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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“Breaking out of Homeostasis is one of the most important books I have read in a long time. You read one or two books every few years that completely change the way you see the world and this is definitely one of them.”
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  1. Great article, and great results! I just finished a weekend (48 hr) fast, after a week of calorie reduction. I found it pretty hard! The first night I slept great even though I felt “hungry”. I ate one “Lara Bar” the second night because my stomach was bothering me so much I couldn’t fall asleep. Nonetheless I lost almost 5 lbs in the 2 days. Also felt very clear and focused some of the time even though my digestive system was complaining almost all of the time. A strong indicator that I am (was) really a bad “food addict” – even though I exercise regularly (mostly endurance training, with some weights). I am looking forward to more of these 2 day fasts to re-regulate my system to see food as fuel and overcome unconscious habits, and to make it easy to maintain optimal weight and get “ripped” as you say. Thanks for the info.

  2. Jordan M Williams says

    Dude, I am 7 days post my first 48 hour fast and I feel like a million bucks. Thank you for this article, this will be something I use very regularly.

  3. You wrote the article completely based on the possible fat burning properties of a fast, not hormonal changes in testesterone and hgh in men. Glutamine is not needed as a suplement unless you’re a frickin’ marathon runner. It’s a non-esential amino acid meaning your body produces it’s own (and it does it quite well).

  4. Thank you.

  5. kristiannie says

    I have done several short fasts in my long life and one extended (60 days) one. My fasts have always been with home made fresh pressed organic juices — mostly green — and my understanding has always been that if you strain all of the solids out of your juice your digestive system will NOT kick in and the nutrients from the juice are just directly absorbed. I have just recently begun 48 hour fasts once a week, using some bone broth and juice but mostly water. It works for me and feels more appropriate for my 68 year old (happy and healthy!) body.

    • That’s different.
      I have little experience with doing juice fasts (never gone over 1 day of doing it), so I wouldn’t know about that.

    • I’ve done a 7 days juice fast and did lose some weight (years ago).

      You won’t be in ketosis though, because of the sugar in the juice, so it’s not the same fat burning effect. Maybe one glass would be ok, but that would defeat the purpose I think. Get nutrients through food on the other days, without overdosing on sugar.

  6. 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

  7. 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!

  8. 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 …:)

  9. 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 :-)

  10. 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.

  11. 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.

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

  13. 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?

  14. 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?

  15. 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 :)

  16. 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?

  17. 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.

  18. 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!

  19. 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?

  20. 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?

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

  22. 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.

  23. 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.

  24. 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?

  25. 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.

  26. I also do a weekly 40ish hour fast (typically after dinner Sunday -> Tuesday after workout) and follow 16:8 most other days. I find myself referencing the mental and physical benefits of a weekly 40-hour fast quite a bit in my blog posts because it confers so many of them. For instance, it was Halloween here in America several days ago and I gorged on candy. Yesterday was my fast day, and bam, my body is completely reset and I’m only craving healthy food again. I love it. Keep up the good work, I’ve been enjoying your content for a while now!

  27. I guess at the day of the day it’s basic Math. 2 day fast you have saved about 4,000+ calories from your weekly amount. If you were fairly careful the other days you’d always be losing fat.

    I can see how after a couple of months the danger is going to be cutting too much.

    So do it until you have your fat %…then drop to once every couple of months to maintain. Obviously, you still can’t pig out.

  28. Hey Ludvig, great information!
    What are you thoughts about applying this as an ectomorph / skinny? I plan to implement it in the future but I’m a bit worried because being a natural skinny person with a fast metabolism makes harder to eat a lot in one sitting.

    Best regards.

  29. I wanted to thank you for your information and I want to try to add something. There is a study regarding a miracle cellular process called Autophagy that most BCAA can kick you out of that process. This process is huge for health and looks to be vital for longevity anti cancer in particular. Eight amino acids, Leu, Tyr, Phe, Gln, Pro, His, Trp, and Met, suppress autophagy but especially Leucine. ( Glutamine also inhibits as well ( There probably is a slight loss of muscle mass but it appears that 6 steps forward and one step back is a small price to pay. I’m now just starting a 48 hour fast from Saturday night to Monday evening. I’m working out full body 6 days a week with no reps to failure allowed, one 20 reps and one 3 or 4 reps, and lots of protein. We’ll see how it goes.

  30. have you ever experinced bad breathe when fasting, and if so – have you a trick to make it go away ?

    bad breathe comes from not having eaten anything you know :)

    • And how do you calculate how much fat is burned in a fast (ketosis) for 24 hours ? :)

    • I’m not Ludvig, but I started following IF after reading about it here a long time ago, and have used his 2-day fast method a bunch of times.

      I do not experience bad breath (any worse than normal) and as for calculating fat I have no idea…but I have lost a bunch of weight and if I continue I should be semi-ripped in a few months. I do IF every day and 2 day fasts every second week.

  31. I was 43 hours through a 2-day fast today, when something interesting happened. I was feeding my dog, who after taking just one bite of dog food, stopped eating. She came over to me, (sitting down next to her) and sniffed my breath a couple of times. Then she backed up a couple of feet away from the food, looking from me, to her bowl, and back.

    This is curious.

    ((Normally, as she only eats 2 cups of dog food per day during a single meal, she will DEVOUR her food as soon as it is given to her. She NEVER leaves anything left.))

    It is eight hours later and she still hasn’t touched the rest of her food. I wonder if anybody has an opinion on this? Do you think she could have smelled the ketones from my breath, and as a group evolutionary trait she was then willing to give up the rest of her food? I am curious to see what others might think.



  32. I’m 41 hours and counting into my weekly sesquiday fast. It’s great.

    I studied collaboratively this morning with full focus, worked out hard this afternoon, and am going to follow your suggestion and do some more reading and research.

  33. MAN this is some great stuff! I’m trying this out, right now I’ve been fasting for the last 24 hours, going for another day. I can feel the focus running through my brain.

  34. Thanks for this article and your description of 5:2 with just two days of calorie restriction as being for “weaklings”. I LOLd, and agreed.

    I am not going to do your two day fasts (not scheduled, anyway, unless I feel like going over). I am instead going to fast for a sesquiday per week.

    • Make that I am going to do two-and-a-half-day fasts (scheduled, anyway, unless I feel like going over). I am going to fast for a sesquidupleday per week.

      • Did you do it yet?

      • No, I did not!

        That is a good question, and was on my mind. While I did a few day and a half to almost two days fasts, never did do the two and a half day fast I planned.

        So, I’m changing it to, as a regular thing, eating within an eight-hour window as nutritious foods as viable for me based on circumstances and drive. Was going to do a tighter time-restricted feeding window, but I figured if I’m aiming for the most nutrient-dense foods relative to Calories viable, I could use the extra couple hours to make sure I’m not quasi-forced to eat junk foods to get enough Calories in.

        Thanks for posting great articles on other types if intermittent fasting also, and for asking me this question, which psychologically forced me to be accountable for my publicly stated intention.

  35. Am I allowed to chew gum?????

  36. How often should practice 48 hours fast?

  37. Could this also work for a woman?

  38. I read this article some weeks ago and decided I would try it out — and lo and behold you were actually right, I did get ‘*high* after about 15 hours of not eating! Awesome! ;)

    I tried it again yesterday but it was too hard and I gave in and ate before I felt anything :(

  39. For a few years me and some friends would to the occasional week-long fast. Not really from a healthy point of view though, it was more to test our limits, and the fast would be broken with lots of alcohol and bruises. Stupidity, but somewhat interesting. Last one I did was for 8 days straight, while studying, definitely had more focus and got lots of work done but was irritable and slow most of the time. 2-day fast sounds great though, how often would you do it? Every week? Great website, and cool to be inspired by another Lundabo!

    • Hey Johan,
      One week? I’ve tried that a few weeks ago — I’m not doing it again anytime soon. Didn’t break it with alcohol though.

      How often? for a few months I did it every from Sunday evening to Tuesday afternoon. It would be a 44 hour fast broken with a gym session and a big meal. Now I do it every once in a while. I did it 3 days ago last time.

      Glad you like the site.

      • Wow man. I had a chip on my shoulder because I’d lost 25 kg a few years ago from superlow calorie (200 cals a day) intermittent fasting. Ive always been almost arrogant about my ability about it. Reading this is such a humbling experience. I’m a super-competitive guy, I’m gonna beat you at your feats of will power! haha

        I’m increasingly becoming obsessed with the contents and tips of this blog. If you’re looking to create “A movement of like-minded individuals.” as you say. I’m certainly a part of it young man :)

        It’s important to be constantly challenging your limits, to be well read, to strive for focus and personal perfection as a way of life, and its very thrilling to read about someone who shares these ideas

      • Glad to hear it Shaun!
        And be sure to let me know when you beat my feats of willpower. Thanks for the email as well.

  40. Nice post ludvig.

    Not only is a 2 day fast great for all the above reasons its also great way to prevent getting sick and allowing your body time to recuperate.

    • Hey Code,

      That is my experience too, after having experimented with it about 5 times when I’ve had colds and recovered quickly.

      Not sure if it’s a good idea for someone who’s never even done IF (16h+) before though. Perhaps it would just add stress to the body, and mess up the immune system further…

  41. I’m starting today with my first two day fast experiment. Some new research about it, fasting for two days can regenerate the inmune system:

    • I’m not surprised, Carlos.

      There’s a ton of research coming up about fasting lately. At this point, I’m not very interested in it though, because I know that it working well for me.

      Another interesting thing about fasting — that I recently learned — is that it can be used to reset your circadian rhythm. This is especially useful for when you want to wake up at a new time in the day. Just don’t eat anything for 20+ hours, then when you have your first meal, you’ll trick your body that you’re starting the day.

  42. Nice. Have you ever tried an all water fast? Did you notice that when you took the 3-5 hour glutamine breaks, it make you foggy-headed/food obsessed again?

    • Hey Hannah!

      “Have you ever tried an all water fast? ”

      –I have. And I don’t like its effects as much.

      ” Did you notice that when you took the 3-5 hour glutamine breaks, it make you foggy-headed/food obsessed again?”

      –Nope, and that’s why I take it. But I suppose that can happen if you take it too frequently or in a larger dose than 5g at once.

      I much prefer the L-glutamine + caffeine combination to a water fast. That way I am never hungry, and — as an athletic person — I don’t need to be the least afraid of my muscles being ‘eaten’ by the fast even if I am already pretty sore.

  43. What do you think about alternate day fasting? Eating one day and not eating the other.

    • Hey Vorth,

      I couldn’t tell you… I’ve never done it for more than 4 days (1 day eat, 1 day fast, 1 day eat, 1 day fast). But it was fine for that time.

      If you decide to experiment with it for 30+ days, I’d appreciate it if you shared your experience!

  44. Wow great read, I have only been been looking into fasting the last few days after seeing a post on FB from a mate who had lost heaps of wait. It was under a post about the UK Doctor/reporter who did the documentary about fasting, he just wrote “this doco changed my life”. After watching it I still had a lot of questions until I found this site. Originally I wasn’t sure but now know I can do 2 straight days once a week. I’m a fat cabbie & have over the last 15 weeks lost 14 KG but it has been getting hard. This I hope will suit my cab driving & maybe sneek a hamburger in once a week :-) I am currently 24 hours into my 1st fast & feeling good & planning to have a sleep (I work nights) & go through until 8pm which will be 41 hours & then plan on doing the 16/8 until I repeat it again next week. one problem I have is I hate tea & coffee so it looks like just water for me or maybe a little diet soup ?? Thanks again & will keep u up to date with how I’m going.
    Cheers Mark

    • @Mark,
      Noticed you said you can’t do tea and coffee, but have you ever tried herbal teas? There are hundreds of different kinds ranging from fruity to minty to earthy and everything in between. If you can get Celestial Seasonings teas I highly recommend them.
      When I am fasting I tend to get more hunger pangs if I drink something that reminds me of a food, so YMMV.

    • Hey Mark,
      Thanks for the comment.

      “over the last 15 weeks lost 14 KG”

      — Great job. Keep it up. It’s hardest at first (first 30 days or so) before your body adapts to it. Then you won’t even think about it. You may want to try the water + 5g of glutamine. I always do that during 48h+ fasts.

      And I always have some glutamine in the morning ASAP upon waking up (I never have breakfast).

  45. Really nice article Ludvig! I’ve always wondered what really happens to your body when you fast and this answered all of my questions. I started fasting 15 hours ago for the first time and I’m planning on going for 30 hours. I’m wondering if the increased alertness also has something to do with cortisol levels in addition to switching from the rest-and-digest system. There once was a study done on prisoners in which one group of prisoners were constantly exposed to stress (for example a flooded living space) and another group not exposed to stress. When you’re stressed, your body releases this hormone called cortisol which if I remember correctly it provides the body with increased energy taken from the muscles and fat of the body. This goes on until the body runs out of stored muscle and fat. Maybe the body produces cortisol during a fast and in turn leads to ketosis? Just a random thought…

    • Hey Rui,
      Thanks. How did it go with your fast?

      I am familiar with cortisol. Yes I think the body produces some amount of cortisol during a fast, but I don’t think it’s the main reason why the body gets into ketosis. Interesting thought though, I will read more on this soon.

  46. Interesting read. I have definitely done intermittent fasting enough to see some of those benefits (paleo dieter), but now I’m going to have to amp it up! What you describe seems like a more potent form of what it feels like to be on a ketogenic diet, which I have done 2-3 times for periods of a few weeks to a few months. This is difficult/uneconomical to maintain for longer periods of time without significant dairy consumption (or serious investment in quality animal and plant fats), so fasting sounds like a better alternative. If you ignore the popular knowledge, it just makes sense that our ancestors would have frequently gone long periods of time without eating (for lack of finding food).

    BTW, I just downloaded the copy of your book and am very excited to see what you have to say.

    • I think you’ll find it satisfactory, Tom.

      “If you ignore the popular knowledge, it just makes sense that our ancestors would have frequently gone long periods of time without eating (for lack of finding food).”

      —> I absolutely agree with this. I almost find it hard to believe that the majority of people in the Western world eat a minimum of 3 meals per day (what might be average be? 5?).

      I can’t understand how they get anything done. If I eat all the time I get lazy and complacent.

      I’m glad to hear you got the book. Feel free to send me an email if you have any questions. Or to leave a review/comment on the book page of the site should you feel like it.

      • I’m planning on doing a 24hr fast starting tonight to get my body used to it.

        I also don’t see how anyone does 3 square in a healthy way (preparing each meal themself). IFing and eating one big meal a day is enough work for me. I loved it when I could work on my capstone engineering project for as long as needed without having to break for food. Now that I’m working full-time I can skip lunch (flex time) and go home an hour early without any negative side effects.

  47. Kanye Smith says

    Hey Ludvig Ive been trying this out for the past couple of weeks and I gotta say it feels a lot like how you describe it: being focused and calm.
    Ive lost a bit of weight too. If you got more of these tricks lined up I’d like to hear them.

  48. Hey Guys I been thinking of trying the longer fast’s like a 48 hr one… I been doing IF(16/8) for about almost year and half and I seem to plateau on my gains..I’m stuck at about 9-10% body fat. I’m 5.7 weight about 155-160 . Do you think it will break that plateau?



  49. A few days ago I just finished a 72-hours fast.

    While it’s definitely liberating to not to have to think about food for a couple of days, I found that prolonged fasting takes a toll on your training performance.

    I was able to squat four reps less with the same weight (I tested myself a couple of days before starting the fast, fully loaded with them carbz) and I underperformed on a bunch of other exercises.

    Next time, I’ll try to stick to a 2-day fast. From my experience, this seems to be the sweet spot.

    • I see.

      I’ve felt the same thing the few times I’ve done 48+ hour fasts. I think it has to do mostly with the fact that my body isn’t used to it since I don’t do it particularly often.

      However, I don’t see a reason for going longer than 48 hours. In that case it would be to do it as a willpower exercise or to try to be like one of those buddhist monks who fast for weeks on end to get in touch with God etc.

  50. Michal Stawicki says

    Evryone is different. Extended periods of fasting make me feel irked, sleepy, tired and weak.
    Apart from rapid weight loss I don’t gain any other blessings. Well, willpower training maybe, but I don’t need it very much. I think I could subdue the whole mules population with my stubborness ;)
    Having said that, I still fast regularly 33-36 hours every week.

    • That’s true. But it also has A LOT to do with whether your body is trained to run on ketosis or not. Personally I eat very little carbs, mostly from broccoli and spinach and some quinoa/brown rice.

      This makes it easier for me to fast.

      I would not recommend someone who has never even done IF (16-24 hour fasts) to go longer. It can definitely lead to you feeling weak and tired. It’s usually not dangerous, it’s just your hormones throwing tantrums due to being yanked out of homeostasis.

  51. Adrian Elizondo says

    Recently in this holidays I am having huge meals and then fast for 40-48h, still leaning out, but I am worried about some health issues due to doing it more than once a week.

    -Do you think i Should worried? or just continue and Stop doing it after Holiday season, maybe two or three times more are Left jaja

    Great Blog, by the way. Found it by BoldandDetermined

    -Elizondo Adrian

    • Adrian,

      Thanks for the kind words.

      I don’t think you have anything to worry about unless you suffer from some strange disease I don’t know of.

      No doubt you’ll be very lean in a few months if you continue the fasting.

  52. Man, I’m so glad I found this website :)

    The best writing I ever done was always on a longer fast + some coffee. It never seizes to amaze me how well my brain works on a longer fast.

    Btw, what’s your longest fast? Mine was 48 hours :)

    • I’m glad you like it Dejan!

      I’m not sure if my best writing has been done while fasting (possibly), but my best reading definitely has been, and is. I can read non-stop for 10+ hours when I’m pulling one of these fasts. I become an information-gathering machine.

      The longest fast I’ve done was actually just a week ago. It was just under 90 hours I think.

      • Yeah, the concentration level is something else … I need to start doing longer fasts again, as soon as I finish my “bulking” experiment :)

        Have you experienced any lightheadedness or any other weird feeling/side effect, during the 90-hour fast?


  53. Intermittent fasting is one of those things that have always sounded too good to be true to me. Especially if you add benefits like increased focus and better memory.. but because there’s no “buy my 300$ guide on the 2 day fast!” button, and the info is all laid out, and of course because it’s coming from you, it’s pretty hard to dismiss. Who knows, maybe it’s a leftover function from being cavemen and it has a survival property. Like enabling better performance to land a kill so you get the food you need to survive another week. Definitely going to try this, will have to see what it’s like for myself!

    • I know what you mean, it’s easy for someone who isn’t doing it to categorize it as some fad or a silly diet. But it’s not a diet, it’s a lifestyle.

      I agree with what you say about the cavemen leftover function. It makes a lot of sense from an evolutionary standpoint.

  54. How often would you do this

    • Last year I did it about once a week (in addition to my 16/8 IF).

      This year I haven’t done it that often. Maybe once every three weeks.

      • Is there anything wrong with more frequent, extended periods of fasting (such as this)? I know you mention somewhere that you eased back on the 48 hour fasts due to concerns about losing too much weight. Other than this concern, would it be possible to fast like this more often? I find the improvement in mental state fantastic–and I want to fast like this more often (I normally eat 1-2 meals a day but the results of this are negligible in comparison for me mentally). Is there any reason this might be a bad idea?
        Also, interesting point about needing less sleep during a fast. I wonder how fasting influences REM % and quality of sleep. I know Tesla was a faster as well as a polyphasic sleeper -perhaps the latter may have allowed for the shorter time spent in bed.

      • Try and you will see :)

        The worst thing that can happen is that you get extra hungry.

        Regarding Tesla: I have thought the same thing.

        I have done polyphasic sleeping and fasting too. But I couldn’t combine it with going to the gym.

  55. Correct me if I’m wrong, but why do you want to get people to fast?

    • Because it made a big difference in my life when I started it. I’m not telling people to immediately start to do it as “extremely” as I do it.

      It’s a very empowering feeling to KNOW that you don’t have to eat much. I’m currently 74 hours into a fast and I’m going for 100 hours (new record). I feel superb.

      (Gotta beat Trevor’s fast! Haha)

  56. Hey Ludvig I just read this post and the One about getting ripped. Very cool shit.

    Im gonna give this fasting thing a try over the weekend. Ill let you know how it goes.

    Maybe Ill even beat Trevors fast ;) but i wouldnt count on it :p

  57. This is very useful information. I’ve been considering adopting a plan like this for some time. I have a friend who’s currently utilising the calorie-restricted method and swears by it. But I’m liking the sound of the cognitive benefits you describe here. It’s an unexpected bonus. A question: Do you ever have instances of the high lasting beyond the fasting period? Or does it taper off fairly immediately.

    • Calorie restriction works for sure, but it’s just so much more work.

      Fasting is a lifestyle. It’s very easy once you get over the inital 2-4 weeks and your hormones adjust to the new eating pattern.

      Yes, it tapers off rather quickly when I eat. Not sure how quickly, but probably within 30 minutes.

  58. I love ideas like this. I have been on various Keto diets, 5:2 diets, low calories diets, bulking diets etc etc and had mild success with all of them. The longest I have been without eating anything is, I think, 24 hours.

    I will try this in a week or so as a means to increase my insulin sensitivity.

    Great post and ideas!

    • I see.

      I’m sure it will increase your insulin sensitivity if you do it consistently, but I doubt it will make any drastic change if you just try it once or twice.

      Thanks for you comment1

      • I agree, nothing works if you do it once. Real change takes discipline and consistency.

        I meant that I will start doing it, rather than doing only once. I will try it, see how it feels and then maybe do it once a week as part of my current diet.

        Yet, even if you do this once every so often, I believe it can have positive effects over a long period of time.

      • Ah, alright.

        Let me know how it works out Jamie!

  59. This is really interesting man. Up until I read your other post on what you eat on a regular basis I didn’t really know anything about fasting. But clearly it’s working at a really high level for you.

    I also love how much time it would save in your daily life.

    I wonder if the fasting you do works so well because of the bodies natural conditioning over hundreds of thousands of years. I doubt the cavemen ate three square meals a day. Fascinating shit.

    • Kevin,

      Yeah you should try it. Me and Trevor already are ;)
      Let me know how it goes. For some reason I am very keen on converting people to IF, probably because how much it has benefited me.

      Today I’ve only eaten one meal (not counting some glutamine, raw cocoa, and creatine that I had pre-workout).

      Thanks for the comment!

  60. Hey Ludvig, I just finished up my workout so I’m reporting back how it went.

    I’m not sure of the exact hour I ate my last meal (I hadn’t actually intended to fast for more than one day) but it was shortly after I got home from work last Thursday, which was noonish (I work baker’s hours . . . extremely early).

    I ate shortly after I got home, so maybe 1-2pm. I finished my workout around 10:30am this morning, so roughly 92-93 hours into my fast (if my math is right). I kept it quick and light — just some pullups and shoulder/arm work. Here’s how it went . . .

    I noticed zero decline in strength or endurance. I did notice that it took me a bit longer to recover during my first few sets, but by the end of the workout I was taking even shorter rests than usual. I didn’t get much of a pump, even less than when I’ve been going super low carb for a few weeks, but it didn’t make much of a difference. I did start to get some tightness in my sides towards the end of the workout. Not quite cramps, but unpleasant nonetheless. Maybe an electrolyte issue? It’s not the first time that’s happened to me so I’m reluctant to blame it on the fasting.

    So all in all, I had a solid workout. I’m sure I could have done more and pressed harder, but since this was my first time working out so late into a fast, I played it safe. I don’t think I’d ever want to go super heavy after a long fast since I tend to get a bit light-headed at times when I’ve been fasting 48+ hours.

    After my workout I crashed pretty hard. I was sleepy and just lied on the couch for a while. But I’ve crashed harder after workouts that were not fasted, so no biggie.

    So I’ll be cooking up my meal soon and eating roughly 96 hours after my last meal. A full 4 day fast with workout. This shit CAN be done.

    Thanks for the inspiration Ludvig! I just learned something new about myself after all this. Next up, the 5 dayer. Should be fun . . .


    • “…roughly 92-93 hours into my fast”

      —> That’s some badass shit right there, very impressive!

      “So I’ll be cooking up my meal soon and eating roughly 96 hours after my last meal. A full 4 day fast with workout. This shit CAN be done.”

      —-> I’ve never worked out past 50 hours of fasting. This makes me want to try it as well!

      I’m glad you stepped up and did this Trevor.

  61. Alexander Skafte says

    Been doing a ~17 hour fast every day (skipping breakfast) for two to three weeks now. It’s not that hard really. Been thinking about doing the 24 or 48 hour fast for some days now. Before you do the fast, do you eat A LOT? Like, stuffing up on as much food as possible?

    • Awesome man, that’s what I usually do as well.

      No, I don’t deliberately eat any more food than I would usually.

      PS: For anyone else reading this I recommend checking out Trevor’s link below on 70 hours of fasting.

  62. Trevor, what an inspiring and unusual story! It makes me want to try this fasting thing out!

    I just hope I don’t end up baking bread as I am gluten-intolerant.


    Do you notice much of a difference from day 1-3 after getting over the initial hunger plateau?

    • Hi Kara, I’ve never noticed much of a difference. The first day is usually the hardest. But after you’ve been fasting for awhile, even the first day becomes a breeze — I rarely get hungry anymore.

      I’m currently 80+ hours in to my latest fast. I was gonna end it yesterday, but Ludvig’s post inspired me to give it one more day. I’m gonna end my fast with a workout and a huge-ass meal. Then I’ll report back here with how that end-of-fast workout went. As of right now, I’m feeling pretty damn good and energetic. We’ll see what happens.

      You should definitely give fasting a try Kara. A simple 24 hour fast is a good way to start. It might be difficult at first, but it really doesn’t take long for your body to adjust. By the 3rd 24 hour fast it’ll be nothing. And you’ll come to the realization that much of your hunger is simply routine behavior. Fasting gives you control over that hunger.

      I believe most people would benefit from fasting. But I’ll add this warning: fasting is NOT for people with a history of eating disorder. For the rest of us though, it can be a very healthful practice so long as we don’t get carried away with it.

      And don’t sweat it Kara, fasting won’t turn you into a baker. No worries.


      • Solid advice. I agree 100 %.

        People are overly controlled by their hormonal hunger. It’s pathetic to watch when doing group work with people and they have to eat a snack every second hour just to function normally…

  63. I’ve been fasting for years Ludvig. You’re absolutely right . . . it’s a healthy practice for both mind and body. I started with a 24 hour fast. Moved to 36. Then 48. And lately 72 hours for a full 3 day fast.

    It becomes very easy over time.

    I only drink coffee (black), and sometimes a glass of wine, when I fast. No food, no supps. It feels great!


    • I couldn’t agree more.

      Once you start fasting there is no going back, it’s just superior in any way possible once the initial phase of hormonal discomfort is passed.

      I’ve done a few 3 day fasts, but I haven’t had the energy to break them by working out. Do you ever do that Trevor?

      • I haven’t yet. Though low energy has never been a problem at the end of one of my fasts. I’ve just never seemed to time up the end of the fast with a workout.

        Makes me wanna give it a try. But then I’d have to wait until my workout tomorrow. That makes for a roughly 84 hour fast.

        Hmmm . . . perhaps we’ll see.

        I’ve certainly never had a problem working out after 24-36 hours fasting. Some of my best workouts came after 36 hours with no food. Never had a decline in strength or energy.

        And the huge meal afterwards is just so damn satisfying.

        As some added insight, my very first 3 day fast (74 hours, actually) was a life changing event. I knew I was doing something meaningful and important, but I didn’t realize at the time just how profound an effect it would have on my life.

        Especially considering it simply started as a result of a bout of indigestion . . .

        I don’t normally include links in comments, but if you’re interested, I wrote about that first 3 day fast on my blog. As background, I was a bread baker for over a decade before I quit baking out of disillusionment and bitterness.

        At the time of my fast I was working at a computer company. During my fast (more accurately as a result of my fast) I came up with a post about lessons in passion I learned as a baker. It was my most popular post at the time.

        And it got me thinking . . .

        About bread. About baking.

        And I couldn’t get it out of my head. That post brought back the passion. It brought back the love. And I came to a decision. That post (and that fast) set me on course to return to what I love — bread baking.

        Well, that was a long story. Anyway, here’s the link to that original post about my first 3 day fast. I hope you enjoy . . .l


      • I see. Let me know how it goes when you try it out!

        Interesting that you found your passion through a fasting-induced moment of clarity!

        That’s a cool post man.

  64. Interesting stuff Ludvig. But what about working out, how is your 2 day fasting reconciled with a typical week of gym/workout sessions?

    It would be cool to know.

    • Mike,
      GREAT question. I will actually add this to the post.

      The short answer is that I often break my fast with coffee followed by a workout, and then a huge ass meal. I will usually keep the workout to around an hour because after that point I’m drained, which isn’t weird because when you work out in a fasted state you’re using your body’s “reserve fuel tank” of glucose, and it runs out.

  65. Lol, I like how you bash the 5:2 diet.

    It really annoys me when “fads” like this pop up and everyone acts as if it was new under the sun.

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