New 5:2 Diet Explained

New 5:2 Diet? Yes it's been updated and you're going to love the changes.

The original 5:2 diet was based around a two day fast each week where men consumed 600 calories or less on those two days and women consumed 500 calories or less.

The Science Behind the 5:2 Diet

The new 5:2 Diet. Updated for 2017 with more calories, science, tips and recipes. #vegetarian #vegan

The 5:2 Diet was created by Dr Michael Mosley, who introduced it to us in a 2012 BBC Documentary Eat, Fast and Live Longer

When Michael was tested in the documentary he discovered his body was a third fat which put him at a higher chance of heart disease or cancer. After he changed his diet and followed the 5:2 diet his chances lowered quite dramatically.

The scientific facts behind the 5:2 Diet

  • We all have a growth hormone called IGF-1. As a child this hormone helps us to grow, but as an adult it ages us. High levels of this hormone can increase our chances of getting heart disease, diabetes or cancer. To reduce our chances we need to lower this hormone.
  • An intermittent fast diet like the 5:2 Diet helps to lower this hormone and our bodies go into 'repair mode' rather than 'growth mode'.
  • This was found to be the case in scientific tests as well as studies of a small group of people in Ecuador who have much lower levels of IGF-1 and very rarely develop cancer and other age-related diseases.

A personal story

While I was doing the 5:2 diet I often spoke about it to friends at work and indeed a few of us tried it. During one of these conversations an Indian friend backed up the data about the benefits of fasting and how it helps present against disease. She said in India her parents, aunts, uncles,  grandparents, great grandparents and so on all fasted one day a week and there has never been any heart disease, cancer or any other age-related diseases in her family

The new 5:2 Diet

As I mentioned before, the 5:2 Diet has been updated. Michael Mosley is now suggesting we can eat 800 calories while doing the 5:2 Diet. In a article in The Telegraph he said “You don't need to stick to 600 calories. Cutting down to 800 calories a day seems to be almost as effective and for some people much more ‘doable’.

Tips for the updated 5:2 Diet

  1. Eat 800 calories or less two days a week
  2. Space out your fast days, don't do two together, this just makes it harder.
  3. To make the larger 800 calorie count work more effectively, eat dinner earlier the night before your fast and eat breakfast later the day after your fast.
  4. Try to stay within the recommended daily amount of protein while fasting. Many people eat too much protein and this limits the effect on the growth hormone. The recommended daily amount is 0.8 grams of protein per kilo of body weight. There is an online calculator to help you.
  5. Drink plenty of liquids on fast days. Water is best, but you can drink tea or coffee. 8 glasses a day is recommended.
  6. Try not to consume empty calories on fast days, so no alcohol (it's good for you to give this up a couple of days a week anyway), crisps, cakes or sweets. I have a healthy chocolate mousse you can try if you want a sweet treat and it's only 126 calories per portion. A square of really good quality of dark chocolate is a good option too, if you have that craving.
  7. Do a bit more exercise while following the 5:2 diet. Just walking more or climbing stairs instead of taking the lift can help. 

I'm going to give this a go. I followed the 5:2 diet when it was developed in 2012, then again the next year, but I found it was sometimes hard to get organised and back into it again after a break for a holiday or for Christmas and New Year. I lost 1-2 lbs a week while I was doing the diet and felt energised and positive on my fast days, but I found it helped to have a friend doing the diet too. If you don't have a friend doing the 5:2 diet, there are some supportive fast groups on Facebook.

Help with the 5:2 Diet

I have a great guide to the 5:2 Diet, with calorie counting, recipes and tips, but you can also find more info on The Fast Diet website. You may also want to read about Michael Mosley's new Blood Sugar Diet which incorporates the 5:2 diet.

If you have a 5:2 diet story or tips please share them with us.

For more support, tips and chat join the new Facebook community 5:2 Diet for Vegetarians and follow the 5:2 Diet for Vegetarians Facebook Page for recipes.


  1. I got into the 5:2 diet a few years back and enjoyed it but now I find I am riding more and not sure if I can do it on the days I do 1 hour of riding and the days I don't just get filled up. Sigh! My question is, does the 800 Cal apply to both women and men? and if so is there is a reason it is not different like it used to be?

    1. Yes, Michael Mosley says both can have 800. It has the same health benefits and if you have the earlier dinner the night before and a later breakfast the day after that helps with the weight loss too.

  2. Oh, my. We did the 5:2 for about a year - it was good, doing good things for our lab numbers (inflammation markers were way down, for example). The only problem with it was that I pretty much would be unable to talk to anybody without snarling at them, on Tuesday / Thursday. I basically had to say, "don't talk to me, it's a low-calorie day." Maybe 800 would work better ... we'll think upon it.

    1. I know it probay wasn't very funny but you did make me laugh. I think it's as much having a positive frame of mind as anything. If you arexresenting it, it's going to be bad.

  3. I lost 60lbs doing 5:2, and apart from the first week, I didn't actually feel hungry on fast days. I've had a break of a year and a half now, and I have maintained, partly, I think, because I generally do 16:8 almost every day.

    I'd like to now lose the last 30lbs, so if you want a 5:2 buddy, Jac, I'd be delighted if we could team up! xx

    1. Wow, that is awesome Nico. What an inspiration you are and yes it would be great to have a buddy doing this.

  4. Thanks so much for this Jac. I did the fast for about 2 years after it first was promoted and actually loved doing it (although I was very grumpy at times!). But as soon as I hit the menopause, I became ravenously hungry and seem to be unable to shed the pounds as easily. I sort of got disheartened and felt like I was losing a battle, so gave up! I have been wanting to try again with 5:2, as it did really work for me, but have struggled with the 500 calorie limit and have then just felt a failure.
    If 800 calories is now the permitted limit, then that sounds like a reason to try again!
    Thank you so much for sharing xxxx

    1. Hi Kate, Yes I did it for a while then too. I found it too easy to slip out of the habit after Christmas or a holiday. The new update will definitely be easier, but do follow the tips too.

  5. 8800 calories sounds much more doable. When I was doing it I actually had nothing but water and that worked really well for a couple of years, but then I started working from home - disaster. I've not managed to fast since! Something needs to be done though, so this is good news.

    1. Haha 8800 is way to much, I assume that was a typo and yes I am finding 800 much easier.

  6. 800 now! That is way more doable than 500. I think I am going to give it a go again. Two days a week, lots of veggies. Yes. I can do that. The last time I did 5:2 I lost 14 pounds but then never got past that.

    1. Yes it's much easier to do. Good luck this time.


I love reading comments, so thank you for taking the time to leave one. Unfortunately, I'm bombarded with spam, so I've turned on comment moderation. I'll publish your comments as soon as I can and respond to them. Don't panic, they will disappear when you hit publish. Jac x

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