I went on the fast 800 diet to lose weight and get healthy in time for upcoming surgery. I tracked everything on a daily basis, for accountability and so I can help to motivate fellow fast 800’ers who are just starting out.
I’ve learned what works and what doesn’t, so in each weekly update, I’ll be giving tips and tricks which might help you as you progress through your journey.
In this post, I’ll be taking you through my experience of week one on the fast 800 diet, along with weight and measurement facts and figures.
Important Info
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. (For more information check the Fast 800 Medical Disclaimer Page).
Just to let you know some of the products on this page have Amazon Associates affiliate links. I only recommend products which I feel might be helpful for a particular topic. I may receive a small commission for the recommendation however, I only link to quality products and in most cases those, I have tried – for more information please see my privacy policy.
Fast 800 Week One Weight Loss
I weighed and measured myself on day one and then again at the end of week one and found that by sticking to the fast 800 plan for one week I lost 6lb in weight and my waist measurement dropped by 5cm.
Below are all of the figures and conversions into both metric and imperial:
| Measurement | Starting figures | Figures at the end of week one |
| Weight | 13st 10lb/ 192lb/87kg | 13st 4lb/186lb/84.3kg |
| Weight loss so far | N/A | 6lb/2.7kg |
| Waist measurement | 107cm/42in | 102cm/40in |
| Waist reduction | N/A | 5cm/2in |
| BMI | 30.1 (obese) | 29.2 (overweight) |
| Milestones met | N/A | Went from an ‘obese’ BMI to ‘overweight’ |
| Fast 800 method used | N/A | The Very Fast 800 (800 calories per day) |
| Time-restricted eating (TRE) | N/A | 16-18 hours (6-8 hour eating window) |
| Carb/protein/fat macros | N/A | Around 30g carbs/60g protein/49g Fat |
After the hard work I put into the first week I was very happy with my progress, especially because I’m fairly inactive due to arthritis pain.
I realize that week one was always going to be a big one (losses-wise) and that most of this will be water loss.
Everyone’s experiences vary so some people lose more and some people lose less, so the key is to keep going and to stay motivated because you will lose weight if you stick to the plan.
It’s also worth noting that I have been practicing TRE for a while so it’s quite easy for me to only eat in a small window each day.
Starting out at 12 hours is much easier if you’ve not done TRE before and still helps to boost the effects of the diet.
Future Planning
I plan to stay on ‘the very fast 800’ version of the plan until the maximum period of 12 weeks is up so I can report my findings here, but how you do it is up to you.
The author of the book (Michael Mosley) recommends that you stay on the very fast 800 plan for at least two weeks and up to a maximum of 12.
After then, if you still have weight to lose, it’s recommended that you move on to a 5:2 plan where you eat 800 calories for two days a week and sensibly for the remaining five days.
If you don’t need to lose any more weight then you can maintain a healthy diet by sticking to a Mediterranean-style diet with a few more treats than you could have on the very fast plan.
Tracking Your Food & Progress on the Fast 800 Diet
For me, the key to staying motivated and making sure I don’t go off track is by keeping a note of my progress, tracking everything I eat, and daily weighing.
This way if anything starts going wrong, then I can quickly get back on track before things escalate.
Tracking progress
Tracking your progress on a daily or weekly basis is really useful so that you can see what’s worked and what hasn’t.
How you do this is up to you, I use a spreadsheet, but you can write it in a journal, on an app, whichever is easiest.
Keep a track of your weight and measurements so you can look back and see how far you’ve come because this is the best motivation of all.
Tracking Food and Drink
Tracking food and drink is one of the most important things you can do from day one because it’s the only way you can know for sure that you’re not exceeding 800 calories.
It’s also important to make sure you’re consuming enough calories too.
There are lots of trackers out there, some are better than others, and the more comprehensive the better.
I like MyFitnessPal because pretty much every food you ever need to track is on there and you can check your nutrient intake too. The free version is enough to get everything you need.
Daily Weighing
Daily, or if not, weekly weighing is helpful because it helps you to know straight away if you’ve started to go off track.
The only downside to daily weighing is that it can sometimes be demotivating when you don’t lose for a few days or you gain a pound or two when you’ve been trying really hard.
Ultimately, the advantages of daily or weekly weighing, pay off and help to keep you motivated when you’re losing weight.
How Long Does the Fast 800 Take to Work?
When you start the very fast 800 version of the diet, it’s only natural that you want to see results on the scale after day one.
This is because going from a high-calorie diet to a very limited one can seem like a big deal in the early days.
I didn’t notice any change in weight until around two-three days into the diet while my body adjusted, and then once ketosis kicked in, my weight started to quickly drop during the rest of week one.
This initial lack of scale movement can be demotivating when you’re working so hard, if you have the same thing, don’t worry it will happen!
Going into Ketosis on Week 1
As part of the fast 800 plan, the idea of the diet is to eat low carb foods especially in the early days when you’re following the very fast 800 version of the plan.
Keeping carbs under a maximum daily amount of 40-50g will cause your body to go into a mild to moderate state of ketosis which means your body switches from burning glucose to fat.
If you incorporate TRE into your plan, this helps to boost the fat-burning effect along with the low-carb diet.
It takes around 2-4 days to go into ketosis and during this time it’s normal to feel generally unwell and tired.
This is known as the ‘keto flu’ and it will usually pass after the first week, but it can be enough to put people off continuing with the diet.
Having been through this stage myself, my best advice would be just to push through it, because you will feel a million times better in the days/weeks to come.
By going into ketosis, you’re turning your body into a fat-burning machine, which is the thing that’s going to keep your weight loss going over time.
You can check if you have gone into ketosis, you can get simple and inexpensive keto sticks that you can dip into your pee.
These sticks are a useful guide to show if you’re eating the right amount of carbs, or if you need to make some adjustments to reduce your daily intake.
I recommend and use the keto sticks available in the following Amazon link:
Ascensia Ketostix Reagent Strips (Ketone)
What I Ate to Lose Weight in Week 1
The fast 800 book and the recipe books contain lots of recipes and these are really good to make sure you’re getting the right amount of nutrients.
Some people follow this to the letter, but some choose to follow their own plan based on the principles of the diet.
I like to cook, so I do a mixture of both my own recipes and those from the books. If you like to know the detail, then here’s what I had on week one:
| Day | Food eaten | Calories Kcal |
| Monday brunch | Smoked salmon, scrambled eggs & tomato | 330 |
| Monday dinner | Prawn & veggie stir fry with cauliflower rice | 392 |
| Tuesday brunch | Smoked salmon, scrambled eggs, cheese & tomato | 384 |
| Tuesday dinner | Swede topped cottage pie (from the book) & veg | 377 |
| Wednesday breakfast | Greek yogurt, stewed plums & chopped cashews | 198 |
| Wednesday lunch | Cheese omelet with salad | 176 |
| Wednesday dinner | Cheeseburger (no bread), celeriac chips & salad | 453 |
| Thursday brunch | Greek yogurt, stewed plums, chopped cashews & milled flaxseed | 294 |
| Thursday dinner | Steak, celeriac & halloumi chips & veg | 503 |
| Friday breakfast | Greek yogurt, stewed plums & milled flaxseed | 224 |
| Friday lunch | Cheese omelet with salad | 205 |
| Friday dinner | Swede topped cottage pie (from the book) & veg | 377 |
| Saturday breakfast | Greek yogurt, blackberries & milled flaxseed | 223 |
| Saturday lunch | Bacon, eggs & tomatoes | 338 |
| Saturday dinner | Barbeque – sausage, cheeseburger & salad (no bread) | 604 |
| Sunday breakfast | Greek yogurt, blackberries & milled flaxseed | 237 |
| Sunday lunch | Fried halloumi & salad | 212 |
| Sunday dinner | Roast pork, yorkshire puddings & veg | 402 |
I stuck to slightly under or over 800 calories per day, with a slightly naughtier day on Saturday when we had some friends over.
Just a note on the Yorkshire puddings on Sunday, these are pretty high in carbs and a small, but I kept the rest of the day really low in carbs and stayed in ketosis the following day.
I include lots of green vegetables with each meal, these are usually a combination of:
- Broccoli
- Cabbage
- Green beans
- Sprouts
- Spinich
How Many Meals Should You Eat on Fast 800?
One of the big questions, when you start the fast 800 diet, is should you have two larger meals or three smaller ones.
This is something that you really need to test to find out what works best for you as you can see in my week one (above) I did a mix to see what worked best.
If you’re using TRE and not eating until mid-morning or even lunchtime, then only having two meals is very easy.
The benefit of having two meals is you can have larger meals so you’re more likely to fill up and there’s less food to prepare.
It takes a bit of getting used to but once you get into the routine it’s pretty easy and pain-free to have two meals per day and some people even have just one.
Eating enough fiber
One of the things I noticed in the first few days of the fast 800 diet, was that I wasn’t eating enough fiber, so I researched low carb high fiber foods and incorporated the following into my diet:
- Flax seed – I use milled high fiber seed sprinkled over yogurt
- Broccoli
- Berries – blackberries & raspberries
- Pistachios
- Cauliflower
You can get milled flax seed from Amazon via the link below, this was a game-changer for me and it helps to make you feel fuller:
Linwoods Organic Milled Flaxseed, 425 g – Pack of 2.
Tips for Getting Through Week 1 on the Fast 800 Diet
Here are some of the main things that I learned in the first week of the fast 800 diet, which you might find helpful:
- Don’t worry if you don’t see any losses on the scale in the first few days.
- Make sure you have between 45-60 grams of protein per day to make you feel fuller and to maintain muscle health.
- Track how many carbs you’re eating to make sure your in ketosis.
- Eat plenty of low carb vegetables because they make you feel fuller for longer.
- If you’re not feeling great, don’t worry you will feel better in the coming days once your body gets used to things.
Key Takeaways
- Week One Results: After adhering to the Fast 800 diet for one week, I experienced a weight loss of 6lb and a waist measurement reduction of 5cm.
- Ketosis and the ‘Keto Flu’: The Fast 800 diet aims to induce a state of ketosis by limiting daily carb intake to 40-50g. Transitioning into ketosis can lead to symptoms known as the ‘keto flu,’ which includes feelings of fatigue and general unwellness, but these symptoms typically subside after the first week.
- Time-Restricted Eating (TRE): Incorporating TRE, where one eats within a 6-8 hour window and fasts for the remaining hours, can enhance the fat-burning effects of the diet.
- Dietary Choices: The author shared a detailed meal plan for the week, emphasizing the importance of including green vegetables and ensuring adequate fiber intake. Foods like milled flaxseed, broccoli, berries, and cauliflower were highlighted for their high fiber content.
- Tips for Success: Some advice for those starting the Fast 800 diet includes being patient with initial weight loss, ensuring adequate protein intake, tracking carb consumption to maintain ketosis, and consuming plenty of low-carb vegetables for satiety.
Related Articles
For more information on what the fast 800 diet is and how to do it, take a look at my ultimate guide in the link below:
The Fast 800 Diet – Review & Week By Week Weight Loss Updates
To see what you can expect in week two, click the link below: