The 2-Day Fast

[Last updated 27th August 2019]

2-day fast

Recently there has sprung up a fad called the 5:2 Diet. The two-day fast is not to be confused with that.

About a month ago I was asked by a few people about this 5:2 Diet, and it sounded a lot like my own special fasting strategy.

But it wasn’t.

The 5:2 Diet is some adapted version made for weaklings, where you are “allowed” to eat 500-600 calories a day for two days of the week, and then eat completely normally for the other five days.

So, the 5:2 diet is not fasting. It’s just calorie restriction, and it’s vastly inferior to my 2-day fasting strategy for the following reasons:

  • The 2-Day Fast gives you a natural high.
  • The 2-Day Fast is a great exercise for Breaking out of Homeostasis.
  • The 2-Day Fast gets you ripped pretty damn fast.

The 2-Day Fast is a 40-48 hour period where you don’t consume more than circa 50 calories at a time, to avoid activating your digestive system.

For Beginners: Fasting 101

Note: If you’re new to fasting, here are three summary posts I’ve written about two of the most famous books about intermittent Fasting.

  • Part 1. Eat Stop Eat – 24 hour fast once or twice a week.
  • Part 2. Fast-5 diet – ca 5 hours to eat every day and 19 hours fast.
  • Part 3. My take on IF, bulletproof coffee and miscellaneous stuff.

I haven’t written a book on fasting, but I’ve done it for years.

Here’s my method…

Most people think that certain things in life are “set in stone”; they think hormonal levels are one of these things that cannot be changed.

I have good news for you: Those people are wrong.

You CAN change your eating patterns and how your body responds to hunger.

I speak from experience. I am never hungry (except after workouts).

This is great because:

  1. It saves me lots of time and money,
  2. It helps me stay lean,
  3. It makes me more productive and,
  4. It gives me much control over my behavior. . .

. . . (since I don’t have to think about food).

Is this hard?


It’s almost effortless because I’ve trained my body to go for long random stretches without food, and my hormonal levels have adapted.

How Eating Dulls the Mind

In your body there’s something called the autonomic nervous system (ANS) and the parasympathetic nervous system (PN).

The ANS has to do with being active and doing stuff, the PN has to do with resting and conserving energy.

Your body can only activate one of these systems at a time. 

Guess which system most people spend the majority of their time being in?

The PN.

When you eat you are activating the PN and it puts your body in a state of “rest-and-digest”, which makes you mentally lazy and demotivated.

–Just like a grazing cow.

"Because I eat all day I don't have to do any heavy thinking."

“I don’t have to do any heavy thinking, because I eat all day long, every day.”

The 2-Day Fast will snap you out of this daze in a major way!

You’ll be able to think MUCH more clearly.

The 2-Day Fast as a Way to Break out of Homeostasis

Fasting is a great way to practice your willpower because it involves an easily observable plateau, where you’ll experience an initial hunger phase.

This urge you’re feeling, which is telling you to eat, is triggered by your hormones–in order to keep you in homeostasis!

Homeostasis is the biological process by which your brain and body:

  1. Strive to minimize stress and maintain balance,
  2. Avoid change and save energy and,
  3. Flee from discomfort and pain.

When you go without eating for 16 hours or so, you’re breaking out of homeostasis, getting the body out of a rut.

If you aren’t used to it, don’t freak out. It’s a bit uncomfortable, but it’s only your homeostasis, wanting to return to its normal state.

–This is the #1 reason why most people fail with fasting.

Since they don’t know about homeostasis, when they try to change something in their lives–and it feels uncomfortable–they think it’s dangerous. . .

. . . and they stop and quit!

But it’s not dangerous, it’s just homeostasis playing tricks on the mind!

The discomfort is only temporary, in the transition.

Many people who have never fasted before react to this like they’re going to die from starvation, but the initial spike of hunger is completely harmless.

When you do it a few times you’ll know exactly what’s happening, and it becomes easy to mentally brace yourself against it.

Why Doing a 2-Day Fast is a Good Mental Practice

The 2-day fast is a great way to break out of homeostasis because you get feedback quickly. And it’s easy to see how your brain and body will try to fool you into quitting. It’s good practice because it’s so damn predictable.

This hunger-plateau is hard to overcome for most people because they trust their emotions too much–and now their emotions are telling them to eat quickly or something dangerous is going to happen.

You must brace yourself for this oncoming barrage of negative emotions and strange voices in your head telling you to stop what you’re doing.

These are the lies your brain and body tell you to keep you in homeostasis.

. . . And stop you from pushing your limits.

Your brain is wired for saving energy and remaining comfortable.

When you do a 2-Day Fast you break out of your usual rhythm–the homeostasis. The body resists it and puts up a little fight.

However, the resistance stops after a couple of hours, once you have broken through the hunger plateau, and your hormonal levels adapt.

I experience the hunger plateau around 16-20 hours. After 21 hours, like clockwork, it stops and I achieve a natural high.

The 2-Day Fast as a Way to Get Naturally High

When you don’t eat for a while your ghrelin levels (ghrelin is a hunger hormone) will increase, and this gives your brain surges of dopamine (the neurotransmitter of pleasure and focus), which makes you more curious while improving your ability to learn things.

–This makes reading and studying great activities while doing a 2-Day Fast.

I once sat and read a book about Napoleon for 24 hours straight, with the exception of bathroom breaks.

2-day fast

I don’t think I’ve ever been as immersed in a book as I was then.

Two things usually happen to me once I get through the hunger-plateau:

  • #1: Most notably, I experience an increase in cognitive and introspective abilities somewhere around the 20-hour mark after beginning the fast. This is accompanied by slight shivers as I slowly begin to get a bit colder. I also experience a tingling of energy in the back of my head.
  • #2: Following this, I start getting into an incredibly deep state of focus. I can feel my brain flex. My brain is now in an activated state for many hours to come.  This feels euphoric. It’s hard to describe it to someone who hasn’t experienced it. It’s like being curious about everything.

These sensations remain for a maximum of 48 hours (for me).

I’ve also done longer fasts (up to 80 hours), but I don’t particularly like it. I get weak and moody from doing it.

The 2-Day Fast is by far the most pleasant (and productive) fasting method, as it induces euphoria and increased focus.

The 2-Day Fast as a Way to Get Ripped

This one is a no-brainer.

If you don’t eat for 40-48 hours that’s a lot of time you spend in ketosis (fat-burning mode), effortlessly shredding unnecessary body fat.

I dropped from 77 kilos to 70 kilos in a 3 months by pulling 2-Day Fasts every Sunday through Tuesday. But then I stopped because it was too powerful, and I got scared–I didn’t want to lose more weight!

I still use do 2-Day Fasts occasionally, but not because I want to lose weight.

I might do it if I am busy and need to get things done. Or to practice breaking out of homeostasis to make sure my willpower stays strong.

How to Go on a 2-Day Fast:

Depending on how strong your willpower is, it’s going to be more or less easy for you to do The 2-Day Fast.

To make it easier you can:

  • Drink water mixed with glutamine (the most common amino acid).

I randomly found out–by experimenting–that glutamine makes longer periods of fasting much easier, without losing out on the beneficial effects.

Glutamine will not activate your digestive system, because it is absorbed in your intestines before making its way down to the gut.

–Just make sure you don’t go over 50 calories at a time (about a full teaspoon).

Glutamine is great for getting a healthier stomach and also for recovering from injuries or sicknesses. For years I had a nasty stomach disease–candida albicans–and my gut would swell up real big and get gassy. Doing 2-day fasts played a BIG part in curing that.

To make the 2-day fast easier you can also:

  • Drink coffee or tea however much you like.

When you combine coffee with the ghrelin-induced dopamine high that hits after ca 20 hours. . .

. . .You get into a state of fanatical focus and single-mindedness.

It’s great.

Recap: Why You Should Go on a 2-Day Fast

The 2-Day Fast is great because:

  • It heals your stomach by giving it time off when you’re not digesting food. (Most people constantly have food digesting in their stomach!)
  • It gets you ripped by switching on ketosis, burning fat effortlessly.
  • It allows for longer periods of hard work and immersion, as your ability to concentrate and learn things gets dramatically heightened.
  • It gives you a natural high, making you feel crisp and clear-headed.
  • It breaks the cycle of incessant stimulation, boosting your self-esteem and sense of personal freedom.
  • It is good practice for breaking out of homeostasis. Improving discipline, metacognition, and mind-body mastery.

Doing a 2-day fast is also good for knowing yourself better. You become better at detecting ways that your brain tries to fool you by means of rationalizations and excuses for why you should eat–and go against your decision to fast. And this ability isn’t just useful for fasting. . .

NOT QUITTING is a crucial skill for any type of success.

To make the 2-Day Fast easier:

  1. Drink about 5g of L-glutamine every 3-5 hours.
  2. Drink coffee or tea. They both suppress hunger and do not contain any calories.

 Common questions I’ve received about the 2-Day Fast


But, I heard fasting is dangerous, and that breakfast is the most important meal of the day?

I’ve heard that too. But it doesn’t make it true. It’s just clever PR and propaganda, made to sell you bacon and cereal.

How do I know if I break the 2-Day Fast and activate my digestion?

You will notice if you break your 2-Day Fast by consuming too many calories, because then your stomach will start to growl and you will get hungry again. You will stop feeling clearheaded, and will start thinking about food instead.

I am afraid to try fasting for so long because I don’t know anyone who has done it.

The stoics did it to practice their discipline. Benjamin Franklin did it. Jakob Walter and other soldiers often did it. And you can check out the comment section of this post for more people who did :-)

How much sleep do I need when I am fasting?

Less than normal.

I can sleep for 4-6 hours when I do a 2-Day Fast and feel fresh still.

Can I end The 2-Day Fast by working out?

I often end my 2-Day Fasts after 40-48h fast by drinking some coffee, creatine, glutamine, and heading to the gym. I usually lift for about 40-60 minutes. This is no problem for me.

I have also tried lifting weights to end longer periods of fasting (50-80 hours), but I find myself becoming physically weaker and fatigued. So I don’t recommend doing that.

Now do a 2-day fast and thank me later.

* * *

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  1. Gwyneviere says

    Hi I’ve decided (very spur of the moment) to do a 48 hour fast; a relief to know I won’t experience (I hope) a caffeine withdrawl headache! Is it ok to drink water with a squeeze of lemon or lime? Or best just to stick with tea, coffee and water? Thanks.

    • You would know by now.
      But it’s fine either way — you can probably consume 2 lemons/limes without breaking fast. At least I can.

      • Thanks. I only made it to 36 hours but for my first fast thought that was pretty good. I had a lot of energy after 24 hours but by 36 was feeling irritable and foggy. Had a light healthy meal. I will definitely make this part of my lifestyle and IF as well. I’m a middle aged woman and although I’m active and relatively fit, I don’t work out ( I know I should!). Do you think I should still take l glutamine? I appreciate your opinion. Gwyneviere

  2. Jim Demello says

    I am at 37 hours on my water and tea fast and feel – not hungry. But I am doing it to correct some health issues. Really appreciate your web site and the comments as they motivate me to continue my fast(s). I was able to compose a song and post a video in a really short time as my focus was exceptional during the fast. Fast on!

  3. Hi my name is Elisabeta and i been doing fasting for years now i start it with itermeding fasting then i went to 24 hours then i dit it 75 hours and today i just end it 48 hours of fasting i eat a meal was fantastic btw i only eat vegetate no milk or eggs u know what the comercial do so now i eat one meal in 48 hoursand then i going to fast for other 48 hours the benefits are clarity in the mental and the body regenerate him self and so much more i say that pplshould do it our ancestor dit it it only the moder society that is scare do do it ……Love …:)

  4. I have completed many 24 hour fasts and 9, 36 hour fasts.

    Is there a problem with fasting for 48 hours, eating one meal and then fasting for another 48 hours and so on? One meal every 48 hours.

    My gift to myself for Christmas, which is tomorrow is fasting for 48 hours. I have already started fasting.

    • I don’t know. I don’t think it’s sustainable because you would have to each such a big meal. It is probably not a healthy long-term practice due to stretching your stomach.

      Great gift: You’re a role model for frugality :-)

  5. Thank you for the article.

    I ‘ve been doing a 24-hour fast monthly for the past year and I really enjoy it, and part of me wants to try a longer one.
    However, my primary concern is my weight, as I am skinny (60 kgs to 175 cms, if i weighten any kilo less I would be officially underweight).

    So what is a benefit for many men (losing weight) is actually a side-effect of fasting which I desperatley want to avoid. But at the same time I like fasting and feel its benefits so I think I will give a try to the 48-hour one and see if by doing it once per month it’s going to make me lose too much weight or not.

  6. Hi. So the gist of the 2-Day fast is…
    Basically, we need to not eat anything for 48 hours except consume tea, coffee or water mixed with L-Glutamine (5g) anytime we like? (Not exceeding 50 calories during the fasting period)

    Also, I am overweight and I have started walking a lot to my school. Transport has become unavailable in the outskirts due to some issues temporarily.
    So I have to walk 6km a day.

    With that said, will the walking be a problem with the 2 day fast?
    It won’t interfere with it in any way right?

    That’s my only concern.

    – Nes-kun~

    • You have understood correctly with one exception: You can’t have 5g of L-Glutamine (anytime). You need to wait about 2-3 hours or so in between not to “activate” your stomach and stimulate hunger hormones (insulin, ghrelin, leptin, etc).

      Walking 6 km/day is great–it’ll give you a positive habit and surely help you think better as a side-effect. And it will not interfere with fasting.

  7. I found that the 2-day fast gets much easier around the 24-36 hour mark. It’s definitely worth trying at least once.

  8. I read “Eat Stop Eat”.. And it clearly states that you are only supposed to fast for 24 hrs . . or your body will kick into “starvation mode” aka storing fat! According to studies ..after your 24hr fast you must not fast for another 48hrs… Are you affiliated with that book? How do you say the opposite is true?

  9. Hello from Czech Rep. I do fast for 24 hours every day (dinner-dinner) and eat pretty low carb. I practice calisthenics 3 time a week and boxing 2 time a week. I want to burn this “last pounds” of stubborn fat, but I probably reached plateau. Do you think 48 hours fast once, twice a week can be beneficial?

  10. Isn’t Parasympathetic Nervous system a part of ANS (with ANS dividing on Sympathetic and Parasympathetic systems)? :) Either this or I have been lied to my whole undergraduate degree, haha :)

  11. Hi Ludvig, I completely resonate with all of your articles so thanks a lot!
    Quick question, I would like to try fasting but turns out I am a pretty skinny guy and focussing on gaining muscle mass (which I have had a difficult time succeeding in) thus I have to ingest many calories. fasting is not compatibile with gaining mass is it?

  12. marshall erling says

    In terms of supplements, did you entirely skip all or just some of these during your 2 day fasting periods?
    Vitamin D
    Magnesium and zinc
    High quality Omega-3 (lots of EPA & DHA)
    Olive oil (high polyphenol value)
    The above supplements are ones you have highlighted in one of your other posts. I’ve experimented with the two day fast and loved the result the second day. Thanks for all you’ve done in preparing the vast material you’ve published.
    P.S. “The Ultimate Commonplace System” is beyond fantastic. As a 48 year old reader and long-time practitioner of similar habits, I find no words to adequately praise the content and value. I want to discuss so many impressions I’ve had as a result of reading this and your early release of BOOH. I’ll be first in line to obtain your official release.

  13. Hello and Thank you for this great site and information. I may have missed it but I can’t find what qualifies as a 48 hour fast. Should you go by the last time you ate and add 48 hours to that time frame? So for me I last had a meal at 6PM last night. Do I go 48 hours from that point and eat again at 6PM tomorrow night or do I start at 6AM today when I awoke for the day and eat again at 6AM Wednesday morning? Thank you!

  14. Hey, I’m on a 40hour fast right Now and finished with some cardio, felt great. I only drank tea and water during this process, 0 calories. When you day only eat 50 cal at a time do you mean 50 cal a day for these 2 days?

  15. Alex Strick says

    I thought you might be interested to read the results of another experiment with fasting:

    Damien makes the interesting point that ketosis really only starts to kick in around 2 days after starting, suggesting that for many people the good feelings will only start at that point. Indeed, this echoes with my own experience following this 2-day protocol (albeit without the glutamine supplementation). I felt pretty horrible for most of the time, though it started to ease towards the end. I wonder whether you are perhaps better keto-adapted so it was easier for you to switch over to that fuel source?

  16. Hoy do I take my vitamins, omega 3, and calcius, magnesio, zinc while fasting?

  17. Great article. I had read a bit about fasting, and did my first voluntary fast a couple of weeks ago. I just drank water and black coffe.

    I ended it at 36 hours, but was surprised by the positive cognitive effects. I really wanted to try it again, but wasn’t sure about frequency.

    I’m up for weekly 48 hour fasts. Sunday night through to Tuesday night seems optimal.

  18. Hi Mr Sunstrom! Great article. I’m planning on implementing the 2-day fast weekly for a while in order to help me lose some weight.

    I currently take some vitamins each day and wondered what you thought about whether or not I should have them on a fasting day? These various things include – multivitamin, zinc, fish oil, magnesium and dandelion root. I also have glutamine each day but I see that you recommend that for fasting already.

    Appreciate your time!

    • I’m not Ludvig, but anecdotally I’ve tried both taking my creatine/vitamins (fish oil, multivitamin) and not taking them while doing weekly 48-hour fasts. My results have been the same. They won’t spike your insulin and there is little to no caloric value. Personally, I’ve decided to keep taking them during the fast.

  19. Now see here my good man, you hype me up and tell me this 48 fast is going to be this, and do that and release dopamine and make me more focused and its great to do every week and then you tell me you no longer do them weekly, just occasionaly. I must say, i felt a bit let down. I thought you were a life long advocate or something. Anyway, im still going to give it my best shot. Thanks for an interesting read.

    • Agree with Pete. What gives, Ludvig – why no longer regularly fasting? Any other tricks to produce similar cognitive benefits without abstaining from food? Is this about a fasting lifestyle, or getting to your ideal weight and then managing it from there?

  20. Hey Ludwig, great post! I have a question, though. When you do the 2 day fast from Sunday to Tuesday, do you hit the gym Monday AND Tuesday? Because I did it last week and I must say, even though I could go through the whole fast with no hunger whatsoever and was able to have a great gym session on Monday (this would be normal, because of my IF regimen), Tuesday was a different story. I couldn’t do my normal workout because I felt weak. I did it anyway, buy my strength and resistance were compromised. This week I´m trying it again, but without training on Monday, and breaking the fast after hitting the gym on Tuesday.

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