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The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting

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Thousands of books have been written about the latest and greatest diets that will help people lose weight and improve health. But a key element in any successful nutritional health program is a tried-and-true method that most people haven't thought about—yet it could be revolutionary for taking health to the next level. This ancient secret is fasting.

Fasting is not about starving oneself. When done right, it's an incredibly effective therapeutic approach that produces amazing results regardless of diet plan. In fact, Toronto-based nephrologist Dr. Jason Fung has used a variety of fasting protocols with more than 1,000 patients, with fantastic success. In The Complete Guide to Fasting he has teamed up with international bestselling author and veteran health podcaster Jimmy Moore to explain what fasting is really about, why it's so important, and how to fast in a way that improves health. Together, they make fasting as a therapeutic approach both practical and easy to understand.

The Complete Guide to Fasting
The book also provides tools to help readers get started and get through their fasts, including a 7-Day Kick-Start Fasting Plan and healing liquid recipes.

304 pages, Kindle Edition

First published October 16, 2016

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Jason Fung

90 books1,371 followers

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Displaying 1 - 30 of 1,113 reviews
458 reviews13 followers
February 6, 2017
I started "intermittent fasting" last year after seeing Jason Fung's "Aetiology of Obesity" web series (available on YouTube). It made a lot of sense to me so I followed it up by reading his book The Obesity Code: Unlocking the Secrets of Weight Loss which mostly just recapitulates what's in the videos (but has all the usual advantages of books over videos). Since beginning IF, I've lost 50 pounds, easily, but I've noticed some people have a harder time with it than I do.

This is their book, really. Or yours, rather, if you find the notion of fasting intimidating. It pretty much matches my experience exactly: Eating is largely a psychological issue, not a physical one. There are obviously some caveats to that, such as people who are (literally) in a state of genuine starvation and undernourishment, pregnant women, children, and so on. But for most of us, most of the time, we don't need to eat, we're just used to eating.

The record for fasting is 382 days!

The real tips, for those having trouble, are to realize things like:

Even a little bit of fasting is better than none—our skinnier parents and grandparents used to do well eating "3 squares a day" with a 12 hour fast between dinner and breakfast, versus eating six times a day and never going more than a couple hours, while awake, without food;

Fasting just a little bit more is really easy. Just skipping breakfast (when bodies tend to be less hungry anyway) makes it easy to "fast" for 16-18 hours;

The more you fast, the better the results. There's no limit to the amount of fasting you can do: If you want more, you fast more (unlike, say, a diet pill or exercise or just about anything else which has a hard limit on how much you can increase);

Fasting does NOT make you tired, it does not impair your thinking, it does not weaken you, and this is pretty obvious when you think about it. If missing a meal (or two or three!) left you in a dull, weak state, the human race would have died out after the first brontosaurus (I know, but I'm on a roll!) escaped the hunting party.

Day 2 is the hardest but you can make the first two days easier with a low-carb diet.

The longer you fast, perhaps surprisingly, the easier it is.

The more frequently you fast, the easier it is. I don't even notice a 24-36 hour fast any more. I'm just out of the habit of eating. (And most of the eating I do now is social...well, with a few habits left.)

Critically, the benefits here are not limited to weight loss. Fasting reduces (or eliminates!) many of the symptoms associated with obesity and diabetes (type 2, especially, type 1 is trickier, obviously), but also is promising with some kinds of cancer, with Alzheimer's and a lot of other diseases.

On a related note, I discovered recently that the Charlie Foundation for Ketogenic Therapies, whose promotion of the diet for pediatric epilepsy saved my oldest daughter's life, has apparently discovered the diet also has applicability for certain kinds of cancer and Alzheimer's.

I think, maybe, the human body wasn't really designed to use carbohydrates as its primary fuel source. CHO seems to be a good way to pack on fat for the lean winter times, much the way hibernating mammals do. But we probably never evolved to have a lot of carbs, every day, all year 'round.

Where I diverge from the text:

I haven't done that much low-carb while fasting. When I have it's been successful, but it hasn't seemed necessary, at least not yet.

I still drink diet Coke. There's some concern that artificial sweeteners trigger much of the same body responses that eating does, so it may make fasting harder. I'd definitely cut it out if I were having trouble fasting. And I may cut it out anyway, but I don't find the actual evidence compelling.

The big one for me, not covered here, is sleep: I have found that I cannot fast if I am not sleeping. My oldest likes to wake me up at night sometimes (often consecutive nights) and when sleep-deprived, I either eat or go mad. So I've opted, mostly, to eat on those days, since going mad gets me in trouble with the Authorities.

Anyway, it's worth a shot, in my opinion, even if you don't need or want to lose weight. (Unless you're ridiculously low body fat, like 4%.) There are many time-honored benefits to fasting, not the least of which might be a reduced anxiety about "needing" to eat. Also, this is probably the cheapest, easiest diet you've ever had: It costs nothing and takes no time to prepare.

Check it out.
Profile Image for Negin.
629 reviews150 followers
November 27, 2017
I read this book a while back and since then, I have spent more time researching and thinking about it. I have also followed some of the advice, fasting off and on for 12-16 hours.

I’m updating my review. His first book, “The Obesity Code” was far better. At the time that I read it, I felt that it was among the very best of all the diet books that I have read. Below are some of my observations/the problems that I have with this book.

NOT ENOUGH TIPS
This book is not “a complete guide”. It covers a lot of background information and goes into great details about all fasting benefits and so on. The book is extremely repetitive when it comes to all that, really, really repetitive! Yet when it comes to actual tips and how to put fasting into practice, it is seriously lacking. So this is when I chose to join a few Facebook groups to learn more and to hopefully gain insight.

SEEMS TO BE MORE SUITED FOR CHILD-FREE COUPLES
When I first read this book, I thought of one major concern. I have to cook for a family and here is where the problem lies. I have seldom been able to lose weight when I cook for a family, but trying to fast and cook is torture! He mentions that fasting and cooking are not a good mix. I know that already. I fast once a year for religious reasons and I don't cook during that time. For me, cooking while fasting is simply not happening. He does have some short and simple fasts: 12 hour and 16 hour ones, but that's when the weight loss starts to plateau, as it inevitably does, he recommends longer and different types of fasts and I honestly can’t see myself being able to do that, unless if the entire family was on board. He mentions that fasting is most successful among couples when both commit to it, but not everyone is in that situation.

IT WORKS AT FIRST
From all that I have read and the little that I have experienced, when it comes to weight loss, this approach works initially, but then the amount of weight lost starts to plateau, and this appears to be more common among women. That’s when the author suggests that one needs to keep upping the ante and extending the length of the fasts.

EXTENDED FAST
I don’t have an issue with moderate fasting – 12 hours, 16 hours, the 5:2 diet, 3:4, and so on. What troubles me about the second book, is that they push for longer and longer fasts, in other words, extended fasting, which I think is simply unwise. I’m talking fasting for a week and longer, sometimes as long as three weeks! I think that that's too extreme. During that time, the daily caloric intake is well under 200 calories, when only water, kombucha, and bone broth are eaten. I cannot imagine it can be sustainable and how it can create a healthy relationship when it comes to food.

COFFEE
One thing that they do recommend is consuming large amounts of black coffee. I would not be able to tolerate that on an empty stomach.

HAIR LOSS
I was on the Facebook groups for a short while and saw that many complained about this. The idea of losing hair is not an appealing one. Drastic diets like this are known to be a major factor in hair loss.

MY FINAL TAKE
If you do wish to try intermittent fasting, I would suggest not wasting your money and/or time on this book, but rather only read “The Obesity Code”. If you read and re-read the tips there, that’s really all that you need. This second book really does not add much at all and isn’t worth the price.

Some quotes that I thought to share:

“Fasting, by taking a completely different approach, is much easier to understand. It is so simple that it can be explained in two sentences: Eat nothing. Drink water, tea, coffee, or bone broth. That’s it.”

“Try to physically remove yourself from all food stimuli during a fast. Cooking a meal or even just seeing and smelling food while fasting is almost unbearably difficult. This is not simply a matter of weak willpower. Our cephalic phase responses are fully activated, and to feel those responses without actually eating is like trying to stop a piranha feeding frenzy. This, of course, is the same reason you should not shop for food when hungry, or keep snacks in the pantry.”

“Interestingly, I’ve seen the highest success rates with husbands and wives who try fasting together: the mutual support is a big help and makes fasting far easier.”
Profile Image for Jessica Knutson.
Author 2 books13 followers
February 15, 2017
This book uses flawed studies and flawed logic throughout. The main argument is fasting vs. calorie reduction for insulin control. I think it's very lacking that they don't talk about HEALING insulin resistance through a whole foods diet, rather than just controlling it using a ketogenic diet. The authors claim to support a whole foods diet but include many non-whole foods in their approach, completely ignoring intact whole grains, legumes, and fruit, which all help to heal insulin resistance.

The book had a lot to offer, despite my complaints. I especially enjoyed the chapter on hunger. Here's a quote: "Hunger is a state of mind, not a state of stomach." It reminds me a lot of what Dr. Fuhrman says about hunger - what most people experience as hunger isn't true hunger, but rather "toxic hunger," the body withdrawing from the addiction to the food you eat.

I agree with the science behind fasting. However, it is not essential if you heal with the proper diet. Dietary intervention always works, especially with fasting. If you eat the way they advocate in the recipes of the book, you will feed the disease you're fasting to prevent - effectively undoing your work. That said, it's still extremely more healthy than the Standard American Diet.

Important to note: when Fung compares high fat to low fat diets, he is looking at flawed studies. In order to truly compare the two, he needs to look at diets where the fat content is less than 20% of the diet, a huge difference from the 28% "low fat" study he uses. And, most importantly, WHAT the carbs are that are consumed on this low fat diet (intact whole grains, legumes, fruits, and veggies).

Fung tries to bring in cultural tradition as evidence of the health benefits of a high-fat diet and compares how the Inuits supposedly have no disease prevalence in their society, the same as the Okinawan centenarians in their low-fat high-starch diet? For anyone who wants to look at that claim a little closer, I suggest this article: http://nutritionstudies.org/masai-and...

Just being nit-picky: he quotes Mark Twain twice - um, Mark Twain was an author who smoked cigarettes! He was not a health guru, and should not be quoted in a book on nutrition and healing.

For anyone who wants to truly prevent and heal disease, I recommend the book How Not to Die by Dr. Michael Greger.
Profile Image for Cindy Rollins.
Author 20 books2,153 followers
November 2, 2018
Good explanations of different fasting protocols. I am trying to do regular 16/8 fasting along with two days a week of 24-36 hour fasting. I do agree that it is easier to fast than to eat a little bit or be on a low calorie diet. I have made peace with using cream in my coffee and buying bone broth rather than making it. Oh, well! I was ever the rebel :) We will see how my body likes this new plan because I honestly never thought I would fast successfully and now I find it is not that hard. I especially liked the authors' acknowledgement that feasting is also part of the equation.
Profile Image for SVETLANA.
151 reviews16 followers
August 27, 2023
Fasting for days is interesting: no special diet, get health benefits and save money and time for cooking. But it didn't appeal to me. Intermittent fasting sounds better, but sometimes it interferes with the social life.

Of course, this book isn't only about fasting. It has a lot of interesting information about food and different diseases that can be cured by eating specific food.

I cannot say that the book is completely innovative, but as an additional source of information, it is satisfactory.
Profile Image for Carol Bakker.
1,207 reviews79 followers
July 30, 2019
I borrowed this from my library, and promptly bought my own copy. I had read Dr. Fung's book, The Obesity Code, in October 2017, but was shocked and dismayed at the last chapter when, out of nowhere, he sprung fasting as the answer to obesity as a hormonal disease, absent any practical advice. "It's really very simple. I'm not saying it's easy, but it's simple." I was exceedingly weary of slim men speaking pithily about simplicity.

However. I harbored secret ambitions to fast. And secretly tried. The problem was that by 11:00 a.m. I was jonesing for calories and often bought black licorice strings to get me through lunch. Still, I watched my friend Linda lose weight (currently 110 pounds gone) and reverse diabetes 2 and high blood pressure from intermittent and extended fasting. My friend Faith's face became chiseled in her Facebook photos (80 pounds less) after intermittent fasting. The irony? Faith got turned on to fasting after reading *my* review of The Obesity Code. :: wry grin ::

What convinced me, other than my friends' success, was this: it can't hurt, and it may help. Fasting is not for everyone. They list groups of people who should never fast. As it happens, I am not underweight, under 18, pregnant, nursing, or afflicted with GERDS. It's simple, it's free, it's convenient, it's flexible, it's powerful. If I feel sick, I stop fasting.

Although the book is helpful and convenient, all the information in it is accessible by reading blogs and listening to podcasts or YouTube videos. Dr. Fung will frustrate some, but I enjoy his no-nonsense demeanor and his creative metaphors. Megan Ramos has probably helped more individuals fast than anyone else alive; I heartily recommend finding her talks. (She also convinced my husband that fasting made sense for insulin-resistant people.) My favorite sections in the book were Chapter 9 on hunger and Chapter 15's fasting tips. In my all-or-nothing plunge, I've been gorging on fasting talks. The habit of fasting is custom built for all-or-nothing types.

A bonus for me was the recommendation to drink homemade bone broth. I already had a large cache in my freezer.

Does fasting work? In the long run? I hope so! I'm so reluctant to declare a thing, remembering my past forays in the One-Day Detox diet, WW, the Gluten-free diet, the HCG diet, the juicing diet, etc. etc. etc. Ask me in 2021.

My first fast [Friday night (6/8) to Sunday morning (6/10)] was the hardest. That was eleven weeks ago. Since then, fasting has become much easier and I've lost 22 pounds. Five of those weeks I was traveling and eating in a (modified and unmodified) celebratory manner. My weight was the same on July 24th and August 24th, but is lower now. I am buoyed by hope.

I'll close with a quote from Jason Fung:
The most important aspect of fasting is fitting it into your life.
Profile Image for Bianca.
1,083 reviews921 followers
January 23, 2020
I was considering not writing a review for this as I was sort of mocking myself for being so predictable and doing that very cliche thing at the beginning of a new year regarding diets and other self-improvements. The truth is I've been reading and watching quite a few videos on fasting and few other diet-related issues. That's how I came across Dr Jason Fung. I found his lectures extremely informative and very interesting while making so much sense.

If you have type 2 diabetes, pre-diabetes you must read his books, especially if you want to get off your medications and insulin. (No, I don't have diabetes, but I know a couple of people who reversed their T2 diabetes). Dr Fung's books The Diabetes Code: Prevent and Reverse Type 2 Diabetes NaturallyThe Obesity Code: Unlocking the Secrets of Weight Loss and youtube videos. What I love about what he preaches, besides the research-backed data, is that he's not selling any shakes, programs, "miracle" foods, pills. Yes, he wrote some books, but you can borrow them from the library or just watch the many youtube videos available.

This Guide is easy to read and it provides comprehension information without being too technical.

I guess now that I read the books, watched the videos, I just have to do it. Stay tuned. ;-)
Profile Image for April.
84 reviews2 followers
February 6, 2017
Fantastic read! In June of 2016, I took a good look at a photo of myself taken by a friend on a hiking trail. Despite my efforts to eat well and stay active, I was nearly 170 lbs---way too much for my small frame. I started a low-carb, high fat eating plan (LCHF) to get the weight off. After 7.5 months, and over 32 lbs easily and sustainably lost, I discovered intermittent fasting completely by accident. Wanting more info on how it works and the benefits of it, I decided to give this highly-recommended book a try. I cannot stress how much this helped me understand how our bodies work, why feasting should be balanced by fasting, and how obesity and type 2 diabetes don't have to be a scary light at the end of the tunnel. I wish I could put a copy of this book into the hands of everyone I love and value.
Profile Image for Shaun.
Author 4 books178 followers
July 13, 2019
Prior to reading this book, I knew a few people who had experienced positive results with intermittent fasting, which this book covers in addition to more sustained and prolonged fasts. I was curious about the science behind it as well as the basic recommendations and protocol. I also wondered if it might be something that some of my coaching clients could benefit from.

Prior to reading this book, my general feeling was that fasting, particularly shorter intermittent fasts might be a useful short-term strategy for individuals who had been overweight for long periods and/or were what I call "metabolically" sick from years of yo-yo dieting and less than ideal food choices.

Well, after reading the book, my gut feelings regarding fasting were confirmed. Fasting for short periods like twelve to sixteen hours, which essentially translates into eating only between 8 and 8 or 8 and 4, is probably a worthwhile short-term and even long term-strategy for not only losing weight but in maintaining that weight loss as it can assist with metabolic healing. In addition, it seems as if longer-term fasts (3-7 days and maybe even longer) might be a useful tool as well (at least in the short-term) for those who are obese or already have a metabolic issue like diabetes or metabolic syndrome.

That said, I am not sure this book is for everyone. I have a BS in Nutritional Sciences, a Professional Masters in Physical Therapy, and hold/have held numerous fitness certifications over the years. I've also worked with people across the lifespan with a myriad of physical and emotional issues. And in addition to my conventional professional training, I've spent over 2.5 decades taking additional continuing education courses and reading on my own. Basically, when I read this book, I read it with the benefit of a solid base from which to weigh and evaluate the claims being made.

And some of the claims in this book, while not necessarily untrue, are either misleading or confusing. He suggests that prolonged periods of fasting are not only safe but beneficial, which is a dubious claim. While it is true that in cases where someone has diabetes or is morbidly obese, the benefits of fasting may significantly outweigh risks, despite his attempts to reassure the reader to the contrary, there are risks. And yes, for the nutritionally savvy, fasting could be used to fine-tune certain systems, but for the average person??? I think the average person could take the ball and run right off the edge of a cliff. The author himself admits that with chronic fasting, in order to be effective you have to keep upping the ante. This should make one pause and take note.

So if you do read the book, read with some healthy skepticism, and if you do try more prolonged fasting (more than a day or two), make sure to discuss the benefits and risks with you personal physician.
Profile Image for Nate.
310 reviews1 follower
August 7, 2018
This book blew my mind! I hesitate to talk about it because there is so many minconceptions and fears about fasting. I had them. And I still realize how weird that sounds to say a book on Fasting is cool. I don't know what drove me to listen to this but now that I did... wow... just wow!

Imagine you were told that for work you had to attend an all day training on pencils. Can you think of anything more lame!?! I think if I were given this book as an assignment to read that would be my reaction. But then imagine seeing people come out of that conference before you went and all of them saying, "pencils are so amazing and I have to come back tomorrow to hear that again... I LOVE PENCILS!!!" That's how amazing this book is, it takes what appears to be an amazingly dull concept and makes it just amazing. I had no idea the depth and complexity the issue of fasting and hunger and how it impacts your health. If my yesterday self saw my today self. I would call myself a zealot, and my today self would just smile because my yesterday self had no idea!

Few notes... I would listen to this in audio. There is so much information packed into this that it helped to turn it into a lecture series rather then an intense study session. But, that;s me. There were several times I noted a timecode and went back to listen to it again just to make sure I understood it. The material gets dense at times.

Also, there are a few chapters you can skip if they don't apply to you. For example, I think one was called "Fasting for Diabetes" and I don't have that. I skipped finishing that chapter and a few others like it.
Profile Image for Katherine Owen.
Author 12 books584 followers
October 23, 2016
Best Book on Fasting & Why It works for Fat Loss & Curing Diseases

This is one of the best books on intermittent fasting and clearly explains why IF works for fat loss and curing diseases.

So, if you're overweight, obese, thin on the outside fat on the inside; or, you're pre-diabetic or type 2 diabetic already; or you have high blood pressure; or, you've tried every diet known to mankind, here is your answer: Dr. Jason Fung and intermittent fasting.
Profile Image for María.
144 reviews3,092 followers
March 28, 2021
Aunque he leído libros, libros y más libros sobre el ayuno sigo teniendo un montón de sentimientos encontrados. ¿Qué relación tiene con la cultura de la dieta? ¿Qué hay de los estudios que se contradicen entre sí? Es un tema que sigue pidiendo a gritos más investigación.

En cuanto a este libro en concreto, aunque hay bastante información también me parece que la bibliografía no está bien colocada y que hay estudios -muchos- de los sesenta, setenta, ochenta... Estamos en 2021 y no todo vale. Si se tiene que citar un estudio tan antiguo debe ser algo puntual y no generalizado. Sin más.
268 reviews6 followers
January 26, 2021
I don't agree with everything in this book. I find some sections to be overly repetitive. I question some of the charts.

So why did I rate this 5-star?

Because, for me, his methods work. This is where the rubber meets the road. This is the easiest and most effective fasting that I have ever done. I have done every kind of fast. I used to do a 24-hour fast (water only) regularly one day a week while I was at home with 3 toddlers. So I can tell you that the body appreciates the rest from digestion, my energy level was not affected, and I barely noticed that I was fasting. I have done an extended water-only fast in which an incurable condition disappeared from my body. At the end of that period, my body felt so good that I wished I did not have to eat again. I had seen the difference between how my body was supposed to function and how it functioned when I ate foods to which my body was sensitive. Of course, I did eat again. I was hungry. I am not stupid. :) But I am merely saying that sometimes the body needs a rest in order to get on with its task of healing. I did switch to more organic and nutrient-dense food and I did eliminate some foods completely.

Of course, if we ate as we were intended to, with only 2 or 3 meals a day instead of permanent snacking, we would be doing enough "fasting" and would probably never need to add a fasting program to our lives.

As a medical doctor, the author includes testing for markers to show how the body is improving through fasting. He has a program in which people can ease into fasting gradually and has the schedules printed in the book.

He offers "assisted" fasting in which people consume a fat in a hot beverage or some salted homemade beef broth to make fasting easier. He shows how this does not get the body out of "fasting mode".

And he shows you the differences in speed of results using each different method and time line.

He also encourages you to select one of his programs in which you can continue to take prescription medication and nutritional supplements.

And he tells you to use common sense. Let your body, not your will power, determine the length of your fast. If your body says to quit, then quit. Next time, you will go longer.

He also tells you that there are some people who should never fast.

I do disagree with his methods in some ways, for example, the recipes that he includes to help people begin eating after a fast. I cannot use most of these recipes because they include pork, nightshades, dairy, most fruits and all food with lectins. I can make substitutions because I commonly make them to accommodate my Type O blood. But many people cannot eat these foods without negative effects. So if they fail in this fasting, they might be failing for the wrong reason. They might be eating the wrong foods for their metabolic/blood type or foods to which they have sensitivities.

The major reason for fasting in this book is to restore health. However, as a side effect, people usually lose weight.

At one time, when I knew nothing about eating for your blood type or the 12 different metabolic types or lectins, I used the Hilton Head Metabolic Diet very successfully. However, I made my meals ahead of time and would eat the same lunch every day for a week. As the book said, I weighed myself every morning and had a consistent weight loss of between 0.1 and 0.2 pounds per day, always losing at least 2 pounds per week. But during the week that I ate chili for lunch, I had no weight loss. I was puzzled. I was following the recipes in the book. But I later discovered that chili has everything that I cannot eat (except for beef)--tomatoes, green peppers, chili powder and legumes. All of these foods have lectins which are harmful to many people who are Type O-non secretors. I omitted the chili for lunch and got on track again.

If I followed Dr. Fung's recipes, I would not lose weight and I would have pain in my joints.

So for some people, these recipes might not work.

I also think that he is not helping people get through the beginning stages of discomfort in initial fasts. There are many methods such as saunas and Epsom salt baths that help with the Herxheimer reactions of detoxing. He could have explained how getting rid of addictions (caffeine, sugar and simple carbs) before beginning fasting would make the fasting easier.

Fasting is not difficult. The body appreciates times of rest from digestion.

People might confuse the discomfort of withdrawal with the discomfort of not eating and quit. But if they were told to change their eating habits to remove most simple carbs, sugar, and caffeine first and transition to a high fat, low carb diet before the fast, then the fasting experience would be almost pleasant.

I am not saying that people should maintain a high fat, low carb diet constantly. There are many people much more knowledgeable than I am who are on both sides of this issue. I personally believe that, if we ate naturally from food available locally, we would be burning glucose in the summer to store fat for the winter and we would be burning fat in the winter. So we would not always be in ketosis. Ketosis happens in the winter months. Hibernating bears are in ketosis. But this seasonal eating pattern is simply my opinion.

I feel that people who use a high fat, low carb diet for a few days before they begin to fast will have an easier experience because, in fasting, after a few days, the body has to switch to burning fats because glycogen stores are consumed in a few days. It is easier, in my opinion, to switch to HFLC eating first, then begin fasting. It is easier to go through 1 change at a time.

I never expect to find a book that contains all the information on a subject. The author always must draw the line somewhere.

But I am glad that I read this book. Dr. Jung has opened my eyes to the specific healings that can occur in the body through fasting... and these are many serious, generally considered incurable diseases such as diabetes 2. He has made fasting much easier with the use of fats or broth in small amounts during a fast that will not switch the body from fasting to digestion. He has developed programs that help people ease into fasting and extend the length and frequency of their fasting.

I will be incorporating some of his ideas into my lifestyle permanently.

What more could I expect from a book? I am glad that I read it.
Profile Image for María Paz Greene F.
1,033 reviews184 followers
March 16, 2019
¡Al fin he terminado este mamotreto! Se me hizo más largo que la vida misma, pero creo que porque la gran mayoría de las cosas que dice ya las he leído en otros lugares.

Para personas que no saben todavía mucho del tema, este libro puede ser realmente bueno e interesante, porque junta los conocimientos todos sobre el fasting/ayuno. Yo que llevo un tiempo ya averiguando de esto, buéh, no lo disfruté tanto, pero aún así encontré que tenía que terminarlo. Además al final estaba ya acachada con el deber autoimpuesto (aunque los últimos capítulos fueron más divertidos), pero igual no quería que se me fuera nada.

Lo que significa esto para la medicina es maravilloso e impresionante, aunque las culturas antiguas jamás se alejaron de ello. La verdad es que yo me lo compro, todo. No puedo recomendarlo lo suficiente... pero es algo que hay que hacer antes que leer, para creérselo. O sea, que más que recomendar el libro, recomiendo el fasting mismo. Como método de curación y limpieza, y todas las cosas que aparecen aquí, allá y en la interné.

Este texto es un buen punto de partida, eso sí. Hay muchos que lo usan como una especie de biblia. Pero a mí no me rayó tanto (¡aunque es bueno!). Lo encontré MUY aburrido y MUY repetitivo, pero insisto que debe ser porque ya había leído antes de todo esto.

PD: Cuando digo "mamotreto" me refiero a "libro muy voluminoso", no a "objeto pesado e inútil", que es la otra definición. Claramente no es inútil, si lo fuera no le habría dedicado MESES de mi vida, jajaja.
Profile Image for Mehrsa.
2,234 reviews3,649 followers
December 15, 2017
Complete waste of time. Just a bunch of podcast people telling you why fasting is awesome. Read the Jason Fung book--the Obesity code, which is scientifically based. It's crazy to tell all people that they can fast for a week.
Profile Image for Nick.
93 reviews78 followers
May 5, 2021
Meh. This is the book equivalent of a Tel Sell teleshopping commercial for fasting. And more irritatingly so, not only for fasting, but for a ketogenic and/or Paleo diet as well. I hated the style of writing, and I don't ever use the word "hate" lightly. The voice of the audiobook narrator didn't help much either.

Some nice information here and there, but there is also some bad science and logic going on here. Leaps in logic, confirmation bias, cherrypicking, incomplete arguments, odd conclusions, etc. At times I just felt being manipulated by the writing style to believe what they say at face value, instead of digging into the subject meticulously and taking us along for the trip. Why would you use fallacies and (exaggerating) rhetoric when a subject speaks so much for itself? Why?! This has only made me take every claim and presentation of evidence with a grain of salt. And that grain had transformed into an enormous salt deposition, which could potentially be mined in the future to keep us prolonged fasters elektrolytically optimal, when nearing the end of this book.

I am disliking how much of the book is about the ketogenic and Paleo diet. Why are we reading so much about these diets, which are not necessarily the best diets overall, and/or a helpful choice for many of us? The book would have been so much better (and shorter) would it not have in part been a vehicle to promote the ketogenic/Paleo-diet. Yes, both fasting and ketogenic states result in ketone bodies. Yes, and? Both sexual arousal and panic attacks lead to a higher heart rate.

There are a lot of claims in the book, but too little or no evidence backing it up, and the writers mostly use anecdotal evidence and personal experiences to back up their claims and "demonstrate" how wonderfully it all works. I understand we need more (human) research on the effects of different fasting regimens, but I would have preferred a more humble tone. 

And what about these countless so-called fasting "All stars" who we are constantly meeting? In what way is this not redundant filler in the book to promote others' businesses and services? Why are we supposed to meet them all? Ok, to be fair, some of them were interesting passages or potential sources to check out, but most of them sounded like pseudo-experts selling a product, and echoing the writers' hyperbolic style of communicating.

"You would think that X would lead to Y? Well, think again!" Sentences like that. Brrrrr. Supposed benefits are repeated again and again. Annoying. There is a lot of "sciency"-sounding talk, but reads more like explanations from 50-year old Carol who did a course in metabolism and nutrition, and wants to tell her friend without a science background about it. "What is the solution to all our problems? Fasting, of course! The longer the fast, the better! Forget what "mainstream" science and medicine has believed for years and are still promoting, fasting is the way to go!" Argh.

Would have liked some more depth, and more clear science. Apart from the downsides of this book and my disappointment, fasting can be a great tool and overall it díd convince me more of implementing fasting regimens into my life. Also, the therapeutic potential of fasting for oncologists, sports medicine, endocrinologists, family doctors, and more medical specialists. There were arguments and conclusions in the book which matched the conversations by Rhonda Patrick, whose work I really admire, with several scientists researching fasting. These are better, more reliable and updated sources I'd recommend instead of reading this book, especially when you are interested in the fundamental science of fasting research. Or 'Fasting: An Exceptional Human Experience', by Randi Fredricks if you want a more cultural and broad overview of the subject of fasting.

I'll probably do a combination of time-restricted eating and occasional extended fasts, with a maximum duration of 48-72 hours. I have my doubts about the extra benefits of fasting longer than 72 hours. Eating a ketogenic meal or some bone/vegetable broth with lots of (micro)nutrients the day before and after the fasting window seems like an interesting implementation to try out, combined with an initial prolonged exercise of light cardio to quicken the breakdown of glycogen stored and speed up the time going into a ketogenic state. Some useful advice and practical tips throughout the book.
Profile Image for Cindy Marsch.
Author 3 books54 followers
October 8, 2019
This may be the solution for the Biggest Loser phenomenon! Remember how all the folks on that show regained their weight, as does almost every person who's lost weight?

After losing over 100 pounds, most of it with Bright Line Eating: The Science of Living Happy, Thin Free, I have struggled for over a year with regain (20 pounds) and hunger (most days, unless I'm gaining faster). But for six weeks I have implemented one or two 22-24-hour fasts per week and shorter eating windows resulting in 15-19-hour overnight fasts, plus lowered the carbs in my already-moderate-carb diet, and the weight is coming off, the first downward trend in 18 months. It's not so much that I'm reducing calories as that I'm fixing my insulin system--it seems I'm particularly sensitive to carbs and must keep myself burning fat instead. That's why I felt so good while losing 80 pounds in 16 months--I was burning my own fat. Then when I plateaued in a healthy weight range (but still overweight), hunger required more food, and my additions were mostly additional servings of starches and fruit, but with my well-established clear parameters. My body returned to burning carbs, and the insulin resulted in weight gain AND hunger at the same time.

I learned early in my experimentation with fasting that it's rougher when you're eating a lot of carbs, and having a lower-carb or even ketogenic diet makes switching back and forth much easier. I am now in talks and experiments with others like me (formerly morbidly obese, attained healthy weights, now battling hunger and/or regain), and we've gained the attention of some university researchers. I did most of my research via scientific papers and YouTube videos and websites with Jason Fung, Megan Ramos, and others like Stephen Phinney, Jeff Volek, Eades, Unwin, and Intensive Dietary Management, DietDoctor.com, Virta Health, etc. Most of the attention is on reversing the plague of diabetes, but those of us with great metabolic health while obese have a related problem--it's all about the insulin.

What's the solution for me ultimately? The jury is still out. Susan Peirce Thompson of Bright Line Eating says in her first Food Freedom video that "It's all about the insulin." I consider my current investigations an extension of that idea for those of us for whom BLE is life-changing but who need just another stage of help in the end. Could you skip BLE and go right to fasting and/or ketogenic diets? Maybe, but I've tried both of these before and stayed obese--BLE enabled me to establish a solid identity of health in a disease-producing environment--our food landscape. I'm now just exploring another area in the world of healthful eating for the 21st century.

Oh, and the book? I can just hear Jason Fung's distinctive voice throughout the pages. Though the book is beautifully produced with vivid colors, hefty feel in a pleasant squarish shape, and handy cover flaps for page markers, I'm surprised at some sloppy proofreading and a few of the graphics that are less-than-helpful while still striking to the eye. It's a great introduction to the principles and benefits of fasting, and it answers a lot of the objections. Some in the ketogenic research world caution against fasts over 24 hours, and some research I've seen suggests that despite Fung's arguments against it, there IS some detrimental protein (muscle) wasting beyond a few day's or a week's fast. Anyone on regular meds, especially for diabetes, should approach fasting ONLY with knowledgeable medical supervision, to adjust the meds on a daily basis as needed.
Profile Image for Kirstie.
38 reviews5 followers
February 12, 2017
Everything old is new again! Fasting is experiencing a resurgence as a therapeutic modality and it's well overdue and sorely needed in our heaving sickly world. This is not just another diet book.
It is actually anti-diet and clearly outlines how we can kick the asses of obesity, diabetes and other such modern day afflictions that are causing so much misery, illness and early death. Dr Fung has my complete respect. With intelligence, curiosity, and passion he has concentrated his life's work on solving the puzzle of why our current approach to weight loss and treatment of diabetes (calories in, calories out to lose weight...medication and insulin to treat type 2 diabetes etc) amounts to little more than blaming the victim when not effective, and is mostly just plain wrong. Better still he has nutted out what reliably alleviates these chronic conditions and is having success with thousands of patients worldwide. This book is clearly written and laid out, with solid relevant research, helpful suggestions and interesting anecdotes.
It discusses how we can safely and effectively introduce fasting into our lives and offers many reasons why we would want to. It answers common questions around the topic, addresses many fears and challenges all we think we know about what it means to simply stop eating for various lengths of time in the name of health and wellbeing. I've been waiting for this book without quite realising it, and I'm grateful for the author's efforts and excellent ability to communicate on the subject. Best of all he's not selling anything.. as stated fasting is all about subtraction and not about adding anything.
My only issue with this book is the rather lacklustre recipes at the end. Avocado chips? Egad!
Profile Image for Ahmad.
73 reviews6 followers
January 9, 2022
The complete guide to fasting is exactly what the tilte says. I have been fasting from last couple of years and it had changed my life for better.
I knew most of the stuff explained in the book already from my random google searches, but still able to find some useful nuggets from it.
Anyone can be benefited from some sort of fasting. From weight gain issues (it was my reason to begin fasting) to boost cognitive performance, preventing diabetes and many chronic illnesses.
Profile Image for Mehrnaz.
149 reviews93 followers
Read
April 24, 2021
چند نکته:
۱) از این کتاب به عنوان کتاب مکمل The obesity code یاد میشه.
خود کتاب شامل توضیح‌ و داستان‌های افراد موفق هست. من کتاب رو در حد خوانش سریع و ورق زدن برای به دست آوردن اطلاعات جدید، خوندم. اما داستان‌ها برام جالب نبود و مطالب توضیحی هم، مطلب جدیدی نداشت. قسمت‌هایی از کتاب، تکرار کتاب قبلی هست وقسمت‌های برای بیان فواید و نکته‌هایی برای فستینگ، که به نظرم برای هر کسی که کمی مطالعه داشته در این زمینه، تکراری هست. اگر بخوام فستینگ رو به کسی معرفی کنم، به نظرم یکی دو مقاله‌ی خوب در سطح اینترنت خیلی کافی هست و نیازی به خوانش این کتاب نیست.

۲) حس می‌کنم تعدادی از دوستان از طریق من با کتاب اول آشنا شدن و برای همین لازم می‌دونم بگم تعداد قابل توجهی متخصصین تغذیه‌ در ایران و خارج از ایران با این نویسنده موافق نیستند. و دلیلشون هم این هست که فانگ تاثیر کالری ورودی رو خیلی پایین بیان می‌کنه. برداشت شخصی من اینطور نبود اما وقتی یه سری متخصصی که نظرشون رو قبول دارم و به نظرم محقق هستند و براساس علم ، عمل می‌کنند، گفتند که کتاب‌های آقای فانگ رو توصیه نمی‌کنند، نظرشون رو پذیرفتم چون بنده هیچ تخصصی در این زمینه ندارم.
بنابراین شاید انتخاب کتاب‌های این نویسنده برای دانش تغذیه، بهترین انتخاب نباشه.
Profile Image for Martin Balaz.
125 reviews31 followers
April 19, 2017
Obsáhlý zdroj informací o jedné z nejstarších (a skoro zapomenutých) léčivých metod - půstu.

Věděli jste, že:
- Rekord v nepřijímání stravy drží v dobře zdokumnetovatelné studii jeden původně morbidně obézní Skot, který pod lékářským dohledem nejedl neuvěřitelných 382 dní a neměl žádné negativní zdravotní následky?
- Při půstu spalujete pouze tuky? Svaly jen v naprosto zanedbatelném množství.
- Půstem se dá lehce zvrátit zdánlivě neléčitelná cukrovka typu 2?
- Podle dosavadních informací by měl půst sloužit i jako účinná prevence vůči Alzheimerově chorobě a rakovině?

Jako fakt, půst je skvělá věc. Na knížce samotné mi jen trochu vadilo, že se v ní neřeklo vlastně nic moc nového, co už autor nerozebral v této přednášce na Youtube, případně na své webové stránce.

Pokud pořád váháte, doporučuju článek jednoho českého copywritera o psychologickém dopadu půstu zde.
Profile Image for Nick.
11 reviews
October 24, 2016
This book is complementary and overlaps quite a bit with Fung's The Obesity Code. Even with that overlap, I thought it was excellently written with some more information and details on Fung's theory for obesity and why fasting is different than low-calorie and other diets. It's an excellent book for someone interested in getting started with fasting.
I will be experimenting with some of his ideas in the near future.
Profile Image for Lisa.
430 reviews
April 27, 2018
This was a good primer about fasting and insulin levels when we eat. I don't agree with all of the author's claims. Call me old school but I still think and know for myself that calories in vs. calories out works.
Profile Image for Wendy.
215 reviews
October 17, 2018
I am an experienced faster, and in combination with a low carb, moderate protein and good fat lifestyle (no processed foods/sugar) I lost 25lbs and still able to keep it off for 2 years now. What Jason Fung shares in his books and on YouTube makes so much sense and I totally believe in fasting. But... I was guided through the whole process by a certified health practitioner. Intermittent Fasting for 12-15 hours is no problem (most of the fasting happens when you sleep anyway), but if you are thinking to try longer (water)fasts.... I think this is not something that one should do unsupervised. The other thing is "fasting for women". I am entering my menopause years and we have to be careful with our hormone balance. What I learned is that women should not fast 2 weeks prior to our mooncycle. This is the time our bodies need protein and carbs to make progesterone and lower estrogen. High levels of estrogen have been linked to other health issues. Again... I believe in the healing of fasting, especially with obesity & diabetes, but it is something to take slowly... step by step.
Profile Image for Michael Jones.
310 reviews53 followers
June 17, 2017
The basic concept presented here is simple, and incredibly powerful. People over the centuries have simply not had the availability of food that we have today. But our bodies are made to have times without food.

I have now fasted 5 times using the principles laid out here and it really is freeing if you have food habits that you can't seem to break out of or health problems. Wow!

This book is extremely informative with dabs of humor and excellent historical reflections. Big thanks to the authors for reviving a concept so needed in America today for health both physical and spiritual!
Profile Image for Jacqueline Wheeler.
531 reviews1,517 followers
January 3, 2019
Great, great book! It was such an easy read, which I really appreciate! I loved the whole concept, and will be sharing this book with friends and family. I feel like this just changed how I viewed the dieting world...
Profile Image for Srujan.
116 reviews48 followers
February 15, 2019
3.5 stars to be precise. It did help me get some clarity on fasting, but I was filled with too many numbers and charts for my liking. It probably is because I had a different expectation from the book and wasn't looking at Fasting from a scholastic purpose.
Profile Image for Rolando Gill.
250 reviews9 followers
February 23, 2018
So smart and self evident. Why didn't I think of just not eating? Great book. Highly credible authors with real world experience. Read it.
Profile Image for Paul.
52 reviews16 followers
February 11, 2020
Easy to read, great practical tips, and handy sample fasting plans.

I skipped some of the science in the middle about why fasting is healthy, as well as the section on the history of fasting (I’m a Catholic and a priest so I figured I get a pass). But I found all of the answers I was looking for to get me kick started on an intermittent fasting regimen.
Profile Image for Donna.
3,975 reviews54 followers
February 11, 2022
This is Nonfiction Health. I've read other books about IF and I think this is one of my top favorites. It went into great detail (in a good way) on the flexibility and different types of IF. I'm surprised other books said that their way was the only way....when there are actually multiple ways.....and you get to decide what works best for you.

This book had a lot of useful information to help the reader find success as well as how to tweak for optimal health results. So 4 stars.
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