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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4th Oct, 2013
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.
3rd Oct, 2013
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.
3rd Oct, 2013
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!
10th Oct, 2013
4th Oct, 2013
The "evidence" above is from that well known medical publication Glamour magazine!!!
2nd Oct, 2013
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.
2nd Oct, 2013
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
13th Jan, 2014
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?
25th Jan, 2014
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.


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