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 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 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 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, 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. All the headlines for the 5:2 diet, and similar intermittent-fasting regimes, claim that calorie restriction may be linked with:

  • Improving brain function
  • 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.

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.

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 1 June 2016 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.

Comments, questions and tips

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17th Aug, 2017
Please excuse the spelling mistakes in my last comment.thanks
17th Aug, 2017
5,2 fiet isnt a good idea as those 2 days sending the body into starvation mode will only mske the body store fat when you start eating properly on the other daysanyone who does this is a fool and should research metabolism
4th Jul, 2016
The diet isn't really a diet, it is more like a way of eating - after I lost 15 kilos with the help of Dr. Simeons Diet and Anat Stern, I started doing sports and 5:2 dieting in order to maintain my new weight and keep fit, but I am fasting only 2 days per 2 weeks, because if I do more than I continue to lose weight, which I do not need anymore.
3rd Apr, 2016
I reached my target weight about a year ago but have continued to do the 5:2 diet, increasing my calories on the days I’m not fasting, and have maintained my weight. However, my question is – is it healthy to have a break for a little while or should I continue on the 5:2?
29th Apr, 2016
Hi stellahudgens. I am not a medical person but I do the 5:2 from time to time. Continuing research, mainly on mice but also limited research on humans does seem to indicate that fasting in the form of calorie restriction on at least 2 days per week as per the 5:2 "fasting diet" does produce both weight loss and internal health benefits that many other diets do not provide. If you have reached your target weight then I would suggest you go onto a "maintenance" programme of a one day a week fast but maintain a healthy diet regime the rest of the time without the need to increase calories on non fast days over your bodies daily requirement. By all means have a break if you feel the need, we are all different and you can easily return to this way of life at any time. In respect of the comments made by BarneyK the diet, far from being far fetched has its origins rooted in modern day scientific research. Any diet depends on the mental attitude of the individual doing it. Many people simply cannot do a daily calorie restrictive diet. Research at Newcastle University has shown that sufferers of type two diabetes can in fact reverse their condition normally within three months of following a restricted diet regime of 800 cals per day, not easily done but is achievable and medically proven. Each to their own, I find the 5:2 quite easy to do and having got the two {or three) days out of the way eat normally the rest of the time. The term "fasting" in relation to this diet was explained by its originator Dr Michael Mosley and simply means restricting calorie intake on fasting days to 25% of your required daily calorie needs to function normally so "fasting" does not mean going totally without food or drink in relation to the 5:2 diet. Accept that idea and you start to understand the concept.
8th Mar, 2016
This diet idea seems a bit far fetched. You're really restricting calories. If your normal weekly calorie intake is 17,500 (2500 cals per day times 7 days) but you consume only 600 cals per day 2 days of the week then your weekly calorie consumption is 13,700. That's really a 543 calorie per day deficit. So why torture yourself by only consuming 600 calories per day for 2 days? Just consume like 2000 calories per day and be a bit happier! The result at the end of the week will be the same...and you will lose weight. The best way to do this and not feel terrible is to consume a whole food, high fiber meal and keep the processed foods (refined sugars AND fats) to the bare minimum. I guarantee you'll lose weight and you'll be happy. If you eat whole foods, mainly veg, fruits, legumes and whole grains and if you want some meat very small cuts and VERY lean and limit full fat dairy you will lose weight and be a lot happier. Drink plenty of water but above all, keep the processed junk, especially junk fats: olive oil and butter to a bare minimum. When you eat a lot of fatty foods with carbohydrates the body will preferentially store the fat and use the carbs for fuel...which is what the body has evolved to do.
19th Jul, 2016
Some people see IF as a way of loosing weight alone. As shown on the BBC2 documentary its health benefits are very important. The body goes into full repair mode, something which doesn't happen a lot these days due to the grazing society we live in constantly consuming and snacking on food, digesting for most of the day. It is the hours of non-eating which bring the benefits. Low IGF-1 (insulin growth-like factor one), required when we are small and growing rapidly, not needed so much in adulthood; lowers cholesterol; lowers high blood pressure; creates new neurons in the brain; maintains muscle tone; increases Human Growth Hormone which keeps us young. So I view IF as medicine not just weight control, 2 days minimum are required to get full health benefits, not consecutive days.
1st Mar, 2016
I think you'll find that Kate Harrison's book was published before Dr Mosley's.
4th Feb, 2016
I have recently started the 5:2 diet again following illness and weight gain. I am a 67 yr old male. I go to the gym 3-4 times a week doing cardio and light weights and flexibility work outs. The 5:2 "Fasting" was a phrase developed to enable people to achieve the 500 or 600 cal target of twice a week, nothing more. You are free to eat what you want on Non Fast days, just dont pig out. The fast site forum has a system where you can work out your TDEE your Total Daily Energy Expenditure based on you, your life style weight etc. Try to stick close to that target on non fast days. Those on medication should seek medical advice but in general terms the Fast Diet should be ok for most people. Like many issues it is all about attitude, ie its all in the mind. Research, not just by Michael Mosley its creator but by other research scientists show that this type of fasting, over a period of time does have certain internal health benefits. Try it, it does work, and what will it cost you to do that?.
14th Dec, 2015
Having joined a gym 3 months ago and going there 4 times a week, and as a result having lost 5 lbs of body fat, there's absolutely no point doing 5:2 or 4:3 without undertaking some form of exercise. Yea, I get the whole point that what goes into your mouth dictates your calories, but you need to exercise as well. And before you ask, I'm 66, have a physical job and have never exercised before.


20th Jan, 2015
Will the 5.2 dieet help reduce a fatty Liver?
20th Jan, 2015
I have just been diagnosed with a fatty liver, I have started the 5.2 diet and a low fat one on non fast days, will this help?
2nd Oct, 2013
I am using the 5:2 diet - after watching the Horizon programme last year. Starting last year when I was "obese" in BMI terms and worried about potential health problems down the line. Am now in the normal BMI category having lost just over 50 pounds in about 14 months. I feel much much better - hardly surprising when I am carrying so much less weight around. I couldn't disagree more with the "nutritionist" comment above about the diet being "tough" and the supposed effects on fast days. OK the first few fast days are not easy as you are not used to just eating 500 calories a day, but you get used to it and knowing you are not on the diet the next day makes it doable. I haven't typically had any real problems on fast days, but make sure I drink plenty of liquids. Whilst I agree there are obviously some people who should not be dieting at all, the "nutritionist's" comments read as someone writing out the old, boring, standard, cover your back advice. As there is a growing problem with obesity/type2 etc, there needs to be some radical re-thinking - you can surely find more pertinent medical commentators to discuss using this diet (and some who have actually used it, maybe among the large numbers of the medical profession who are actually on it.)
1st Oct, 2013
Started this a few weeks ago and working a treat. Had an amazing Proawn Curry recipe for one of the starvation days http://www.bbcgoodfood.com/recipes/1929635/goodforyou-green-curry but it been removed!! Does anyone have it written down and can post it up?
novices's picture
13th Jan, 2014
WARNING!!!!!! Definately consult your doctor before embarking on any sort of diet! My husband and I were both following the 5:2 diet as per the book for a number of months (6 in all). We had to attend a hypertension clinic at our doctors because my husband was on BP (blood pressure) controlling tablets and I had been. To our horror we both had considerably elevated readings. This was checked and rechecked but found to be true. Our only life change since the previous year's check was the 5:2 diet. We both stopped immediately. It took four days for our readings to return to normal. I hate to think how long our BP readings had been elevated to a dangerous level, it could have been the whole 6 months. Thank goodness for routine checks!!