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

Sign in or create your My Good Food account to join the discussion.
Mal Smith's picture
Mal Smith
7th Nov, 2018
This diet is the main suspect for my gout attack, the NHS web page on gout says don't crash diet. I'll be maintaining my weight from now on, or increasing as long as I remain in the NHS healthy range. Gout is the pits, worst pain ever, anything to avoid it in future.
Paul Jordan's picture
Paul Jordan
7th May, 2018
I feel 6:2 makes more sense; fast day 1, days 2,3,4 eat as normal, fast day 5, days 6, 7, 8 eat as normal. So, fasting 25% of time, eating normally 75% of time, one day on (fast), three days off, then simply repeat. So I guess it’s 1:3 really, in simplest terms. This has the advantages of even gapping throughout the 8 day cycle, plus you can fast additionally days 3 & 7 if you really need to get ‘shredded’, though I wouldn’t recommend this long term, just to hit target weight, bmi, body fat composition. I do 6:2 and find it perfectly sufficient for weight control. Also, as the cycle is rolling, I find compliance is improved. Hope this helps...
6th Oct, 2017
I agree, it's a bit of a misnomer, KayPeeCee.. The original 5:2 diet doesn't involve full-on fasting, just a couple of very low calorie days and five "normal" days. It's also a good idea not to go over the top on non-fast days,and to steer clear of the sugary, fatty stuff that possibly piled the weight on in the first place, although the odd treat can be fitted in on special occasions. However, in a variation which I often use, you go 16 hours with only fluids and then eat inside an 8-hour window. Or you can stay on fluids only for 18 hours and then eat within a 6-hour window. Another version is a 24-hour fast, e.g. breakfast to breakfast, lunch to lunch, or the one that works best for me, dinner to dinner. As well as water, fluids such as tea or coffee with a dash of skimmed or semi-skimmed milk are permissible, as are herb teas which don't require milk.
2nd Oct, 2017
I have heard a lot about this style of eating. Just a bit confused about the description though: fasting is not eating at all and only drinking water. This diet proposes restricted eating on 2 days, not actual fasting.
8th Dec, 2017
It works though. I find it easy to keep to and weight loss is steady while eating well. It's not a complete fast, because people would find that too difficult, particularly when working and using a lot of energy. On fast days I start the day with porridge and fruit, which lasts me until evening, when I have lots of salad with perhaps a 2-egg omelette or fish, maximum 500 calories for the day.
26th Sep, 2017
When it comes to diet, one size does not fit all. I started my weight loss journey two months ago and so far have lost 18lbs. I started eating healthier minimally processed food, avoid sugar and sugary drinks and have been drinking natural Tibetan herbs for slimming before main meals and for me personally it is the most effective weight loss combination.
23rd Aug, 2017
Sorry, Nodieting, but I beg to differ. After a lifetime battling with my weight and trying all sorts of diets, 5:2 works for me. Progress has been slow - I'm now in my fifth year having had several plateaux lasting up to five months, but I have shed over 20% of my starting weight and, most importantly, have not regained any of it. I could do with losing another 8-10 lbs, but I won't be too worried if I stay where I am. My previously high BP is now at a very healthy level, average 117/65, and there have been numerous other health spin-offs. I'm sure the clincher is the fasting, with which I have no problem at all. As others have pointed out, it's not so much a diet as a way of eating. I find that problems only arise if ever I overdo things, which usually means too much processed carbohydrates (it doesn't take much). A blessing in disguise really as you are unlikely to repeat the same mistake any time soon.
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
Clara Down's picture
Clara Down
17th Mar, 2019
Actually, one of the reasons the 5:2 diet is so effective is because it doesn't send your body into starvation mode! - starvation mode can only kick in after at least 36 hours of not consuming enough calories - and the breaks in between the fast prevent this from happening! This is why it's not recommended to fast for 2 consecutive days... do some proper research next time (:


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!!