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

Author: Jimmy Moore, Jason Fung
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by Iowa_Dave   2021-12-10

I'm a big fan of Dr. Jason Fung who has written an excellent book on fasting.

He cites a study that talks about the benefits of 5-10 cups of green tea a day.

by ColeyColeyColey954   2021-12-10

I found this book super helpful. It led me to his website which also has a ton of the science references on extended fasting.

by cutercottage   2021-12-10

oooooo I am down to talk about fasting any day u/okaybutfirstcoffee!!

I can't recall what my longest fast was. 68 hours, something like that? I'm planning to do 2-3 day fasts regularly starting at the end of August.

I love Dr Fung's book, Complete Guide to Fasting. His blog is fantastic. This is one of my favorites because it explains the hunger cycles.

Regarding your question about weight loss, extended fasting is more effective because it ramps up human growth hormone. Basically the longer you fast, the more you reverse insulin resistance, and the more resilient your body gets. After about six months of doing OMAD most days, I now notice, for example, that if I have a "sabotage day" I just. can't. eat as much as I used to. I am straight up not hungry. Whereas before if I, say, ate a bagel I would be starving an hour later. I had one last Monday and I was so full I didn't eat again until dinner. Fasting FIXES your body and I fucking love it for that because I didn't even think that was possible.

by acconrad   2019-12-30
This is patently false.

Martin Berkhan created a very lucrative coaching platform with Intermittent Fasting:

And countless others.

by IridiumForte   2019-11-17

The heavier you are the longer you can go without eating. If you're a fat person (300lbs+) you could go a 2~ months safely without eating (without medical supervision being stressed, or else even longer), as long as you're drinking plenty of water. The average person could fast for a week or two np.

-I'm not a doctor though I did just finish reading this book last week

This book is written by a Doctor who's career has been based almost entirely on fasting, and runs the biggest 'fasting clinic' medical practice, located in Canada. A lot of his clients only eat one day a week.

by FriendofHolySpirit   2019-11-17

If you’re a teenager I’d do something small like a 1 day. There’s a great book if you want to read the science behind it‘s called The Complete Guide to Fasting

by neverhavearrivedhere   2019-11-17

Read The Complete Guide to Fasting. It'll answer all of your questions, with literature directly cited. It's the basis of most IF information.

by FriendofHolySpirit   2019-07-21

Regardless of what you think about Dan Mohler, check out Dan Mohler fasting on YouTube. He has some great messages. I also talk about it a bit here. if you want something quick to listen to first lol. I also recommend the complete guide to fasting by Dr. Fung and the r/fasting subreddit if you want to learn some scientific stuff on it.

The main things that I want to emphasize-

1- when you fast, fast with God not for him, meaning don’t do it as a work. it’s not something we have to do it something we get to do. His grace is available and you don’t have to get side effects-I don’t. But if you do, it doesn’t reflect on you

2-don’t worry about how many days you do. It’s the heart and why behind the fast that makes it count. Isaiah 58 and Matthew 6 have good things to say about fasting. Remember to read Isaiah 58 through the lens of what Jesus accomplished.

by FriendofHolySpirit   2019-07-21

Just remember, the stone has already been rolled away so we don’t need breakthrough, we have it.

Some background info-fasting surpresses the carnal voice in our lives and helps us to see clear. It helps us to learn that the “spirit is willing but the flesh is weak” is before Jesus died, and now that he died and rose again, our spirit is willing and our flesh says amen. Fasting gets rid of “cobwebs” so to speak and makes things clear. It’s truly amazing. The self control I have grown in from fasting is so awesome-it really changes your perspective on things. It teaches you not to live sensual and not to let your flesh be in charge. Not to mention the physical and health benefits from fasting. The important thing about fasting is that fasting and prayer must go together. With fasting we put off the old and with prayer we put on the new. I can’t even begin to talk about all the good fruit I’ve seen in my life with fasting. It’s truly a powerful tool God has given us.

I highly recommend you check out The Complete Guide to Fasting by Dr. Fung. It's a very informative book and has lots of great info on fasting. I do practice a fasted lifestyle and do extended fasting, I have a podcast episode here I did on fasting, if you'd like some spiritual tips.

For longer fasts, It's ok to take supplements when you fast-potassium, magnesium, and sodium are great. Check out the r/fasting sub, too. Lots of great info there :)

by FriendofHolySpirit   2019-07-21

No it’s not sinful to break a fast. God is happy that you’re even trying, a lot of Christians don’t fast even though the Bible tells us to. I believe there’s a difference between fasting with God and fasting for him, and when it’s with him, Grace is there to help you and to empower you. There is no way I could’ve done the fasts that I have except by his grace!

I have a podcast episode i did on it if you want the link message me. Give some tips on what is helped me. Most of all I recommend this book called The Complete Guide to Fasting written by Dr Fung. It’s very informative!

Also fasting is not to get something it’s to become someone. You’re already close to God by the Blood of Jesus. Don’t use fasting as works, it doesn’t get us stuff. It helps us to learn who we are by the finished work.

by DisplacedUser   2019-07-21

This book covers physical exertion a bit but great read.

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

by MNGopher23   2019-07-21

I think this contains just about everything you need to know in regards to fasting.


by FriendofHolySpirit   2019-07-21

I don’t have these things happen when I do extended fast. I would definitely start eating and if you’re going to do a fast like that again have a doctor supervise it. There’s also a great book by Dr. Fung called The Complete Guide To Fasting that I recommend

by FriendofHolySpirit   2019-07-21

For me personally, I don't prepare when I do fasts. I just do them. I highly recommend you check out The Complete Guide to Fasting by Dr. Fung. It's a very informative book and has lots of great info on fasting. I do practice a fasted lifestyle and do extended fasting, I have a podcast episode I did on fasting, if you'd like some spiritual tips.

It's ok to take supplements when you fast-potassium, magnesium, and sodium are great. Check out the r/fasting sub, too. Lots of great info there :)

by BenPoss   2019-07-21

read up

also freely readable here

but that might be tldr for you...

by garren   2019-06-02
I recently started a keto-style (high fat low carb) diet after reading a book on fasting [0]. I also picked up a ketone/glucose meter out of curiosity. Much as the book describes, fast for about 24-36+ hours and there's a good chance you'll be in ketosis.

After about 36 hours I've consistently measured 1.3-6 mmol/L. Between 48-60 hours I've measured around 4.4-4.6. As I understand it, anything above 0.5 is essentially ketosis. I agree with you in that, at least to me, there is a feeling of when you are in ketosis.

Ketosis is the generation of ketone bodies in the absence of glucose, ketoacidosis it the generation of ketone bodies despite the fact that the bloodstream is flush with glucose. Ketoacidosis is clearly a real concern, however as I understand it it's primarily an issue for type-1 diabetics.

This article feels awfully superficial, but I find the final statement, "maybe not being in ketosis isn’t so bad after all—now just cut back on the saturated fats", to be very reasonable.


by akurilin   2018-12-20
I usually go for 48-72 hour water fasts, IF has never done anything for me for some reason. Haven't tried much beyond 80 hours or so, mostly because I get bored of it. is a pretty decent resource on it.
by mateuszf   2018-12-03
I recommend this book - it's written by a doctor specializing in applying fasting.
by MeatheadMax   2018-11-10

> The fact we can survive something doesn't mean you are better for it.

What does 'better for it' mean to you, exactly? If extended fasting causes someone to move from morbidly obese to a healthy BMI, are they not 'better for it'?

> The people in studies that show benefits from intermittent fasting are still eating 800-1200 calories a day, and sometimes for just two days a week (the 5 and 2 diet).

Of course, IF is good for you, too. There are much less studies related to extended fasts, because people like you freak out and erroneously compare it to anorexia nervosa, which is a mental problem.

> The majority of benefits are blood sugar related (good for diabetics) and I've yet to see a study that suggests eating essentially nothing for a week straight is good for you.

Insulin resistance is why fat people are fat. Fasting to reverse insulin resistance will cause permanent changes to the way fat people process refined foods. This will cause permanent weight loss.

> The benefits of strict fasting are found in pseudo weightloss blogs, not in respected journals. That should tell you something.

Here's a 'pseudo weightloss blog' that is maintained by a doctor of nephrology (the study of kidneys):

Doctor Jason Fung is the leading expert on fasting for diabetics and overweight people. If you're interested in a nice, easy to read summary of the studies related to extended fasting, read "The Complete Guide to Fasting ".

Have you ever heard of the guy who fasted for 382 days straight? He consumed 0 calories in that time. He was monitored closely for the duration of the fast. You're telling me that it's unhealthy for me to fast for a week straight? "Prolonged fasting in this patient had no ill-effects." Interesting.

Honestly, the reason you don't hear much about extended fasting is because there is no money in it. No one makes money when you are recommended to not eat anything for an extended period of time. The reason the Standard American Diet is recommended in North America is because of food companies who paid doctors to lie to the public of 'the dangers of saturated fat'. This is why obesity is as high as it is. The human body is not designed to process refined carbs, yet that's 60% of the recommended diet.

If you want to see some info and studies on extended fasting, here you go:

by sovmen   2018-11-10

I don't know if I can give you the specifics you requested but people lose the weight and keep it off. You will find continuous calorie restriction typically does not keep the weight off. Doing that to your body is not going to increase your insulin sensitivity and it will significantly lower your metabolism (30-40%).

If you stay keto you won't have nearly as much water weight as SAD (carbs and water weight biochemically go hand and hand). Over super long studies people generally lose .5 lb/day. Someone much heavier than you would naturally lose more as it requires more energy to live in that body but your "real weight lost" should be >= .5 lb/day in a straight water fast.

You really can't go wrong with fasting. Something as simple as keto+18:6 is going to net results. Good results you can't get from SAD. I'd really suggest picking this book up and reading about the different protocols Dr. Fung suggests:

It'll give you a much better answer to all of your questions than some random on reddit can.