What is the 5:2 diet?

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

A selection of healthy foods with a tape measure

What is the 5:2 diet?

Eat what you want five days a week, dramatically cut the calories for two. The part-time diet that still allows you to eat chocolate cake yet lose weight 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 diet

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 1lb a week on the diet, with men losing about the same if not a little more. 

A woman standing on bathroom weighing scales

Nutritionist Kerry Torrens says:

The 5:2 and similar intermittent-fasting diets are said to be easier to follow than traditional calorie restriction, and an advantage is that you do not have to exclude any food groups. Fasting is a simple concept which appears to promote weight loss, although the hunger experienced can be a limiting factor for some. Many see the eating regime as less of a 'diet' and more as a way of life that can help them maintain their weight loss in the longer term. All the headlines for the 5:2 diet, and similar intermittent-fasting regimes, claim that calorie restriction may be linked with:

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 breastfeeding 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.

On fasting days some report feeling low in energy, having poor concentration and experiencing headaches and dizziness. Maintaining your hydration with water and herbal teas is important because dehydration can be a cause of headaches and tiredness. Include vegetables and protein on fasting days with some carbs in order to help manage and control your appetite. 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. Some participants choose to ease into fasting by first starting to extend the time between their evening meal and the first meal the next day – the gap the advocates of this approach suggest is a minimum of 12 hours. Avoid fasting on two consecutive days – instead break your week up, for example, by fasting on Monday and Thursday – this helps prevent tiredness.

When you’re following any low-calorie diet, it’s important to make every calorie work – that means choosing nutrient-dense foods. You are far better opting for lean protein like poultry and vegetables rather than calorie-counted ready meals. The latter may seem like the easiest option, but they are not as satisfying.

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. You may have read that emerging evidence is suggesting a beneficial role of fasting diets for the control and management of Type 2 diabetes, however, refer to your GP if you have diabetes or have any other long-term health condition.

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.

Weight loss and good health can be achieved by following a healthy, balanced diet. Find your perfect portion size, guideline daily amounts and nutritionally balanced breakfasts, lunches, dinners and snacks:
How to eat a balanced diet
A balanced diet for women
A balanced diet for men
A balanced diet for vegetarians
A balanced diet for vegans

Want facts and information on other diets? Read more about other popular weight loss plans:
Ketogenic diets
The dopamine diet
More popular diets

This article was last reviewed on 16 September 2019 by Kerry Torrens.

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

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.

Comments, questions and tips

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9th Mar, 2015
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.
31st Jan, 2015
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?
4th Jun, 2015
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 http://thefastdiet.co.uk/ 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. :)
21st Aug, 2014
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!!
19th Jan, 2015
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.
17th Feb, 2015
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
22nd Jul, 2014
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
10th Jul, 2014
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.
7th Oct, 2013
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
29th Jan, 2015
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.


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