higher risk of complications during surgery.

I’ve always battled with my weight, but because of lockdown and the fact I was becoming less mobile, things were getting worse by the week.

So I had a do-or-die moment, where I knew that I had to go all out to get the results I wanted, not only to lose weight but to improve my health too.

Having tried the Fast 800 in the past (but not for long), I knew it would give me the quick results I needed before my hip surgery. The fast 800 diet is proven to show quick results, which helps to motivate people to carry on in the early days.

My main weight loss target is 10 stone, which means I plan to lose as close to 3 stone 10lb (52lb/23kg) which would take me into the mid-range of a healthy BMI.

I plan to do this relatively quickly, through rapid weight loss in the first few weeks, followed (hopefully) by a steady 2lb loss per week after the first month.

My Story on Fast 800 – Week by Week

This part of the page is a work in progress because my journey is still ongoing, so I’ll update this section and post a comprehensive results page for each week as they go by.

I will also be uploading before and after pictures, but because I’m not at the ‘after’ stage yet, they’re not ready just yet.

Week 1

WeekWeightWeight loss so far
Start13 stone 10lb (192lb/87kg)N/A
113 stone 4lb (186lb/84.3kg)6lb/2.7kg
213 stone 0lb (182lb/82.6kg)10lb/4.5kg

For lots more in-depth information week-by-week, click on the links below to see the individual articles:

Fast 800 Results – Week 1 (With Tips and Food Ideas)

Fast 800 Results – Week 2 (Complete Update)

Who Shouldn’t Do the Fast 800 Diet?

Although there are many health benefits associated with the fast 800 diet, this style of dieting is not appropriate for everyone.

If you have any pre-existing medical conditions, you’re pregnant, breastfeeding, under 18, or have any previous history of an eating disorder, please head over to the fast 800 medical disclaimer page for more information.

The ‘very fast 800’ element of the diet is also not appropriate for those who don’t need to lose weight, however, the maintenance aspect of the plan can be very good for those who don’t need to lose weight but are looking to improve their health.

How Much Weight can you Lose on the Fast 800 Diet?

How much weight you can lose on the fast 800 plan will depend on a number of factors including your starting weight and which plan you opt for.

Many people who follow the very fast 800 plan report losing a large amount of weight in the early stages of the diet and it is not unusual for dieters to lose a stone (14lb/6.4kg) in the first three weeks if they stick to the plan.

After the first three weeks, many dieters find that their weight loss slows a little to 1 or 2lb per week rather than the high numbers seen in the first weeks.

The Fast 800 Diet and Ketosis

As well as consuming 800 calories (on fast days) it’s recommended that the food you eat should be low in carbs.

Eating a low-carb diet along with a reduced amount of calories puts your body into a state of mild ketosis, which in simple terms means it changes the fuel it burns from sugar (glucose) to fat.

It usually takes around 2-4 days to go into ketosis providing you’re eating the right foods and once you do, the fat burning and weight loss really begins!

I try to stick to a maximum of around 30g of carbs per day to stay in ketosis, although I can go up to 40-50 now and again without any impact.

How many carbs you can consume to stay in ketosis does vary from person to person, but a cheap and effective way of checking is by using keto sticks to check your urine.

I recommend and use the keto sticks available in the following Amazon link:

Ascensia Ketostix Reagent Strips (Ketone)

Time-restricted eating is also a great way to boost the ketosis effect, this can be anything over 12 hours of fasting, which is easily done if you don’t eat between 8 pm and 8 pm.

With practice, you can increase fasting time to an amount that is comfortable for you. I generally fast for 16-18 hours per day, by not eating from 6 -7 pm to around 11 am-12 pm the following day.

Nutrient Macros for the Fast 800 Diet

I looked everywhere to find the recommended macros for this diet, so I just wanted to add this in to save you some time.

It’s not essential that you stick to fixed fat/carb/protein macros, but I like to because I know that by keeping under a certain amount of carbs I can stay in ketosis.

Michael Mosley also mentions in the books, that you should try to make sure you have 45-60g of protein a day, to protect your muscles, bones, and other body functions.

So using this information for an 800 calorie fast day I’ve set my macros at:

Carbs 30g/15%

Protein 60g/30%

Fat 49g/55%

This is just a rough guide and I regularly go under or over these amounts, but it just gives a baseline to stick to the principles of the diet, which are to keep carbs low and to make sure you get enough protein.

There is wiggle room to have more carbs if you can’t cope with the lower amount, it really depends on what works for you.

Many people have reported success without tracking macros in this way, so don’t worry if it seems a bit too daunting.

What Can You Eat on the Fast 800 Diet?

Michael Mosely recommends that you stick to traditional Mediterranean-style food, in the sense that the food you eat is fresh, healthy, and fairly low in carbs.

Although the food is Mediterranean-style, this method transfers over into many types of dishes from around the world including curries, Asian food, and traditional recipes.

Processed and sugary foods are off the menu, but it is not as restrictive as the keto diet because you can eat most vegetables with the exception of very starchy veg such as potatoes.

White rice and pasta are off the menu, but you can have wholegrain alternatives on non-fast days or when you’re not following the very fast 800 version of the plan.

Good fats are allowed and recommended, as part of your daily menu, these include olive oil, coconut oil, and rapeseed.

You can also have full-fat dairy products such as greek yogurt, butter, creme fraiche, most cheeses, and cream cheese.

Unprocessed meats and fish are part of the daily routine, but there are alternatives if you’re vegetarian or vegan.

For the diet to work efficiently in the early days, while on the very fast 800 version of the plan and to stay in ketosis, you need to keep your daily total carb intake under around 50g and it’s recommended that you have up to 45-60g of protein per day.

The rest of your daily intake is made up of good fats, which might seem a little strange on a diet, but because you’re switching to burning fat when you’re in ketosis, fat is your fuel.

For an idea of the typical foods, you could expect to eat, take a look at my weekly trackers (in the links above) to find out more.

What Can You Drink on the Fast 800 Diet?

When it comes to drinks on the fast 800 diet, water will be your best friend, although other drinks are allowed.

It’s normal to be very thirsty in the early days as your body goes into a mild state of ketosis and it’s important to keep well hydrated.

Tea and coffee are allowed, and you can have them black during fasting periods without breaking a fast, although it’s suggested that you don’t have too much caffeine per day.

Although they don’t contain sugar, sugar-free fizzy drinks are not recommended on the fast 800 plan, but the occasional one is ok if you really need to.

I generally just stick to water and have a black tea in the morning before I break my fast, it gives you a boost to keep going and actually fills you up for a while, keeping hunger at bay.

You can make water more exciting by adding fruits such as lemon, lime, or berries for extra flavor.

When it comes to alcohol, the advice is that it’s best to avoid it if you can when you’re on the very fast 800 plan, although a glass of red wine is allowed on non-fast days as part of the Mediterranean diet.

Do You Need Books for the Fast 800?

It would be difficult to do the diet without reading or listening to the full fast 800 book which gives you a full background on the benefits of this type of diet along with information on the best way to do it properly.

Because 800 calories isn’t much, the recipes really help you to get the best out of the allowance by feeling as full as possible, while still getting the right amount of nutrients.

It’s very easy to just eat anything up to the value of 800kcal, however, without understanding which foods are best on the diet you can quickly use up your allowance on foods that make you feel more hungry and could leave you lacking in the right nutrients.

I would recommend the following two books which will give you all the information and recipes which you need to get you started (Amazon affiliate links):

The Fast 800 Diet Book

The Fast 800 Recipe Book

Other nice to have books (but not essential) books related to the fast 800 diet are:

The Fast 800 Easy – easy recipes to make the food element of the diet more simple

The Fast 800 Keto – (out 30th December 2021)

You can also save by getting a five-book bundle, including the diet book, recipe books, and journal so you can track your progress:

The Fast 800 five book bundle

Is Fast 800 Easy?

As with any diet, the fast 800 plan can seem a little complicated at first, but once you understand the principles, it’s easy as long as you plan your weekly foods properly so you don’t panic and eat the wrong things.

My top tips to keep things as simple as possible are:

  • Make sure you have all the ingredients you need.
  • Weigh and measure everything – if you guess, you could be having too many/little calories per day.
  • Track all of your calories on a tracker such as MyFitnessPal (the free version is fine).
  • Make food in batches so you always have spares for a busy day.
  • Try a variety of foods so you don’t get bored of eating the same things.
  • Use a good low carb/high protien meal replacement shake now and again if you’re busy.

Key Takeaways

  • About the Fast 800 Diet: Developed by UK doctor Michael Mosley, the Fast 800 diet is an evolution of the 5:2 fasting diet. It allows for 800 calories per day on fasting days, making it easier to adhere to than the traditional 5:2 diet.
  • Three Main Elements: The diet comprises three stages:
    • ‘The very fast 800’ for rapid weight loss by consuming only 800 calories daily for up to 12 weeks.
    • ‘The new 5:2’ which involves intermittent fasting with 800 calories for two days and a Mediterranean diet on non-fast days.
    • Maintenance to sustain weight and promote a healthy lifestyle after achieving goals.
  • Time-Restricted Eating: Alongside the calorie count, the diet encourages time-restricted eating (TRE) to maximize benefits, such as fasting for 12 hours or more.
  • Food Choices: The diet emphasizes a Mediterranean-style of eating, focusing on fresh, healthy, and low-carb foods. While processed and sugary foods are discouraged, good fats like olive oil and coconut oil are recommended.
  • Safety and Suitability: The Fast 800 diet may not be suitable for everyone, especially those with certain health conditions or a history of eating disorders. It’s essential to consult with a health professional before starting the diet.

Final Words

If you’re thinking of starting out on the fast 800 diet and you’re safe to do so, then my advice is, be ready, know all the facts and then go for it!

If you stick to the principles, you will lose weight and you’ll be amazed at how much you lose and just how quickly it happens.

Not only will you look better but after you get used to things you’ll feel amazing too and the health benefits are 100% worth a little pain in the beginning.

Good luck!