The three-day water fast

Dr Tallis Barker, water fasting coach

Of all fasts, the 3 day water fast is in many ways the most important. Three days is the period your body needs to unlock your healing metabolism and begin reaping the benefits. These three days are also the stepping stone required to move on to even longer fasts (such as the 7-10 day water fast and more prolonged fasts), in which the deepest healing can occur. The more you practise the three-day fast, the easier you’ll find water fasting of any length.

I’ll be honest with you, though. In the beginning, the 3 day water fast is also often the hardest.

Because of this, it’s important to do everything you can do to maximise your chances of a smooth experience. This can include following a well laid-out plan, such as that found in: The Complete 3-Day Water Fasting Program® and Living on Water®. For those who need more personal contact, I also offer online consultations and coaching.

Whether you choose support or to go it alone, it’s definitely better not to try and bite off more than you can chew 🙂 with a 3-day fast until you feel comfortable with one-day (36-hour) water fasts. This is because a 3-day fast really is a quantum leap ahead in terms of what it demands from your body.

What are the challenges and benefits of a 3-day water fast?

Before you gain greater experience, most of the challenges of the three-day water fast are physical, as your body learns how to enter the state of ketosis. Ketosis is the process of burning fat directly from adipose (fat) tissue, which is achieved through the production of so-called ‘ketone bodies’ in order to metabolise the fat. Unless you happen to be following an extremely low-carb diet, this is entirely different from how your body normally extracts the energy needed to power each cell. As a result, the vast majority of people never experience ketosis in everyday life, and rely instead on metabolising carbohydrates until the day they die. This is a real shame. We have two eyes, and we use them both. We have two arms and two legs, and we use each of them. We also have two metabolisms: our everyday carbohydrate-based metabolism, as well as ketosis. They each serve their own function and offer their own benefits.

There are two huge benefits of getting into ketosis while you fast. First, because you’re burning fat and not eating, your body frees up a lot of extra energy for healing. (It’s estimated that digestion accounts for about 30% of your total daily energy needs.) Second, because you’re burning fat cells, you gain the potential to burn up and cleanse toxins which have been locked there for years and years. This is a different mechanism from being on a low-carb diet and burning fat in everyday life, because in this case essentially the same fat cells are used for energy, over and over. In contrast, deeper levels of fat remain untouched: with their toxins accumulating within.

What happens on a 3-day water fast, day by day?

Day 1:
Of course, the first day feels the same as on a one-day fast (described in greater detail here), as you slowly exhaust your reserves of carbohydrates, which are stored as glycogen mostly in the liver, as well as in the tissue surrounding your muscles. Psychologically, though, you should feel much more comfortable – given that you already have experience in surviving one day without food. Surviving three days without food is simply an extension of this, and so hopefully you’ll be freer to concentrate on the physical changes taking place inside you. You may indeed find yourself facing your ego over these three days, but it’s more likely to take the form of facing your addictions to food rather than facing your ego’s existential fear for survival.

Day 2:
By the beginning of the second day your glycogen reserves will have run out. At this point, how you feel depends on how much experience you have in fasting. Nowadays when I fast, I feel great because my body has made the switch to ketosis in tandem with my glycogen stores running out. In other words, I don’t suffer any ‘power loss’. In fact, I usually benefit from even fuller energy towards the end of the first day because I’m powered by two sources: my usual carbohydrate-based metabolism (before the glycogen stores completely run down), as well as by ketosis – which starts to kick in a couple of hours after I miss my first meal. It’s a great feeling, and, in time, you can look forward to it too!

However, if your body isn’t adapted to ketosis, things will probably be rather different… Your glycogen fuel tanks will hit empty, and your body will have to (continued below)

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search for an alternative power source – and quickly too! The burning of fat through ketosis is highly efficient, but the problem is that your body hasn’t yet learned how to easily access this metabolism, because the chemical reactions involved are so different from what you’re normally used to. Instead, the next closest source of energy is through burning protein – and this comes from metabolising your own muscle tissue. Don’t worry, you’re not going to lose any significant muscle mass. We’re talking about only a few hundred grams until your body has started to perfect ketosis by the end of the third day. From this point on, any further loss of muscle mass is minimal.

In the meantime, though, you’ll probably feel extremely low on energy. Your muscles may ache, especially in your legs and back, as your body sacrifices muscle tissue. Headaches are also common, both from low blood sugar and lack of energy, as well as from the beginnings of detoxification. Dull aches around the kidneys are also common, as your kidneys start to work overtime, flushing out the first toxins from your fat cells as well as the extra acids caused by metabolising protein. If so, make sure you’re drinking enough: at least a quart/litre or two per day. There is no fixed minimal limit to drink. This depends mostly on a person’s level of toxicity. The higher the toxicity, the more you’ll have to drink. Many people drink 3-4 quarts/litres a day.

I don’t want to lie to you. Personally, I feel that too many books and websites on fasting paint a rosy-coloured picture of how you’ll feel. Telling the full truth might turn off potential converts to water fasting… Yes, perhaps you’ll feel like a million bucks. But for the first couple of three-day water fasts it’s more likely that you’ll feel pretty awful, not entirely dissimilar to how you experience the flu: with aches and pains, and a general lack of energy. But don’t worry. And don’t give up at this point!!! You’ll survive. Just hang in there. All these symptoms will pass.

Day 3:
The third day is more or less a continuation of the second, both in terms of the physiological processes taking place, as well as how you feel. Many people feel at their lowest at the end of the second or at the beginning of the third day. Generally, though, things start to improve after this, as the switch to ketosis is completed.

If the toughest part of a fast is getting through the first three days, then isn’t it worth diving straight into a longer fast and reaping the benefits of what you’ve suffered through? Maybe. If you have the energy to do so, then by all means! Most likely, though, your first few three-day fasts will leave you feeling drained both physically and emotionally. There’s no need to do any more at this point. Three days is enough. Mission accomplished. You’ve successfully awoken your body’s healing metabolism, which you’ll be able to rely on increasingly in the future. You’ve also already experienced a significant degree of detox. Instead, take on a longer, more cleansing fast once your body has more fully acclimatised to three-day fasts.


At the end of the third day, enjoy a glass of freshly squeezed orange juice and pat yourself on the back. Unlike longer fasts, there’s no need for a long transition back to eating. Nor is there any need for a long transition before the fast itself. However, do keep the first few meals light: mostly just fruits and/or vegetables (just as the last few meals before the fast should also be light). Don’t eat too much! If your ego is telling you to gorge yourself, avoid the temptation and try to honestly follow your appetite. Your stomach will have shrunk, your digestive system will have slowed down considerably, so you need a little time to get things up and running again. If you do follow your appetite, you’ll find you’re eating normally again in a couple of days.


— The deepest detox (click here)
— Overcoming addictions (click here)
– Enjoy the gift of food (click here)

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  1. C says

    Thanks for a great article. I was wondering if you can do a 72hr fast, eat in a short window, and go into a 24 or 48hr fast, eat in a short window and then back into a 72hr fast… or is it really only once a week that is ok? Many thanks. C

    • Tallis Barker, D.Phil. says

      Hi C,
      Thanks for writing. Anything is possible, but (depending on what you mean by a ‘short window’) you don’t want to get into a situation which becomes a jumble of fasting and eating. This confuses the body. For both cleansing and healing, it’s better to focus on longer periods of fasting as well as longer periods of eating.
      All the best,

  2. Adrian says

    How often might one do a three-day water fast? Is one every two months too frequent?
    Thanks for all the useful information.

    • Tallis Barker, D.Phil. says

      Hi Adrian,
      Thanks for writing. Essentially, there’s no upper limit to how frequently you can do a three-day water fast, so long as you’re taking in good nutrition in between. I once had a client suffering from stage four cancer who, for therapeutic purposes, fasted for three days every week (with a specific anti-cancer diet on the other four days). The doctors had given her only a few weeks to live, but instead she continued happily on this protocol for over 18 months before we finally lost contact.
      Whether you would actually want to fast this frequently is another matter altogether. But the point is that the limitation here is more psychological than physical.
      All the best,

      • Adrian says

        Super, thanks Tallis, for this thoughtful reply.
        Really appreciate your work here,

  3. S says

    Im doing a water fast because i had a sexual injury last year that also gotten another infection because of the docters topical trash. I got so depressed by seeing my penis change color and not being able to have sex or not feel pain in my penis. I’m on two days now of the fast. How long do you think i need to recover my penis. If there’s even a possibility recovering it like this… I feel helpless and water fasting is what caught my eye after all this. Thanks in advance!

    • Tallis Barker, D.Phil. says

      Hi S,
      Thanks for writing. It’s very hard to say anything specific here without knowing more about the cause of the injury as well as the cause of the discoloration and lack of sensation. It does sound as though you’d need to do at least a 7 day fast, given that this tends to be the point at which the first issues deeper start to be addressed. This is just a starting point, though. How long it would take to reach a full healing is going to depend on the cause and severity of the issue.
      Hope this helps,

  4. Steve says

    I’m on the tail-end of a three-day water fast (with a 24-hour dry fast in the middle). In one of your articles about dry fasting, you mentioned sustained tachycardia as a sign to break the fast.

    Within the last day, I’ve noticed the opposite: bradycardia. My resting heart rate (as measured by a pulse oximeter) has been in the 50s much of the time, even dipping to 49 a time or two. I’m not really athletic (though I do work a somewhat demanding warehouse job) and I’m rather skinny at 6’2″/150lb (1m88cm/68kg). I’m just wondering if this is a potential side effect of fasting or if I should be concerned.

    • Tallis Barker, D.Phil. says

      Hi Steve,
      Thanks for sharing. Yes, heart rate can and often does become a little lower while fasting. So long as you have a healthy sinus rhythm, it’s usually nothing to worry about (especially if it’s ‘only’ in the 50s). In fact, a lower heart rate during a fast is usually representative of lower levels of stress – so actually it’s probably good for you!
      All the best,

  5. Michelle says

    This was a fantastic article!! I wasn’t planning on doing a three-day fast but I’m on my third day right now because I got really sick with a digestive issue and lost my appetite anyway for about 24 hours. I decided to just keep going and give my digestive system a real break. I completed a three-day fast a few months ago and it was INCREDIBLY hard. I wanted to go 84 hours but ended up getting up in the middle of the night and stumbling down to the kitchen to eat a few hours earlier. I felt just absolutely rotten like I had the flu on day 2 and 3. This time though, since recovering from feeling sick, it is much much easier. Before I tried the 3-day fast, I did a 1-day fast (about 36 hours) a few times. Each of those were extremely difficult too, like I was so weak I could barely tolerate it.

    I’m pretty excited at how good I feel at the moment. Food seems really appealing and I’m looking forward to resuming it tomorrow, but I don’t feel so weak like I did last time and just feel like I can function okay like this. I am just glad to see that my body has been able to adapt to these. I’m looking forward to seeing how they can help me periodically moving forward.

    • Tallis Barker, D.Phil. says

      Hi Michelle,
      Glad you enjoyed the article. I hope that by now you’re feeling a lot better. It IS easier to fast when your body is on board with you – and I’m sure that your body was glad not to eat in order to heal the digestive issue more effectively. It’s also true that most people’s first 3-day fast is their most difficult, simply because the body has to learn how to activate deep ketosis. My advice to you is to keep practising 3-day fasts from time to time until your body learns how to make the switch more easily. It WILL get easier, I promise!
      All the best,

  6. Brad says

    Thank you for the reply, Tallis. What was throwing me off was that the 1 day fast said 36 hours, so I wasn’t sure if you started out with the one day fast (36 hours) and then continued with 24 hours, or if each day of the fast was considered 36 hours.

    Anyway, you clarified for me and I appreciate it! I’m currently in the middle of the 36 hour fast and will definitely be reaching out to you for private coaching when I decide to do a longer fast.

    Have a wonderful day and thank you for all of the incredible content you provide!

    Best regards,

    • Tallis Barker, D.Phil. says

      Aha, I understand the confusion! Glad it’s resolved now.
      All the best on your current fast,

  7. Brad says

    Hi Tallis, so is the 3 day fast 36\24\24 or 36/36/36?

    • Tallis Barker, D.Phil. says

      Hi Brad,
      I’m afraid I don’t understand what you mean… It’s three days, ie 72 hours, and some people like to ‘sleep on it’ at the end of the third day, breaking the fast the following morning at 3.5 days, ie @84 hours.
      Hope this clarifies things!

  8. Rick says

    What type of water should I drink on a water fast? Distilled? Mineral water? Spring water?

    • Tallis Barker, D.Phil. says

      Hi Rick,
      I wouldn’t worry too much about this question. If the water you drink in everyday life doesn’t kill you, then it won’t during a fast either! Of course, having said that, it’s always nice to try to find a good quality source of drinking water (in both everyday life as well as while fasting). Personally, I prefer spring water because it’s the most natural. Distilled water may be the purest, but it’s certainly not natural and it does taste rather ‘dead’. During a water fast, you may be glad for any variety in the taste, so maybe you should try out all of the above and see what you like best!

      • Rick says

        Thanks for your quick reply Tallis! I’ve been drinking distilled water for the past 5 years or so. It’s tasting worse and worse every day and I clean the distiller regularly. Yes, it does taste dead. My body is starting to rebel against it. LoL. I bought 6 gallons of spring water recently to see how my body would react and it loved it. It tasted great and my body was happy with it. It costs too much for everyday drinking, but when water fasting I’ll drink spring water only. I may not have to add an electrolyte like salt either because spring water has minerals in it naturally.

        I think you’re doing an AWESOME work by coming on here and helping people with your expertise. I’m glad that you are alive and upon planet Earth.

        • Tallis Barker, D.Phil. says

          Thanks Rick, it’s a privilege to be able to help people!
          (And by the way, for 99% of people there’s no need to add electrolytes during a water fast, so long as you drink to thirst!)
          All the best,

  9. Katrina says

    How often can one do a three day fast? I just did one. It was definitely harder the last day. I was going to do seven days but thought for my first time that three days was fair as I need to do more research.

    I’m wondering how often it’s safe to do a three day fast in preparation for a seven day.

    Thank you

    • Tallis Barker, D.Phil. says

      Hi Katrina,

      Thanks for your question. Let’s put it this way, you could do a 3-day fast every week indefinitely, and it would still be safe so long as you’re eating a nutritious diet. I once had a client who was suffering from terminal cancer, and had been given a few weeks to live by the doctors. She did a 3-day fast every week and combined this with a highly nutritious anti-cancer diet, and she was still going strong 18 months later (when we eventually lost contact).

      So the limitation here is really psychological not physical. It’s important not to build up resistance to fasting by pushing yourself too frequently beyond what you’re willing to give up, in terms of the comfort of food. Only you can know the answer to that!

      All the best,

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