What is the 5:2 diet?

  • By Roxanne Fisher - Health editor - bbcgoodfood.com

If you've ever considered following a weight loss diet make sure you have all the facts first. Our health editor and nutritional therapist take a look at the 5:2 diet...

What is the 5:2 diet?

What is the 5:2 diet?

Eat what you want five days a week, send your body to starvation mode for two. The part-time diet that still allows you to eat chocolate cake has hit the headlines and taken off in a big way.

The practice of fasting has been around for years, with tests carried out to uncover the potential effects as early as the 1940s. However, the dawn of 2013 ushered in a new spin on a practice that had more commonly been associated with religious rituals or even political protests. The intermittent fast, a weight loss wonder (with some other potential but as yet unproven health benefits) was snapped up by the UK dieting community who, feeling the bulge after Christmas 2012, were told they could eat what they wanted for the majority of the week and still lose weight.

The fasting for weight loss phenomenon was actually set in motion in August 2012, when the BBC broadcast a Horizon episode called 'Eat Fast and Live Longer'. Doctor and journalist Michael Mosley presented the diet du jour as ''genuinely revolutionary'' and as a result, published ‘the fast diet’ book in January 2013.

A month after Mosley’s book was published, former BBC journalist, Kate Harrison released her version titled ‘The 5:2 diet book’ The recommendations in both books vary slightly, though the general principles of the diet remain the same.


The dietScales

The simplicity of the diet and the fact you can eat pretty much what you like five days a week, are key to its popularity. Dieters are recommended to consume a ‘normal’ number of calories five days a week and then, for two, non-consecutive days, eat just 25% of their usual calorie total - 500 calories for women and 600 for men.

There are no restrictions on the types of food you can eat and it is suggested that women can expect to lose about a 1lb a week on the diet with men losing about the same if not a little more. 


Nutritional therapist Kerry Torrens says:

PlateThe 5:2 and similar intermittent-fasting diets are said to be easier to follow than traditional calorie restriction.  Fasting is a simple concept which appears to promote weight loss, although the hunger experienced can be a limiting factor for some. All the headlines for the 5:2 diet, and similar intermittent-fasting regimes, claim that calorie restriction may be linked with:

  • Living longer
  • Reducing the risk of heart disease, stroke and cancer
  • Improving cholesterol levels and blood-sugar control, and be anti-ageing thanks to its possible effect on lowering levels of the hormone Insulin-like Growth Factor -1 (IGF-1)

More evidence is coming to light, regarding the benefits of this type of diet although there is clearly a need for longer term human-based studies. 

As with all diets, pregnant and breast-feeding women as well as diabetics on medication, should seek medical advice before embarking on a restricted eating programme. Furthermore, this sort of diet can be unsafe for teenagers and children, who are likely to miss out on crucial nutrients needed for growth and may be at risk of developing unhealthy eating habits. The diet may be tough especially at the outset. On fasting days some report feeling low in energy, having poor concentration and experiencing headaches and dizziness. If you do choose to follow the diet, make sure that your non-fast days are packed with nutritious options, including fruit, veg, wholegrains and lean protein such as chicken, fish, turkey and dairy foods.

When you’re following a low-calorie diet, it’s important to make every calorie work – that means choosing nutritionally rich foods.

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

More information...

If you're going to give it a go, make sure you include our 5:2 recipes that are low in calories but high in nutrition.

If you want to read more about intermittent fasting for weight loss you can do so at:
The 5:2 diet book
The fast diet

Weight loss and good health can be achieved by following a healthy, balanced diet. Our nutritionist approved plan helps you find your perfect portion size, guideline daily amounts and nutritionally balanced breakfasts, lunches, dinners and snacks:
A balanced diet for women
A balanced diet for men

Want facts and information on other diets? Read more from our health editor and nutritional therapist on other popular weight loss plans:
The Atkins diet
The Dukan diet
The Paleo diet

This article was last reviewed on 25th March 2015 by nutritional therapist Kerry Torrens.

A registered Nutritional Therapist, Kerry Torrens is a contributing author to a number of nutritional and cookery publications including BBC Good Food magazine. Kerry is a member of the The Royal Society of Medicine, Complementary and Natural Healthcare Council (CNHC), British Association for Applied Nutrition and Nutritional Therapy (BANT).

 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 health care professional. If you have any concerns about your general health, you should contact  your local health care provider. See our website terms and conditions for more information.

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PrairieDog's picture

To Charlie686: 1. Good point about the Why. I suspect that you are right but would like to see more reporting on this. 2. Chocolate cake. The answer is that you can eat some chocolate cake AND healthy food. No one is suggesting that you can only eat chocolate cake. 3. True, 500 calories is not strictly speaking fasting, but it certainly FEELS like fasting, and probably many people do what I do, which is to truly fast for about 24 hours before eating those 500 calories in the evening of the "fasting" day. If you have brain-intensive work to do that evening, or if you want to be a reasonably tolerable spouse or parent, those calories can make a big difference.

I have been able to stick with something close to this system (more like 4:3) for quite a few years and I think it has more to do with my psychology than anything else. I'm not proud of this, but I find it easier to do things "all or nothing." It is easier for me to skip several meals and all snacking than to resolve to "eat just a little bit less" or to fastidiously count calories 7 days a week. Furthermore, there is good evidence that the self-restraint system, like a muscle, consumes energy and undergoes fatigue. Trying to exercise unceasing vigilance day in and day out is harder work (and more prone to catastrophic failure) than setting oneself a one-day target and then relaxing for a day or two; a never-ending marathon vs. a short sprint.

Charlie686's picture

The article starts by saying you can eat chocolate cake, then ends by saying you need to eat nutritionally rich foods on your eating days. So which is it? Also are the 2 days fasting days or not? If you're eating on your fasting day, then it's not a fasting day. But I think the key information that the article misses out, and why similar articles about dieting lack, is WHY this would work. WHY? Is it because fasting or eating limited calories forces your body to draw on its fat reserves rather than its glycogen stores?

silvia115's picture

Hi, You can eat cake on the days you don't fast, a slice, not the whole cake! The fasting is what works. On fasting days you don't eat any carbs so your body switches from burning glucose and carbs to burning fats. It's called ketosis. You can either eat small meals of lean protein and lots of vegetables (not potatoes, carrots, pasta, rice etc) or you can fast for the day and just eat dinner. I find that if I eat anything I get hungry while fasting all day and drinking lots of water works. I then have a normal dinner with my family avoiding carbs. The other days you can eat normally a not count calories. Of course if you make nutritious choices you will lose weight faster. I'm losing about .5kg a week and still have a glass of wine and ice cream every now and then. For those that find fasting difficult there is also 16.8 which means you fast for 16 hours including the time you sleep and then are allowed to eat the next 8 hours. This usually works out to mean not eating anything after your dinner, going to sleep, skipping breakfast and then having lunch and dinner. However you have to count calories for this method. You can find more information about this way of eating here


however be aware this is a way of life. It's so much easier than calorie counting and once you reach your goal weight you will still have to fast one day a week to keep the weight off. I've tried low calorie (1200 calories and exercise without success) this worked right away and I was told about it by a dietician. It works and depending on how strict you are with yourself on your fast days you can lose up to 1kg a week. However I am relaxed about it as I don't have much weight to lose. Good luck if you try it. :)

neeliew's picture

Just wanted to post that I have lost my baby weight on the 5-2 diet. I should add that my baby is a strapping 25 year old, so its about time! In those 25 years I've lost weight on various diets, but have never managed to keep it off. I started the 5 2 January 2013 and lost a stone fairly quickly. It took a bit longer to lose the next stone, but I'm there and never going back to size 16! The diet is hard to start with, but you soon get used to it and now is no problem at all. I look forward to tea and biscuits the day after a fasting day (sad I know). Plus I now have the occasional fish and chips, bake cakes and eat out whenever I want (not on fasting days of course!). I don't diet on holiday and find the few pound I put on easy to lose. I also do an exercise class on a fast day with no ill effects. Think this is a diet for life - hopefully a long one at that!!

RichNott's picture

A bit late but with recent diet programme thought I would add my experience. After the first couple of weeks I found this really easily. Ate loads and loads of salad and any low fat protein on fast day, often no dressing; I ate around midday and evening. Found exercise helped. I lost weight and it stayed off. Also felt more alive than ever; as if a mist lifted. Did it in preparation for an Op. Clearly everyone has to find something that works for themselves but this was one for me.

Would be nice to see some studies but as so much money is tied up I doubt we will; after all I just grabbed a bag of salad and sometime tomatoes and chomped away- not much scope for marketing.

robertdownie27's picture

I take 20 tablets a day. I take them four times after food. I don't think the 5:2 diet would be any good for me. I'm a 70 year old male and 13 1/2 stone and need to lose weight round my midrift, and can't exercise.

belllinda123456's picture

I concur about the effects of diet plans..They helps us to follow a routine healthy diet ,which are compulsorily beneficial.. In spite of it,if we focus on regular exercise and balanced diet, It will favorably works on all kinda weight's conditions like "weight according to height and body shape" ..I recently gone through the best diet plans(check out the link) .. I guess it favorably works for all of those who wanna loose weight .. http://www.thinreport.com/diets-plan

pmoseley's picture

If you eat a balanced diet full of fresh veg and fruit and fibre and restrict alcohol, fat and white carbs to a minimum, you should be able to eat as much as you want 7 days a week and still lose weight. I lost 2 stones in about 4 months that way and still have kept it off after 5 years.

johnjustice's picture

I feel the need to respond to some comments about the fast diet. The comments that bubbles night make need to be researched and evidenced. I am a male who clearly does not have the hormonal problems that may occur in certain women. It is right that these are raised and researched. I take issue with some of the comments made by your nutritionist Kerry Torrens makes in her views on this diet. It is correct that certain people need to seek medical advice before undertaking any form of dieting and that young people need certain nutrients to aid their development in their formative years.. However some of her comments seem to be without researched evidence and against peoples experiences with this diet. Many people find it quite easy to do. It is not tough at all. Most people doing this diet, according to the 5:2 forum do not suffer low energy, feel dizzy or suffer a lack of concentration on their "fasting days", quite the opposite and I personally do not suffer any of these issues, quite the reverse. "Some people MAY find it "tough". My fasting day ensures that I have protein and balanced carbs, albeit in a Ready Meal supplied from M&S who I trust in their description of their "Fuller Longer" meals. Fasting has been around for thousands of years in different forms. I am not being evangelical about this diet but having done it for the past 8 months with the odd dip I have had no negative side effects, on the contrary all have been positive.
Her comments seem to be all negative without having researched the all the evidence including the anecdotal evidence as supplied in some websites with comments from punters who describe their own experiences, the majority of which to me seem to be positive in respect of this diet. This diet, it seems to me has been developed in order that it is achievable by most people given that some for whatever reason it may not be suitable for or who may need medical advice before embarking on this fast diet.

Votadini's picture

Couldn't agree more with JohnJustice. I tailed off reading Kerry Torrens piece after the opening negative line which finished with "send your body into starvation mode for two (days)". I think most people agree, and it's being backed up with facts, that calling the two fasting days "repair days" is more accurate. Been on the 5:2 for 7 months and lost 13Kg and feel better than I have for years, I've even taken up badminton at the age of 52!
Torrens' article is littered with words like "claims" "unproven" etc giving it an imbalanced and negative view. I suggest the BBC wipe this article and give it someone to redo and who's done some research on a large group of people who are on the 5:2.

belindawood21's picture

My husband and I started this way of eating after watching the Horizon program. He never wanted to try dieting before, but at 59 his need to lose weight for his health became more important for us. We both started the diet in March and have both lost about 2 stone each, without much effort. It's great only having to calorie count a couple of times a week and even better being able to eat a little of what we fancy on the non fasting days and not worry over it. For those who find dieting tortuous this is a great way to lose weight and stay healthy.

colpeach's picture

I lost a stone on 5:2 diet in 2/3 months and found it easy. I felt great and still do 1 day to maintain it. Feel so much fitter and got lots of energy.

sarachinery's picture

I have been doing the 5:2 diet since February, I have lost about 8 kg in total. This is the first diet that I have ever followed as it is so easy. My weight had been creeping up since I hit 40. As a household on my diet days we all tend to eat the same with extra carbs for those not on the diet. Once I hit my target I intend to carry on doing the diet day once a week. I got used to doing it quite quickly and find it easier to do it on non-consecutive days. I feel less puffed when walking my dog and I am sleeping much better. Plus I can fit into my clothes again!

kath17's picture

The "evidence" above is from that well known medical publication Glamour magazine!!!

Lozzzy's picture

I'm a 5:2 convert. Although it's early days (5+ weeks), I view this plan as a wonderful revelation and a new way of life beckons. Luckily, I find the fast days easy too and look forward to the feeling of lightness and increased alertness the following day. I've got rid of 9lbs so far and 6 inches have disappeared. I do not eat 'pretty much' what I like on non fast days, I keep to a bit under my TDEE (check out the fast diet website for info). No more diets for me, just a healthy and sustainable attitude towards food. THANK YOU DR MOSLEY.

johnjustice's picture

I have been a 5:2 "Faster" since the beginning of Feb 2013 and have found this diet easy to do and stick to. I am a 65 yr old man and at the start of my Monday and Wednesday fasting days at the beginning of Feb 2013 weighed in at 15st 12lb. My lowest weight in August was 14st 3lb. I have fallen off the wagon, increased weight a little (8lb) then have started to take it off again. Now 14st 10lb and falling.
I find the fasting target of 600 cals easy to achieve. Low GI porridge and fruit for breakfast or lunch and an M&S "Fuller Longer" ready meal for dinner around 7.00pm. (I am lazy). Each fast for me lasts for up to 36 hrs including 2 nights sleep. I eat "normally" on non fast days. Sometimes "pigging out" resulting in weight increase, BUT.... eating normally on non fast days does ensure steady weight loss. The big plus is calorie counting for only two days, the other five just keep a weather eye on your eating habits. This works, I suffer no ill effects, I work out on fast days, 30 min cardio with no ill effects.
There is a 5:2 web site with loads of ordinary people posting their experiences most of whom have had positive results and who like the 5:2 approach to losing weight. That has become the focus of 5:2, weight loss, not inner health benefits as postulated by Dr Michael Mosley with weight loss a welcome secondary benefit.
I recommend the5:2 fasting diet to anyone interested in their health and losing weight. It is not radical, fasting has been around for thousands of years. Dr Mosley has made it achievable and easy to do. The only caveat is for those suffering certain illness or taking certain medications that may impact on their health should check with their doctor first. Having said that there are those suffering from diabetes who are taking this programme to heart according to the 5:2 website.

novices's picture

Please read my entry on this site and you will see that it doesn't suit everyone. I have also read elsewhere that increases in blood pressure are a common feature of participants. Unfortunately that was the case for me. However I wish I could continue this diet as it was the easiest and best for weight loss V normal eating I have ever tried. I am just not willing to risk a stroke for a diet, what do you think?

PathMan's picture

I am a 54 year old man who has recently taken early retirement. I was obese (15 stone 12.5 lb and 5 foot 10 inches tall) until I started the 5:2 diet three weeks ago. I have combined this diet with a reduced calorie diet on the other 5 days per week (1800 calories using the MyFitnessPal app). I now walk every day (typically an hour at 4mph, but sometimes more) and stick with the fasting two days a week.
I have lost almost 1 stone in 3 weeks and feel MUCH fitter and healthier. When I was working, I was troubled by asthma during the winter months. There has been no sign of my asthma this year (we are towards the end of January and I would expect to be suffering now), and I believe this to be an added effect of the lack of stress (giving up work) and my new healthier lifestyle.
I shall be keeping to the combined diets until I am down to a healthy weight for my age and height (12 stone 9lb target). Hopefully, I will reach this by September when I am 55 years old.