The Fast Diet: Eat 5 Fast 2

the fast diet recipe book

Anytime you put in the words “eat whatever you want,” somewhere in a diet plan you will have a best seller. In this case The Fasting Diet starts with that premise – for five days eat whatever you want, and for two days you “fast” – but not exactly, because you have 500 calories divided between breakfast and dinner if you are a woman, or 600 calories if you are a man.

The book, quite short, is packed with two kinds of references: testimonials from people you don’t know, and a selection of scientific research that shows the benefit of fasting.

The recipes for the fasting days are simple, easy to follow, and look delicious.  They make them look better with some lovely photographs of them.

The Science:

Almost any diet book that is read will have a group of scientific articles proving its point. They have become more sophisticated over the last 20 years as they will include research that has “insulin” and insulin-growth-factor. I shall save you the trouble and summarize the research for the following types of diets:

Fasting, Vegan, Vegetarian, Paleo, Mediterranean  Glycemic Index: all point to studies showing that insulin and the growth factor will decrease.  All will have studies showing that insulin and the growth factor are bad actors if there is too much of them (ask some poor worms).  All will show that they will decrease the chronic diseases of man from heart disease to cancer.

But I can do this:

Who doesn’t want to hear a diet with the words “eat as much as you want.” Pick one: the Atkins Diet was first to use this phrase — who doesn’t want a lamb shank for dinner, a dozen eggs for breakfast – until you get tired of it. Or, if you like Dr. Ornish, who doesn’t want unlimited lentil soup?

Eat what you want for five days, fast for two days (and it isn’t really fasting). Who can’t do that?


By fasting you utilize fat.


Personal testimonials


An amazing best seller in the United States.

Try it?

Yes, try it for a while. See how it does for you and if you like it. The science behind it- well, what is working for a few people may not work for you. But if it does, comment.

Like all diets – every single one: it works by you eating less. Just regulates it a little bit better. This gives you the time, and a regulation.

Who It Won’t Work For:

If you think on the 5 days you truly can “eat anything you want” then you are not going to succeed on this, or any diet. The people who provide testimonials in this book, and on television were in the modest range of eating. This meant their appetites were a bit overdone, and their lifestyle kept them overweight.

Obese patients- while they may try it, may find that this won’t work, and for them they will probably fail and ultimately need something to suppress their appetite (Lap-Band or gastric plication). Weight loss surgery is the ultimate way to loose weight, and if this diet is like every other diet in the world – it will work, but at the end of two years 98% of the people will have regained their weight.

Still, if you eat modestly, and don’t overdo it on the five days on, this diet might regulate it for you

What Should I do?

It isn’t worth the book price- you have the formula above- and if you have some favorite 500 or 600 calorie menu plans for the days you don’t fast – well, you are off and running.

But if you really want to loose weight– stop eating out, learn to cook and JUST COOK!

Dr. Terry Simpson About Dr. Terry Simpson
Dr. Terry Simpson received his undergraduate and graduate degrees from the University of Chicago where he spent several years in the Kovler Viral Oncology laboratories doing genetic engineering. He found he liked people more than petri dishes, and went to medical school. Dr. Simpson, a weight loss surgeon is an advocate of culinary medicine. The first surgeon to become certified in Culinary Medicine, he believes teaching people to improve their health through their food and in their kitchen. On the other side of the world, he has been a leading advocate of changing health care to make it more "relationship based," and his efforts awarded his team the Malcolm Baldrige award for healthcare in 2011 for the NUKA system of care in Alaska and in 2013 Dr Simpson won the National Indian Health Board Area Impact Award. A frequent contributor to media outlets discussing health related topics and advances in medicine, he is also a proud dad, husband, author, cook, and surgeon “in that order.” For media inquiries, please visit

Share this article on social media!

Latest Comments

  1. Demi says:

    Is there solid evidence that fasting can make everyone healthier and live longer?
    It seems like the majority of the science this is based on has been conducted on mice and rats, not on people.
    I want to know if fasting has any benefits besides weight loss and if there is any point in someone within the normal weight range to regularly fast for the rest of your life in order to be healthier.
    Basically, are the claims made in the book as groundbreaking as they’re made out to be, or is this just a good marketing scheme?

  2. thedoc says:

    This is a great marketing scheme. There is no solid evidence. There is conjecture, but it is like every other diet book:
    (a) tell people they can eat as much as they want
    (b) tell them studies show that insulin level is lower
    (c) tell them that it is anti-inflammatory
    (d) tell them that worms live longer on this diet
    (e) throw in some insulin growth factor, tell how it is bad, and then how the diet is good

  3. Rob McD says:

    I decided to try this diet five months ago after watching Michael Mosley’s original BBC documentary (long before there was talk of a book). I was not sold on the science behind it (there are more trials in humans than you indicate here but it still seems very preliminary) but it seemed to me like a very workable means of calorie restriction, and the health benefits of not being overweight are well established.

    Thus far I’ve dropped from the edge of obese (a BMI of 29.95) to the lower range of overweight (My current BMI is 25.92) and my weight is still falling steadily.

    Crucially, as compared to just about every other fad diet, I do not find this diet hard to do and see no reason ever to stop. I aim to reach somewhere around the middle of the “healthy” BMI range for my height and keep my weight there by varying the number of fast days accordingly.

  4. Stephen Callaghan says:

    You make it very simplistic and obviously haven’t even read the book properly, or as is more likely, don’t understand all the big words.
    Sure it isn’t for everyone but having dropped 3 trouser sizes (38-32) and lost 172lbs it certainly works. Judging by your photo you should give it a go!

  5. Anita says:

    I started this back in September after seeing it on TV on it. Previously i had been seeing a dietitian to help me shift weight as i have a lot to lose which though was working the weight loss was very slow, about 6-7kg in a year. One big obstetrical is that i cant exercise due to a medical condition so weight loss through diet alone is my only real option.
    Since September on this 5:2 diet i have lost 11.5kg. I have not felt bad on it at all, i dont feel like i am punishing myself and i am certainly able to ‘stick’ to it a lot better than you would think. Obviously you cant eat ‘whatever you like’ on a normal day, but if you do have a take away, eat some cake etc you dont feel guilty about it…you can do that! Seems though that it is hard to over eat too much especially the day or two after the ‘fast’ days, your stomach just cant take it, so maybe it is helping reduce stomach size along side reducing the calorie intake for the week?
    I dont care if it puts my body into repair mode or any of that stuff, i dont care if it has long term insulin benefits or any of that…i just want to get rid of a lot of weight and it seems, so far, to be doing that effectively.

  6. thedoc says:

    The science behind it is in his book, it is sparse to minuscule – but this diet can work for some. It won’t work for the majority of my patients who consume several thousand calories in a day. Your BMI of 30 meant you probably ate around 2200 to 2500 calories per day, or ate modestly, and probably did nothing for exercise. This decreased your caloric intake a bit, and allowed you some much needed regulation. The diet is not for everyone.

  7. thedoc says:

    Thank you for your kind words. There is always a testimonial for every diet from HCG to Atkins that will tell me because it worked for them that it works for everyone. \
    In research (where we use those big words) we call this “confirmation bias.” Meaning since you have experienced it, it must be true for everyone, and therefore this is a universal truth. Glad it has worked for you, however going from 38-32 is not dropping 172 pounds – you probably dropped to 172 pounds (which is more the size for trousers for the average height of a male). Chances are you were around 210 lbs or less when you started, which meant you needed a modest reduction in your caloric intake that you never managed to achieve without getting some regulation in your life, and now you have it. You never over-ate, and you certainly had minimal to no exercise – so this provided a way to regulate what you did. Of course, had you simply started cooking for yourself, learned good food and proper portions you could have done the same (as well as cut out the occasional fast food snacks). But I digress. My photo makes me look as if I can loose a pound or two? I must follow your suggestion immediately – or should I follow the fellow who said HCG works? No wait- I will do what many do with their avatars- where is a photoshop expert?
    Seriously, glad this has worked for you. It doesn’t mean it will work for everyone. My wife, who thinks she needs to loose weight (she is a size 4) is going to try this for a bit. I encourage it.

  8. thedoc says:

    I am glad it is working out for you – it is a regulation on caloric intake, and for all of my patients (and I deal with people who are morbidly obese) they need a plan.
    This isn’t a bad one – although you hit a nail on the head – “obviously you can’t eat whatever you like.”
    The vast majority of any weight loss occurs with what you eat, and perhaps when. Exercise is important, but without eating properly exercise simply doesn’t do it.
    I am glad you are doing well – because weight loss will make you feel better, it empowers you, and it seems like this has helped your journey- so congratulations!

  9. Stephen Callaghan says:

    You are right. I have lost 50lbs going from 222lbs to 172lbs. My BMI down from 33ish to 25.5.
    Apologies for the photo comment, it was uncalled for.

  10. thedoc says:

    That is a great weight loss! Good work. No worries – sometimes being on-line makes it easy to be a bit snarky, we have all been there. My wife, who is a size 4, wants to do this. Alas, when you marry someone in the tv business they just can’t get thin enough, especially after a baby. I think it is a good program for those who can (a) not overdo it on the five days – by that I mean more than 2500 calories and (b) need some planning.
    Curious- how do you feel on the non-fast days? Did you get through the idea of “overeating” on those days- what was the trigger?

  11. Ubizmo says:

    Why don’t you mention any of the actual research on intermittent fasting that is cited in the book? You mention studies on worms, but not Krista Varady’s human studies. These are obviously highly relevant. Your article states that the evidence for the plan is “personal testimonial,” as if there is no other evidence, but that claim is simply false.

    Varady predicted that on “feed days” subjects would tend to make up the caloric deficit by eating 175% of their normal amount of food, but the prediction was falsified. They tended to eat 90-110% as much. Isn’t this significant enough to mention?

  12. Rob McD says:

    I’m a 6’2″ guy who cycles to work (in Britain people do that!), so you’re a bit on the low side with the calorie counts, but more or less right.

    As has been mentioned elsewhere, you certainly can’t “eat what you like” on feed days, but the fact that you can get away with a pizza or a burger every so often and not have to worry too much does make it psychologically more attractive.

    I wouldn’t dispute that he diet isn’t for everyone, and as you seem to deal with the morbidly obese I understand that you have many patients who had much more of a weight problem than I ever had. Human beings are such a varied bunch that one size pretty much never fits all, but it does seem to be working for quite a few people, and that can’t be a bad thing given the current “obesity epidemic” that is all over the news. Whether it can last long-term any better than other diets of course remains to be seen, but I do feel that this one seems to have a psychological edge in the “do-ability” stakes, at least for me.

  13. thedoc says:

    The research is not there to back what this book says. In fact, the studies on aging and calorie intake have been debunked before (for a link to that you can see here). And most of the “research” is speculative, at best, when it comes to humans.
    In terms of what is “figured” in the book, or what is or not predicted – that awaits study. And, if it is like all diets that have been put to great tests – it isn’t that profound.

  14. thedoc says:

    Always happy when people find something that works for them.
    Obesity, and its epidemic, are a problem. There are two ways to handle it- but having cheap and abundant food isn’t one. What this book does that is good is:
    (a) Force some menu planning. We have to do this with our patients. The more they plan, the less they get in trouble
    (b) Doesn’t have depravation – two things never work in weight loss: shame and depravation
    The two additional pieces that we find work for lifestyle with our patients are

    (1) learning to cook for themselves. The ability to see and feel real food, get some great taste and cook has a profound influence on people
    (2) Tasting great food- not just bland, but great food.

    Exercise is great – and when I was in London I can see why you would cycle to work. Or take the tube. I miss that city, and look forward to my return

  15. Rob McD says:

    Luckily for me my mother is an excellent cook (Her cookery book collection rivals most libraries!) and I grew up with wonderful home-cooked food. This meant that as soon as I left home I was pretty much forced to learn to cook at least a few meals for my self, as it was the only way I could get food that I liked within a reasonable budget! I can only imagine what weight problems I’d have had if I’d been raised solely on junk food…

  16. Ubizmo says:

    You didn’t mention the alleged anti-aging claims in your article at all; odd to focus on them here. You did, however, claim that the “proof” is “personal testimonials.” As you must know, proof is hard to come by in science. There is, however, evidence from both animal and human studies that intermittent fasting improves cardiovascular risk factors. This is clearly relevant to general health concerns and goes beyond personal testimonial.

  17. Demi says:

    Could you repost that link? It doesn’t seem to be working.

    I agree, there is only a handful of studies that have been conducted so far on humans and these studies were only with small numbers of people. In order to gain credibility the results need to be replicated over and over again with large numbers of people ( in the thousands ) with various groups ( normal weight, over weight, young, old, male, female, healthy, with various health conditions ect) and all the results need to be pooled together in meta analisis to see what types of people it will benefit, if any.

    I think the best way to live a healthy long life is to eat healthy natural foods, keep active, stay slim and don’t smoke or drink. If you just eat junk food and fast twice a week im pretty sure your body will not be healthy as it is not getting all the nutrition it needs from fruit and veg and healthy foods, and that’s not good for you. There are lots of unhealthy skinny people, just because you’re thin does not mean you’re healthy.

  18. thedoc says:

    I do know science- and no, those studies are not terribly good, not repeated, and finally- had no effect on the outcomes of heart attacks or death from heart attacks. So what good is it if your HDL is a bit higher but you still have the same issues. Proof isn’t hard to come by in science- we have a hypothesis, we test it, simple formula. We adjust based on data, and we retest it anew. If we test something and it is positive, but no one else does, then we have an issue

  19. thedoc says:

    The calorie link is here:
    Diet and humans have a lot of issues – and for that check out my next blog (coming on this site later today).
    We live four score years and ten, or more, but my favorite saying: food can kill you, it can’t cure you.
    So, just cook– it is the best formula for a dull day

  20. Stephen Callaghan says:

    In August, when I started this ‘plan’ I probably overate by about 500 calories but now I have no problems with that as my body / brain tells me I am full much quicker. I try to stay around the 1500 / 2000 calories per day on non -fast days. I have one day a week blowout where I have curry carry out and beer. I think you need this to stay sane! I use the ‘my fitness pal’ app which has been a god send in keeping my calories under control.
    Just had bloods done and going back to the doctor in a couple of weeks in the hope my blood pressure which was about 160/120 has come down. Fingers crossed!

  21. thedoc says:

    Good luck with the blood pressure – but you may need some treatment. My fitness pal is good- we always recommend to our patients that they get a kitchen scale and weigh food they consume, this gives them a better idea of their portions.

Leave a Reply