Water Fast Coaching and Articles

Dr. Tallis Barker, D.Phil., Nat.Dip., NA.Dip., Naturopathic Water Fasting Consultant & Coach

3-day water fasts: cleansing, ketosis and metabolic change explained

Expert Water fasting coaching with Dr Tallis Barker? D.Phil, Nat.Dip

Your first 3-day water fast is a major step into therapeutic fasting. It’s the point where your body begins shifting from sugar-burning to ketosis, awakening your natural healing metabolism. But it’s also where most first-time fasters meet their biggest challenges—both physically and emotionally.

If you’re new to this, you might have some immediate questions. Here are quick answers to the most common ones:

Your body switches from burning sugar to burning fat (ketosis), triggering healing and detox. This usually starts after 36–48 hours.

Glycogen runs out, but full fat-burning hasn’t kicked in yet. This “in-between” phase can cause fatigue, aches, or low energy.

Only minimally. The body uses amino acids briefly, but not whole muscle tissue—and once ketosis is established, this stops.

Headaches, body aches, nausea, and fatigue—especially around the lower back—are all normal. They pass as your body adjusts.

Start gently with juice, then light fruits or vegetables. Don’t overeat—your digestion needs a slow restart.

CONTENTS:

Introduction
Why the 3-day water fast is your gateway into therapeutic fasting and how it unlocks your healing metabolism.

Benefits and Challenges of a 3-Day Water Fast
How your body shifts into ketosis, why this matters for detox and energy, and what makes the first few fasts especially demanding.

What Happens During a 3-Day Water Fast – Day by Day
A detailed guide to the physical and emotional changes of each fasting day, with practical insights to support your experience.

  • Day 1: Easing In
    Glycogen depletion begins; emotional resistance may soften if you’ve fasted before.
  • Day 2: Metabolic Crossover
    Glycogen runs out, ketosis begins—but symptoms like fatigue, aches, and detox may peak here.
  • Day 3: Turning the Corner
    Ketosis stabilizes, energy may start to return, and the healing metabolism is now fully active.

Refeeding After a 3-Day Fast
How to break your fast safely with light meals, avoid common pitfalls, and support digestion as you return to eating.

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Introduction:

On the journey into water fasting, your first 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 for moving on to longer fasts (such as the 7-10 day water fast and more prolonged fasts), in which much deeper healing can occur. The more you practise the 3-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 my 3-day water fast Online Course. For those who need more personal contact, I also offer online consultations and coaching.

Dr Barker regularly speaks at international conferences on water fasting. Below you’ll find his lecture for The Real Truth About Health conference, as well as a panel conversation with Dr. Alan Goldhamer – one of the most recognised names in the field.

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 benefits and challenges 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 metabolic process of burning fat mobilised from adipose (fat) tissue in the form of ketones and fatty acids. 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. (And even if you do follow the lowest possible carb diet – which in most cases is certainly not advisable – the depth of fasting ketosis far exceeds that of dietary ketosis.)

In short, the vast majority of people never experience deep 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/digesting, 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.) However, unless your body has a lot of fat that it’s happy to burn, you probably won’t feel this energy going out into everyday strength and stamina. Instead, your body is more likely to want to turn it inward for cleansing and detox – which can easily leave you feeling weak and drained on the outside.

Second, because you’re drawing on the fuel in your fat cells, you also gain the potential to break down and cleanse the fat-soluble toxins which have been locked in there for years and years, safely sequestered away from interacting with the rest of your body. This is a different mechanism from being on a low-carb diet, because in this case essentially the same surface-level fat cells are used for energy, over and over, from meal to meal. In contrast, deeper levels of fat usually remain untouched, with the toxins of life continuing to accumulate within. This is reflected by comparing the ketone levels of someone on a low-carb diet with those of someone on a water fast. Not surprisingly, ketone levels while fasting are much, much stronger!

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

Day 1:

On a purely physical level, the first day obviously feels the same as it does on a 24 hour fast (described in greater detail here). During this period 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, if you already have experience in surviving one day without food, you should feel much more comfortable. 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 your body. 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 (as can happen the first time you fast for 24 hours).

The webshop offers downloadable fasting plans and guides to help make your water fast a success.

Day 2:

By the beginning of the second day your glycogen reserves will almost certainly 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: the remains of my usual carbohydrate-based metabolism, as well as by fasting 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!

ONLINE COURSE

Complete a 3-day water fast

This video + pdf bundle provides you with all you need to know in order to safely, successfully and smoothly carry out your first 3-day water fast. If you already have a little experience, there are plenty of additional tips to help you go deeper into water fasting.

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 search for an alternative power source – and quickly too! Ultimately, 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 biochemical reactions and hormonal parameters which mediate those reactions are so different from what you’re normally used to.

Instead, following the depletion of glycogen within the first 24-36 hours of a fast, the next closest source of energy is found by breaking down the building blocks of protein. This comes from metabolising amino acids. By stripping off the nitrogen molecules common to all amino acids it is possible to synthesise glucose, which can then be burned in the usual way within the mitochondria of each cell. This process of converting amino acids to glucose takes place primarily in the liver through a process called gluconeogenesis.

Although all cells across the body contribute the amino acids necessary for gluconeogenesis, it’s true that muscle cells generally store more amino acids than other types of cells. But don’t worry: contrary to a lot of well intentioned but misinformed information out there on the internet, this doesn’t mean that you’re going to lose any significant muscle mass. Rather, we’re talking about the loss of only amino acids – not the actual autophagy of whole muscle cells. And in any case, once your body has started to perfect ketosis in the days ahead, the continued need to metabolise proteins becomes increasingly minimal.

In the meantime, you’ll probably continue to feel low on energy. Your muscles may ache, especially in your legs and glutes. 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 lower back are also common, as your kidneys and lymphatic system start to work overtime, flushing out the first toxins from your fat cells as well as the extra acids caused by metabolising protein. All of this can be enough to elicit nausea as well. In the face of such detox symptoms, 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 – and especially if you have the mental energy to do so – then by all means continue your fast! 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, I’d recommend taking on a longer, more cleansing fast once your body and mind have more fully acclimatised to and made friends with 3 day fasts. The most important thing here is to build up a stable, positive, long-term relationship with fasting. There’s no need to rush ahead, unless you have an urgent health issue which requires a more extended fast immediately.

Refeeding:

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 within a day or two.

After breaking a longer fast, though, it’s extremely important to follow a well structured meal plan.

How to break a water fast?

If you return too quickly to a normal diet, you risk encountering both digestive problems as well as ‘refeeding syndrome’. This is a potentially fatal complication caused by the change from ketosis back to your everyday metabolism. If you have any doubts, I offer a downloadable 86-page PDF which covers refeeding for any length of fast.

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384 responses to “3-day water fasts: cleansing, ketosis and metabolic change explained”

  1. is it normal to have diarrhea during a 3-day water fast?

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      Hi Shahenaaz,
      It can be normal, and it indicates a lot of toxic build-up in the gut. After only three days this is probably due to problems with diet before the fast.
      All the best,
      Tallis

  2. Hi Tallis

    Great article and I’m really interested in trying fasting to help in resolving some current issues I am struggling with. May I ask if you think moving towards a longer fast might help me.

    I have been struggling with head pressure, tinnitus, headaches and neck stiffness since a Covid booster vaccine in December 2021. I’ve tried everything and nothing has helped. Time may be a healer but I feel I need to help in some way.

    What do you think?

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      Hi Scott,
      Thanks for your question. I’ve worked with numerous clients who have experienced health problems due either to Covid vaccine injury or Long Covid itself, and I can tell you that water fasting is extremely powerful in resolving these issues. The vast majority of my clients reach either a full healing or a significant healing (which can be improved upon in future fasts). If you need support, you can reach me via the contact form on the coaching page of the website:
      https://waterfasting.org/online-coaching-and-consultations-for-water-fasting/

      All the best,
      Tallis

      1. Alyson Whitworth Avatar

        Thank you for this article and response. I am also having some Covid vaccine issues which is causing chest pressure and numerous other issues. I am day 1 of a 3 day water fast. I have hear several places that water fasts can help a lot. How often should I do 3 day water fasts? Once a month? or more?

        Thank you!

        1. Tallis Barker, D.Phil. Avatar
          Tallis Barker, D.Phil.

          Hi Alyson,
          Thanks for writing. Yes: in my experience, extended water fasting is definitely the most powerful thing you can do to heal from Long Covid or Covid vaccine injury. In terms of 3-day fasts, a lot is going to depend on the severity of your case. Some people can heal using only 3-day fasts, while others need considerably longer: in the region of 21+ days. The frequency of 3-day fasts is essentially up to you. For example, I sometimes work with cancer patients who have to do a 3-day fast every week. This is not to suggest that such a protocol would be best for you (especially given the reasons that you’re fasting), but simply to note that psychological considerations usually limit how often someone is willing to fast.
          Hope this helps,
          Tallis

  3. Hi, I just completed a 3.5 day water fast (+some salt, because my body felt it needed it) and found it incredibly easy. Nice to know, and I would have extended to a longer fast if not for social reasons.
    I’m wondering what you know about the relationship between fasting and the menstrual cycle – is there a preferred phase of the cycle to fast in, how many fasts per cycle would be safe, etc.
    Thanks!

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      Hi E,
      Thanks for sharing. Glad water fasting feels easy. To answer your question: yes, fasting does interact with the menstrual cycle, but in terms of preferred phases or how frequently to fast, it all depends on how long you’re planning on fasting. In general, fasting (especially extended fasting) brings the menstrual cycle into greater balance over the long term, but you may end up missing out on the period part of the cycle. If you think of the monthly bleed as a cleansing process, the cleansing of a water fast will often remove the need for a women’s body to cleanse via a period. Even if you don’t bleed in a given month, though, that doesn’t mean that you’re not going through the usual cycle of hormones over the course of the month.
      Hope this helps,
      Tallis

  4. 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

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      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,
      Tallis

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

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      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,
      Tallis

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

  6. 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!

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      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,
      Tallis

  7. 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.

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      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,
      Tallis

  8. 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.

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      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,
      Tallis

  9. 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,
    Brad

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

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

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

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      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!
      Tallis

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

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      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!
      Tallis

      1. 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.

        1. Tallis Barker, D.Phil. Avatar
          Tallis Barker, D.Phil.

          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,
          Tallis

  12. 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

    1. Tallis Barker, D.Phil. Avatar
      Tallis Barker, D.Phil.

      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,
      Tallis

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