The Fast Diet – Michael Mosley

5-2 Diet – The Fast Diet Review:

As someone who has followed 5:2 now for a few months, I was really looking forward to the release of the 5-2 diet book. The Horizon TV programme was really illuminating and I’ve been doing pretty well so far using my own research and the advice of friends and other dieters.  And as such I’m probably NOT target market for The Fast Diet although I really did want to see how useful it was.  And I’ve tried to write my review of The Fast Diet objectively as if I was starting out because I suspect that is who this book is aimed at.

Michael Mosley’s ‘The Fast Diet’  isn’t a particularly expensive book and is currently available for at £5.99 at Amazon – personally as a die-hard 5-2 diet follower who has being using the fast diet now for 4 months I found some sections a lot more useful than others.  To some extent the book suffers because the diet IS remarkably simple.  Unlike diet programmes like Dukan, you don’t have to do different things at different phases or buy special food.  There are no ‘forbidden’ things to eat or things you must eat.  The only rule is to keep your calorie count to under 500 for a woman and 600 for a man on fast days.

The introduction gives a little more detail on Michael Mosley’s  original research and on his own test result pre and post trying the diet for a month.  It’s important to remember this diet is about a lot more than weightloss and it’s useful to have this point reaffirmed.  It’s informative and helpful and I can see myself checking sections as needed when friends ask me about the impact of the 5-2 diet on certain illnesses (I have no medical training at all!!!).  But, I found much of the ‘how to do it’ section of the book  potentially off putting.  The meal planning is all about eating breakfast and supper and not helpful for someone like me who seldom eats breakfast and hates boiled eggs (and elsewhere the book comments that a longer ‘total fast’ might be more beneficial). Equally the menu plans are less helpful for someone who wants to spread their calories over 3 meals.  But they do have the benefit of being relatively simple.

cauliflower + artichoke soup 5-2 diet

Some of  ‘how to’  is in my view unecessarily confusing and perhaps reflects the speed at which this book was published.  Nuts, for example, can hardly be counted as ‘good protein’, when to get your 50% of your RDA you’ll need to eat 578 calories worth. While, having tried my best to support my diabetic mother for several years, I know a reasonable amount about the GI and how important it can be, at times in this section you feel as if you are reading about the GI Diet rather than the Fast Diet.  Green vegetables hardly get a mention and most of the fish based meal plans revolve around oily fish; salmon, tuna and mackerel…which gram for gram have up to 3 times the calorie count of white fish.  While I’m aware that you should try to include oily fish in your diet regularly, surely this is better saved for days when you are not following a strict calorie regime?

Of course some of this may simply be that I believe those of us who are writing up the recipes we use ourselves for the 5-2 diet are doing a great job of coming up with interesting things to eat on fast days and practical meal plans.  But, there are things that perhaps could have been covered such as sensible options for ready meals for those who don’t want to cook. Personally I would have liked to see more about the different views about what to eat on non-fast days.  It seems to be a grey area, with some researchers telling us we need to keep an overall weekly calorie deficit – and for those who are aiming to lose weight with the fast diet,  I believe that’s an important thing to recognise.

5-2 diet chicken and aubergine stew with spices of Lebanon

At the end there’s a section which is simply quotes from people on the various UK forums with 5-2 diet threads.  Useful if you haven’t been following the forums anyway, rather wasted if you have.  Then, a simple calorie chart, a useful resource – you REALLY do have to weigh what you eat unless it happens to be a ready meal!

At £5.99 this is a sensible purchase if you are starting the 5-2 diet and would like a simple, one stop, resource and I’d recommend every 5-2 dieter gets hold of a copy to keep on the bookshelf.

I’m a real fan of the 5-2 diet.  It’s easy to follow, strikes me as being something I’ll be able to do on an ongoing basis and has health benefits as well as helping with weight management.  If I was starting on the diet right now, I think I’d find the book invaluable.  So, I’d advise any new 5-2 dieter to get hold of the book and read it.  My instinct at the moment is to skim read the GI information, as it makes what is a simple and easy to follow plan unnecessarily complicated and in some cases is just misleading.  And, don’t be disillusioned by the meal plans, there are, in my view, better options around!  Check out the 5-2 recipe section here. Karen has also being following the 5-2 diet for some months and has a great selection of 5-2 diet recipes – and if you are looking for veggie 5-2 recipe options, then pop over to Jac’s blog, Tinned Tomatoes.  Or take a look at Fiona Beckett’s hints for how to get through a 5-2 fast day.

Happy Fasting!

If you enjoyed this post, please consider leaving a comment or subscribing to the RSS feed to have future articles delivered to your feed reader.


  1. says

    Thanks for the mention, Fiona. Fair points – agree with a lot of them, especially the references to GI which are confusing if you’re unfamiliar with GI ratings. But I did find the science fascinating and it’s good to have the health benefits confirmed.

    • says

      Good luck to you on the diet. It was quite hard for me to be objective…I think I’ve been doing 5:2 for a bit too long so I hope I WAS fair;) I have no regrets about buying it though and it’s a very sensible price!

  2. says

    It was a good and fair review Fiona. I am waiting for my copy to arrive too. I didn’t think I needed it either, but was interested to have a read.

    Thanks for including me.

    Back to fast tomorrow after 2 weeks off.

    • says

      I’m doing a fast day today – it’s tough when you go back to it after christmas, but I always feel better on the day after! Trying Shirataki noodles again tonight!!!!

  3. says

    An excellent and very fair review and I can see the holes in the book already, as you mentioned so eloquently; I feel the book was a “rush job” and that may be reflected in some of the chapters.
    I have already ordered the book myself and look forward to receiving it.
    Many thanks for the mention and I feel delighted to be part of a very helpful group of food writers and bloggers!

    • says

      It was a tricky review, because I DO think none of us already well into the diet are the target market and it’s almost impossible for us to ‘unremember’ things and go back to what it was like when we all watched the TV programme and decided to have a go ourselves.

      For anyone new to the concept I firmly believe the book is the best place to start and for me it would have been great to have around 3-4 months ago!

      I almost feel guilty making any kind of criticism because the plan is rather life-changing for me and I am VERY grateful to Dr Mosley for researching and introducing us all to the concept.

  4. amanda carrara says

    Very interested to see this review. Watched the Horizon when first broadcast and was intrigued. Any way of seeing this again as it seems it’s not on Youtube or iPlayer. BBC should repeat it. Can any of the responders report on their progress in terms of health and weight, this would be very interesting. Thanks!

      • Sandra Villarreal says

        Good morning. I heard about 5-2 on GMA two days ago. Going to give this a try as I am in desperate need to find something that will work for me. I would like to lose 35-40 lbs. Mostly for my health. I have asthma and the extra weight does not help. I was wondering, how long did it take for you to lose 12 lbs. I am so frustrated with this extra weight.

        • says

          I am not a good example, because as you can perhaps tell I eat out a lot! But I have now lost 10kg (about 22 lbs) over 6 months, with a month or so break when I was travellling! I have another 6-8lbs to lose.

          I think I lost the first 6-8lbs really quickly, in the first six weeks. My weight-loss then slowed down a bit. But I eat out 3-4 times a week (sometimes twice in one day) as I am reviewing restaurants. I have also found my asthma is almost completely gone.

          If you do decide to have a go, please come and join one of the facebook groups. It’s really helpful to have other people…there are LOTS of nice supportive people there!

      • Lea Maur says

        I am into week three of the 5:2 and have not lost a pound? I can say with all honesty I have not cheated on my fast days and have usually fasted for at least 16 hours before consuming any of the 500 calories. Can you provide any insight? I haven’t found fasting the least bit horrible and am hopeful it might be a way to lose the 25 pounds I have gained in the last 6 years. Dieting and I just haven’t gotten along – I have never been able to do it. But this – I really want it to work. Any direction or suggestion is appreciated.

        • says

          As I’ve said before, I’m not a dietician, just someone who is sharing what works for me. I do know that if I drink any alcohol at all (even within my calorie limit) on fast days it doesn’t work for me, and also that if I eat a LOT on my non-fast days then it doesn’t work. I don’t lose but I also don’t gain. Some people in the FB group I am in also find that if they are cutting back too much overall (e.g. under 1000 calories on non-fast days), then that doesn’t work (theory being your body goes into starvation mode and stops metabolising). There are plenty of physical things that might stop you losing weight too – water retention or constipation for example. And there are also medical conditions. I take medication for a slow thyroid, and before that was diagnosed I gained 28lbs. I found it very hard to shift. Now I HAVE lost most of it (partly thanks to the 5:2 diet), but I still have 6lbs to go. I don’t think I’d be losing anything without the thyroid supplement though, without that my metabolism slows right down. If you have tried lots of diets and are still not losing weight I’d go and check with your doctor who can run tests!

        • Karen Knight says

          Just want to encourage you to continue w/ the 5:2 diet. My husband and I have been doing it for 5 months, with one week off for a vacation. There were periods of no change in our weights during the 5:2 diet. These periods lasted 3 weeks and later 6 weeks before we experienced more weight loss. The book averages the calorie intake for “average men and women”. Another way to calculate fasting day calorie intake is 25% of your “normal” daily intake. This was mentioned in the BBC show and the book, the FastDiet. There are formulas online to calculate that (based on height, ideal weight, activity level, etc.). So, 500 cal may be too much for some women, especially petite, less active or older women. We have also tried to increase our activity level, mainly walking, although I haven’t done so much lately. My husband is 6’2″ and started at 250lbs. He has done really well and is now 217 lbs. About 2 months ago he also switched to a 4:3 diet w/ modified fasting on Mon, Wed, and Friday. I only do it Mon and Friday. He is 62 yrs old and I am 58. I am about 5’3″ and now 116 lbs but started at 127 lbs. I like doing a small breakfast and supper about 12 hours apart. Usually I have oatmeal and frozen blueberries mixed in. It has gotten easier the longer we do it. Just don’t give up. I don’t normally post so I am sorry this is very late reply. Good luck.

  5. Mark Hutchins says

    Brad Pilons Eat Stop Eat book has been out for nearly 6 years advocating 5:2, its nothing new or revolutionary but your sure do get the results

    • says

      I’ve read some of Brad Pillons writings and in fact I’ve recommended him to people who are into sports nutrition and want to try intermittent fasting. I didn’t think his programme was 5:2 based, but I agree it’s been around for a while. I suspect though the popularity of Michael’s book is that it is more linked to overall health and weightlott than that kind of ‘gym body’ fitness. And that makes it just a little more accessible. That coupled with a medical background which helps with credibility

  6. Shawna says

    I have a question. I would like to try the 5-2 plan; however, do you have to cut the calories on the exact same days each week (ex: every Tuesday and Thursday) or can you vary it depending on what is happening during the week? Thanks for any help.

    • says

      I vary my days. I do try to space them out as much as possible, but I think it’s much better to try to do low calorie days when it works for you than to (for instance) give up a night out! That’s really why the diet works so well for me!!!

    • rk says

      I’m just passed week 3 and loving the fact its not become an obsession in life. I space out my 2 says depending on how my week pans out. But find it easier to do them on work days as I can get stuck into work and not think about food. It has made me think differently about food on the normal days too. Best of luck everyone.

      • says

        I think that’s why it works for me. I find I am far more conscious of eating healthy food on normal days and yet it doesn’t take over in that negative way that diets sometimes do

  7. Chris says

    Question; is 600 calories really fasting? Seems more like dieting two days a week. I suppose it’s better than gorging oneself seven days a week, but I wonder if you are getting the benefits of a “true” fast.

    • says

      apparently you do. The origination of the diet was some research from the states where they looked at the health benefits (rather than weight loss) of fasting and of cutting calories. They found that reducing your calorie intake to less than 25%-30% of your daily requirements (roughly 500 for a woman and 600 for a man) gave all the same health benefits. The original programme summary is and you can also find you tube clips of the whole programme if you search a bit. Notably, it wasn’t meant to be about weight loss…that is a side effect that for most people makes the concept attractive

    • says

      I haven’t stopped, but I have slowed down (some weeks I do 6:1). I don’t think you are supposed to stop altogether, it’s a lifestyle diet, so once you reach a target weight you should be doing 6:1 for maintenance.

  8. Isabel says

    I’ve just started the 5:2 diet and very optimistic. I need to loss weight for health reasons and when I watched the Horizon programme last year I was mildly interested. My husband then began to mention it and we both checked out various reviews etc. including revisiting the programme. This convinced us that this plan could work for us. We’ve both read the book and I’ve purchased the recipe book (like I needed another recipe book!!) this is our second fast day and we’re both still keen-good sign. I’ve never dieted in my life (I’m 63) and never really needed to until this past 5/6 years. I’ve always avoided diets as I really didn’t want to be obsessed for the remaining years! I’m totally sold on this way of life and your review Fiona and others comments have been encouraging. Thank you so much to all.

  9. julia scanlon says

    Hi, I am considering trying this. I am a little concerned however that Michael Mosely is given credibility as he is a doctor- I read in an article that he is actually a psychiatrist and therefore hasn’t a true medical background.That said I know that some research has been done on this and so am willing to have a go.

Leave a Reply

Your email address will not be published. Required fields are marked *