5:2 diet / The Fast Diet

Note: My husband joined me on this one. Neither of us are/were trying to lose weight but we are both interested in the other benefits intermittent fasting is purported to have.

What is the 5:2?

It is an Intermittent Fasting diet that was devised and popularised my TV presenter, journalist and doctor, Michael Moseley (I’m a bit of a fangirl when it comes to his work! 📺 📰 ). Check out the 2012 Horizon episode “Eat, Fast and Live Longer” on BBC iPlayer.

It involves eating normally 5 days a week and on 2 non-consecutive days, and reducing calorie intake to 25%. On average, this would be 500kcal for women and 600kcal for men (based on the general 2000kcal and 2500kcal recommended daily allowance). The reason for the calorie difference between men and women is that men tend to have more muscle mass and less fat than women and therefore burn more calories on a daily basis than women.

Although Michael Moseley recommends the Mediterranean diet, this eating protocol can be used alongside other eating plans such as keto, vegetarian, vegan etc, as long as you stick with the calorie restrictions.

Days to fast:

Sundays and Wednesdays (after the weekend and thought we’d try spreading the days – recommended they should be non-consecutive days anyway to prevent tiredness – so it doesn’t feel like we’re restricted). Although this could change depending on how we feel.

It is advised to try and pick days that will not be affected by events/work lunches/meeting friends etc.

It is not necessary to fast on the same days each week however it seems to be much easier than “winging it”, you can plan properly for the fasting days and also, you are less likely to skip a fast if you stick to a routine. It may help to choose days that you are particularly busy – these are usually the days that you think about food and eating less often!

How to fast?

Once you have chosen the days to fast, you need to make the decision of how to fast.

Preparation is key with this, if you are unsure how your day is going to pan out food wise then you are more likely to consume too many calories. You could choose to eat 3 small meals a day, perhaps 160kcal-200kcal per meal or maybe you’d rather have 2 slightly larger meals at 250-300kcal each, some even prefer saving all the days calories for 1 meal – maybe a late lunch or evening meal and of course there’s also “in between” versions of all of these.

As weeks progress, I will attempt to try these different alternatives to see how I feel and decide which method I like best.

I will try:

  1. Strictly splitting the calories equally between 3 meals (~167kcal per meal for me, ~200kcal per meal for my husband)
  2. Strictly splitting the calories equally between 2 meals (~250kcal per meal for me, ~300kcal per meal for my husband)
  3. Consuming all the daily calories in just one meal (500kcal for me, 600kal for my husband)

Consuming the calories in 1 or 2 meals in a day (depending on the timing) also includes another fasting technique – the time restricted eating, otherwise known as eating windows.

The success of sticking with this diet lies with the fact that you can eat whatever you want on 5 days a week, and in fact there aren’t any “rules” in terms of what to eat on the 2 fasting days either – just stay within the calorie limits. If you want a personal fasting day calorie goal, see this link https://thefastdiet.co.uk/how-many-calories-on-a-non-fast-day/. It uses your Basal Metabolic Rate (BMR) and activity level to calculate your total daily energy expenditure, your fasting days should consist of just 25% of this number. [The recommended 2000kcal for me and 2500kcal for my husband is not too far off for us]

First day of fasted eating (Heather 500kcal, Matt 600kcal split evenly over 3 meals)

I felt fairly ok with the first day of the reduced calorie intake, probably because I have kind of primed myself with the previous 24 hour fast and Military Diet. Matt however, felt extremely hard done by! He was hungry and desperate for the clock to turn midnight so he could eat something (not really the point of the diet, I persuaded him to go to sleep instead and made him wait until the next morning!) Neither of us felt particularly hungry when we woke up, we happily waited until showered and dressed for breakfast rather than rushing to the kitchen to eat whatever we could get our hands on. Let’s see what happens after the second day of restriction…

Second day of fasted eating (Heather 500kcal, Matt 600kcal split evenly over 2 meals)

It seemed more satisfying to have 2 slightly more substantial meals (compared to the 3 meal split), I wasn’t overly hungry until after dinner (it probably didn’t help that I baked some rosemary and olive sourdough and the smell made me want to eat the whole lot – I didn’t!). Matt struggled more today, missing breakfast meant that the salad for lunch didn’t really touch the sides, he tried to power through but we opted for an early dinner (added a bit of rice to Matt’s – we’re upping his fasting days to 800kcal, 600kcal just isn’t enough for him to maintain concentration!) Hungry towards the end of the night… to sleep and looking forward to breakfast!
I would have loved to have added some nuts and seeds to the salads on fasting days but unfortunately that would have blown the calorie limit out of the water so I’ll save those additions for non-fasting days (added bonus is that they are fantastic nutritionally!)

Third day of fasted eating (Heather 500kcal in just 1 meal, Matt 300kcal breakfast and 500kcal dinner)

Urgh! I don’t like this… coffee and water throughout the day until my one 500kcal meal early evening – not for me. I feel so much better eating more regularly so this would not be a long term option for me, the paella however was pretty delicious! 😊

Hints and tips

  • If you feel hungry when you first start out, stick with it – with the reduction in calories, it is totally normal to feel hungry or a little light headed but if this continues, have a snack and re-think whether this is for you – consult your doctor if you remain unsure.
  • Choose nutrient dense foods on the fasting days – think fruit, veg, fibre and protein to increase satiety and to make sure you get plenty of vitamins and minerals.
  • Consider using caulifower rice as an alternative to white or brown rice – it gives you a similar texture as an accompaniment to make a meal feel more complete with fewer calories. [25kcal per cup vs. 218kcal per cup of cooked brown rice or 205kcal per cup of white rice]
  • Think of eggs as a good low calorie protein source as well as greek yogurt and berries, grilled fish or lean meat.
  • Remember your drink calories count too! Stick with water, and drinks with zero calories, black tea and black coffee.
  • Try to avoid using your calorie quota on sweet or starchy foods, such as cakes, bread, pasta, rice, processed cereals and potatoes, and avoid alcohol too (every calorie counts!).
  • If you’re looking for weight loss… DON’T GO CRAZY ON THE NON-FASTING DAYS
  • Use a calorie tracking app such as MyfitnessPal to keep on top of your calorie goals (even if you spend one long session planning out meals using the app while meal prepping then you have the calorie counted meals ready to go and don’t have to think about it as much)

Energy levels 💯

Once we upped Matt’s calories to 800, energy levels were good. I was fine with in terms of energy for general day-to-day activities but I certainly wasn’t in the mood for any intense exercise… Getting my 10,000 steps in wasn’t an issue though.

Body changes 💪

We’re fairly consistent on our non-fasting days in terms of calorie intake – we do not over indulge so there was a calorie deficit over the week, so weight loss could occur if that’s the aim. I still felt like I had enough fuel to exercise (more so on the non-fasting days) so obtaining adequate protein for muscle building would be possible.

Side effects 😵

Hunger – we did feel hungry on the fasting days – I tended to be ok until I ate and then I wanted to eat a lot more hence I found it a bit of a struggle having 3 tiny meals but was better having the 2.

Ease 🤔

As long as you choose your fasting days well, as in days that you can be kept busy with work and have no social engagements or heavy exercise sessions planned, I think this diet can easily be incorporated into most lifestyles as the non-fasting days a not at all restrictive.

Cost 💰

This is not an expensive diet, you may even save money because you are eating less on 2 days a week!

Was it enjoyable? 🙌

I quite like it – one thing I do really like is that although calorie counting can feel restrictive, it does really make you think about what you’re going to eat so you can try some things that you maybe ordinarily wouldn’t think to make – I do enjoy cooking and trying new things out though.
All too often home made salads seem to consist of just lettuce, tomato and a bit of cucumber… Beetroot and feta for the win! 😉

Would I recommend it 💭

If you’re after a sustainable was to lose a bit of weight without a lot of restriction, the 5:2 may work for you. There are a lot of other benefits but as yet we have been following this for such a short amount of time, so cannot say whether these were apparent for us – I didn’t especially feel any different but I think that can be seen as a good thing given the calorie restriction – because the days were split up it was much easier to deal with. I would definitely suggest upping the fasting days to 800kcal if you don’t have a lot of/any weight to lose to ensure you have enough energy for it to not negatively impact your day. It does take a bit of planning but once you have chosen your meal split, you can do a bit of bulk planning and preparation so you’re good to go come fasting day.


More recently, Michael Moseley has altered his choices on this regimen slightly, although he still fully supports the plan, he has increased the calories consumed on the fasting days to 800. Studies on rats guided the initial 500-600kcal recommendation (as there were no human trials at that point. Further science has lead to the 800kcal mark being low enough to trigger desirable metabolic changes but high enough for people to stick to longer term.

Others protocols to look at

  • The VERY FAST 800 (for rapid fat loss – for those looking to lose a lot of weight)
    800kcal EVERY DAY. It is recommended that if you are going to try this that you should try for 2 weeks, if you hate it – STOP! If you feel good, carry on for up to 12 weeks. (Research is limited beyond that length of time) – it is based on a Mediterranean style diet.
  • The Fast 800/the new 5:2
    This is the updated 5:2, with 800kcal on the fasting days (it is based on a Mediterranean style diet)
  • The 5:2 Blood Sugar Diet – This is like the new 5:2 but focuses more on the non-fasting days being low carb (which tends to be a consequence of following the recommended Mediterranean diet anyway – just mind the pasta!) The fasting days are at 800kcal and there is no calorie restriction on the non-fasting days, just keep an eye on portion sizes.
  • 6:1 – just one day a week on the lower calorie fast, this may be more suitable for those looking to maintain weight whilst still getting the benefits of intermittent fasting.
  • Eating windows – 16/8 (Eat only within an 8 hour window, for example between 10am and 6pm each day) or maybe 14/10 (Eat within a 10 hour window)

Always seek medical advice before embarking on a new diet or eating regime. It may not be suitable for certain groups of people.


Paella recipe –> https://www.bbcgoodfood.com/recipes/smoked-paprika-paella-cod-peas
Spicy Mexican prawn and bean recipe –> https://www.slenderkitchen.com/recipe/mexican-shrimp-skillet