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

36-hour water fasts: a beginner’s guide

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

CONTENTS:

  • Introduction
  • The benefits of a 36-hour water fast
  • Beyond the 36-hour water fast
  • Dietary preparation and refeeding

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Introduction:

Most people in the modern world have never gone a whole day without eating. You too? If so, a 36-hour water fast is the perfect way to begin your journey into water fasting.

I remember when I did my first water fast many years ago. The plan was to eat dinner, then fast through all of the following day, breaking my fast with breakfast on the day after this. This format is ideal for anyone wishing to try out a 36-hour fast.

Psychologically, the experience was hugely challenging. Like most people, I’d hardly ever even skipped a meal in my life, and the idea of not eating anything for a whole day seemed almost inconceivable. Every time my stomach rumbled, it felt like the end of the world: I was going to starve! Of course, logically I knew that I wouldn’t, but the rational mind so easily collapses when your deeper, instinctive emotions emerge from out of the subconscious. By the evening, all I could think about was food – and then to make matters worse, I had to go to bed on an empty stomach…

In the end, though, I did it. And so can you. Anyone can survive 36 hours without food!

So why put yourself through such a terrible ordeal 😉 ? (By the way, contrary to my own experience, many of my clients do actually enjoy their first fast, feeling full of energy and without existential worries.)

The benefits of a 36-hour water fast:

There are at least four important reasons to face your fears and reap the benefits of a 36-hour water fast.

1.

The first reason is psychological. Precisely by facing your fears and emerging victorious on the morning following the fast, you become a stronger person. We all have a built-in survival response. By breaking the psychological barrier of no food for a whole day, you’ll find that the next 36-hour fast goes much more smoothly. Equally important, almost all my clients find that this empowers them to move on to longer water fasts in which the body’s healing metabolism can be unlocked more fully.

2.

The second reason to practise 36-hour fasts is physical. You give your digestive system a break for a whole day. It can rest and recuperate. This is hugely beneficial for maintaining health and to prevent aging. To a degree, intermittent fasting (time-restricted eating) elicits many of the same benefits, but 36-hour fasts takes this to the next level. In particular, you give your stomach, liver and pancreas much more downtime from having to synthesize digestive enzymes, a process which otherwise consumes a high degree of biochemical energy. To put it in perspective, a 36-hour fast gives your digestion double the rest time of most intermittent fasting protocols. In addition, this also means that other well-known benefits of intermittent fasting – such as the stabilisation of blood glucose (along with reducing insulin resistance) – can go much further by practising 36-hour fasts.

3.

The third reason bridges physical and psychological factors. A 36-hour water fast gives you the first opportunity in your life to truly experience ‘going to bed on an empty stomach’ on the second night of the fast. Just as it was a big deal for me the first time, so most of my clients find the same. Even people who practise OMAD (one meal a day) don’t really have to face this fully. Although the idea of the proverbial empty stomach may feel a little frightening for the first time, it’s also a hugely important rite of passage. By the second night of a 36-hour water fast, your glucose levels will have significantly dropped after 24 hours of fasting. This is because your body has exhausted its supply of both dietary sugar directly from the GI tract and digestion, as well as energy from a stored form of sugar called glycogen, which is held mainly by the liver and in muscle tissue.

For many people, this depletion of carbohydrates at around the 24-hour mark sets off psychological alarm bells which can make it hard to go to sleep the first few times. If this happens to you too, know that you’re not alone, and that it will resolve with enough practice. For instance, when I fast now, I sleep like a baby at this point – precisely because blood glucose is low, and so there’s not much energy in the body to keep me awake! (continued below)

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Beyond this issue, the ‘need’ to go to sleep with a full tummy often relates to deeper psyschological issues relating to feelings of insecurity and safety. Through practising 36-hour fasts, you come to realise that it’s okay: you really don’t need all that food to feel safe enough to fall asleep. In fact, when you’re free of emotional baggage, going to sleep on an empty stomach can actually feel surprisingly quiet and calm, given that there’s no active digestion taking place behind the scenes.

4.

Fourth, and perhaps most importantly, fasting for 36 hours means you prompt the body to begin unlocking its healing metabolism. First and foremost, the drop in blood glucose levels triggers ketosis: the process through which your body draws on the fatty acids held in adipose (fat) tissue as a source of fuel, now that the carbohydrates which usually power your body have become depleted. (This process is described more fully in the article on the 3-day water fast.)

There are multiple reasons that you can heal while in fasting ketosis. Firstly, the body sequesters and stores many fat-soluble toxins in adipose tissue, where they can’t interact with other cells of the body, thereby causing damage. It is only through fasting ketosis – through drawing on the fatty acids stored in adipose tissue – that these toxins can also be released and excreted from your body. Secondly, after about 24 hours the energy otherwise required for digestion can be redirected elsewhere, which here means towards detox and healing. Thirdly, with no food going in, your body also starts looking for other alternative sources of fuel. This means breaking down both damaged tissue as well as intracellular components which can be degraded and recycled: a process otherwise known as autophagy.

Beyond the 36-hour water fast:

To complete the switch over to fasting ketosis you need at least three days, which is why it’s so important to learn the 3-day water fast at some point. But don’t rush into anything too soon! If you don’t feel ready to fast for three days, keep practising the 36-hour fast. If 36 hours feels too long, then try 24 hours instead. You can begin a 24-hour fast after eating dinner and then break the fast with dinner the next day (lunch to lunch is another option). 24 hours does less to nudge the body into ketosis, but you’ll still benefit from giving your digestion a rest as well as from a level of detox which surpasses anything in everyday modern life. If a weekly or fortnightly 24-hour fast feels too much, then perhaps you should try intermittent fasting instead.

Whatever you do, your body will thank you for it!

There’s always a way forward with fasting, and I’m here to help if you need.

Dietary preparation and refeeding:

One final note: there’s no need to prepare for a one day fast by changing your eating habits beforehand. Likewise, you don’t have to transition gradually back to eating normally afterwards.

Related articles:

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

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141 responses to “36-hour water fasts: a beginner’s guide”

  1. Really appreciate your prompt and helpful reply. Yes I have T2 diabetes. I have been on (increasing) oral meds for about 10 years. Considering the fatigue and stress – I used to teach high school – and my general carelessness with food, drink and sleep I suspect that the T2 started at least 10 years before that. My main aim is to get rid of T2 and the meds. And eventually to stop the other main med I am taking for BP. My BP readings have been between 120/130 and 70/80 for the last five years with meds.
    Starting this week I am extending my 2-day to a 3-day fast. Today (Monday) I am into my second day of fasting and I am going to fast tomorrow Tuesday too and break it around noon on Wednesday, that’s about 3 and a half days, I think. The other half of the week I’ll be on intermittent fast, skipping bf as I mentioned earlier. I hope to continue on this programme the next five weeks and then get to see my doctor who commented at my July visit that I would be driving him out of business.
    Once I have seen the doctor who is actually clueless about what’s happening to me and done my blood work I shall stop the half week fasts and look at prolonged fasts – perhaps this will rid me of the BP meds too.
    Is this three and a half day fast every week harmful in any way especially considering that on the other days I practise intermittent fasting too? I suppose I’ll know in five weeks’ time but what has been the general result of anyone else doing this?
    Incidentally, thank you for your insightful comments on coffee. I am now off it on fast days and manage with green tea and water boiled with some herbs.

    1. I’ve not heard of anyone practising this specific form of fasting, but I don’t see why it should be harmful to you, so long as you’re eating a nutritious diet during the time that you actually are eating. The only minimal problem I can foresee is that every time you initiate ketosis, you need a transitional period to get it up and running after glycogen stores have run out. During this time, muscle becomes the main source of fuel for your body. The more often you fast, though, the quicker and more efficient this transitional time becomes, so I suspect you’re not digging very much into your muscle strength. Just keep track of things. Having to wait for your body to run out of glycogen and then kick-start ketosis (before you can enter “healing mode”) each time you fast is one reason why many shorter fasts are less efficient than a single prolonged fast.
      All things considered, though, it sounds like you have a good plan.
      Your fasting will also help your BP!

      1. S. Radhakrishnan Avatar
        S. Radhakrishnan

        Hi,

        I should have posted this a month ago but there have been many preoccupations.

        Here’s what happened. I had planned to extend my 2-day weekly fast into a 3-day one (as per my plan I wrote about in my last post) but on Day 3 (Sept. 12) I felt quite OK and I decided to continue for as long as I could. I managed to go on for 7 days, surprising myself. I had only water boiled with a few herbs and on two or three days I had some freshly squeezed lemon with lots of water added. No vitamins, no supplements, nothing.

        There was no hunger, no obsessing about food or any of the other ill-effects. associated with fasting. Also there was no particular periods of elation except mild surprise that I was doing it. I stopped on Day 7 for no particular reason but perhaps I was a bit afraid. I was doing this longer fast for the very first time in my life and didn’t want to venture too far into unknown territory. I broke my fast with some vegetable soup and boiled vegetables on Saturday (Sept. 16) evening. Since then I have been on my regular 2-full-day weekly fasts and (no breakfast) intermittent fasts on the other days.

        I lost about 4 kgs in weight. I lost visibly some muscle, mostly in my arms and legs. And a few cms off my waistline. I did not go in for any specific physical activity during the fast except pottering around my house and garden which always needs weeding. I rested a lot, spending time reading and on the computer screen. I was off meds for both my T2 and BP and resumed them at half dose when my fast ended. I had stopped statins and thyroid meds a month ago.

        Today I had my blood work done exactly a month after my 7-day fast. My FBS and PPBS have both gone up but my HbA1C has come down to 5.3%. My lipid profile has improved a great deal but my Serum LDL Cholesterol has gone up to 137.2mg/dl. My BP too has gone up to 130/90. My Thyroid Function Tests show normal results. I have reverted to my old dosage of T2 and BP meds – perhaps I halved them too soon!

        The main reason for the fasting was to get rid of the T2 and BP meds. I know I cannot get rid of them with just one cycle of fasting. I suppose I will have to be patient. I now feel confident about trying a 10-day fast. I am thinking of doing it around mid-December. These longer fasts, how often can they be done? Is there any particular area I need to address that can help me be rid of medication?

        Thanks a lot.

        1. Thanks for the update.
          It’s great you were able to simply extend your planned fast into a full week like that!

          Longer fasts like 7-10 days would normally be enough once per year for regular maintenance and detox in a totally healthy person. In order to deal with T2 diabetes, though, you’d need to consider doing them more frequently or doing a prolonged healing fast of at least two weeks. There’s no ‘rule’ about how frequently you can do 7-day fasts, but it does make sense not to try another one until you’ve regained your weight again and are feeling 100% back to normal. So long as you’re eating healthily in between, it’s unlikely you’ll deplete yourself of vitamins and minerals, so hopefully that shouldn’t be an issue. Personally, I would wait at least double the length of the fast before trying another one, keeping in mind that you’re not planning on doing 7-day fasts for the rest of your life (!) but rather for a limited number of times in the future in order to deal with a specific problem.

          You may also want to consult with your doctor about gradually lowering your meds in tandem with the fasts. You don’t want to suddenly just drop them! Nor does it make sense to keep them artificially high if your body’s sensitivity to insulin gradually returns to normal through the fasting.
          Hope this helps,
          Tallis

  2. I’m 66, on oral meds for diabetes. Starting early May 2017 I embarked on a 24-hour water fast every four days. The other days I had the usual three meals trying to go low on carbs. In mid-July my doc stopped one of my meds. Starting August I switched to intermittent fasting, having dinner between 7 and 8 pm, skipping bf the next day and having lunch between 1 and 2 pm. I also changed my fasts. After dinner on Saturdays I fast all Sunday and have dinner on Monday between 7 and 8 pm. I have no discomforts of any kind with the fasting. I am planning to increase my 2-day fasting to 3. that is, after Saturday dinner I fast all day Sunday, Monday and Tuesday and break my fast on Wednesday between 1 and 2 pm. Do you think this is a good idea? How long can I do this – if I did venture on this path?

    1. Hello,
      Thanks for sharing. Is your goal to cure yourself of diabetes? (Type 2, I assume)
      If so, it already sounds like you’ve made progress if your doctor has stopped one of the meds. That’s great news!
      It sounds like you have a well planned regime worked out, with things moving forward at a steady pace.
      One option would be to continue this way, gradually lengthening out your fasts and doing them at a frequency which feels manageable and not too much like a chore.
      The other option – given how easy it sounds like you find water fasting – would be to do a single prolonged healing fast, subsequently backing it up by more regular short fasts (perhaps a weekly 36-hour fast) until you’re absolutely sure that you’ve beaten the diabetes. In general, this approach tends to more dramatically improve symptoms in most illnesses (including diabetes), if not cure them completely in one feel swoop. I’d check with your doctor first, though – assuming, of course, that your doctor understands the benefits of fasting (which unfortunately most still don’t!!!).
      If the idea of a prolonged healing fast feels too daunting, it already sounds like you’re making good progress on your current path.
      All strength and good health to you,
      Tallis

  3. Hi! Thank you for the resource. It has been very motivating in trying my first 36 hours fast. Would you advise against naturally flavored waters during fasts? I’m thinking of La Croix waters, which I’ve been having.

    Their website states: “The flavors are derived from the natural essence oils extracted from the named fruit used in each of our LaCroix flavors. There are no sugars or artificial ingredients contained in, nor added to, these extracted flavors.” In short, no sweeteners, no salt, no additives.

    1. Good question, Simon. It’s totally up to you. In any case, the natural essential oils won’t interfere with the biology of the fast.

      If it’s your first 36-hour fast, then why not be kind to yourself and enjoy whatever water you want to drink. You can always go more ‘hardcore’ later if you feel like it, challenging your ego with just plain water. On the other hand, you may find that your body rejects the aromatic scents of flavoured water, preferring the purity of plain H2O (although this is more likely to happen during a longer fast).

      However you choose, congratulations on your first 36-hour fast!
      Tallis

    2. Totally agree with Tallis.. I had couple of cups of coffee during initial couple of weeks and then switched to green-tea only after that…

  4. Would once a week 36-hour water fasts be enough to get any benefit (like every weekend)? Or does it have to be done more frequently…?

    1. Hi Anthony,
      A weekly 36-hour fast is perfect for regular “maintenance”. Just like a weekend gives your mind/body some rest time from your job, so the same applies to your digestive system. If you’re inspired to do more fasting, then rather than do several 36-hour fasts per week I would occasionally consider doing an additional longer fast to go deeper into detox.

  5. Would once a week 36 hour fasts (e.g. like every weekend) be enough to get any benefits? Or would it have to be more frequently?

  6. I normally drink 8oz coffee (black) twice during my 36hour fasting.. I also take 8oz tea twice. Do coffee and tea intake affect the 36-hour fasting negatively in anyway?

    1. Hi,
      Hmmm, lots of caffeine there :-).
      If you ‘need’ caffeine during your fast in order to avoid headache withdrawal symptoms, I’d definitely recommend drinking green tea during the duration of the fast instead of black tea or coffee. Coffee strongly stimulates your stomach acids – precisely at a time when you’re trying to give your digestive system a rest. The tannins in black tea do the same to a lesser degree, and if you add milk to your tea, then you’re throwing even more digestibles into your stomach.
      Green tea can give you caffeine with no calories, while alkalising your system (which contributes to detox). In fact, the Japanese and other cultures sometimes practise green-tea detox fasts.
      If your ultimate goal, though, is to allow your body a rest through fasting, then any source of caffeine is a stimulant which will work against this.
      Hope this helps,
      Tallis

      1. Thanks for the response! This really helps… I don’t have headaches etc during my fast.. I drink coffee just out of habit and as means to feel full 🙂 I don’t add milk to my tea.. As you suggested, I will stick to Green Tea.. What do you think about other tea options like Herbal tea, Indian Chai (that has spices) etc.. Of course, all without additions like Milk…

        1. Habit is one step away from addiction, but that’s another question 🙂
          Glad you don’t get headaches (another sign of addiction!).
          Indian chai is basically black tea with spices, so from a physical perspective it acts similarly to plain black tea, although there does tend to be less black tea in most chai mixes than plain black tea.
          Herbal tea is caffeine-free, and certain types of herbs can be used to help the fast, such as nettle tea (which stimulates and detoxes the kidneys).

      2. One more question… I sometimes play Tennis for 2 hours in the evenings on fasting day.. First couple of fasting days I had salad and some protein before the Tennis matches.. Yesterday (my most recent fasting day) I stuck to water only fasting and I played fine… What is your recommendation for such scenarios where heavy physical activity is involved during fasting day?

        1. Hang on, you said: “First couple of fasting days I had salad and some protein before the Tennis matches.”
          Fasting means no calories. You mean you were dieting?
          Whether dieting with reduced calories or fasting with no calories, I’d say there are no fixed recommendations except to listen to your body. If you find yourself more easily out of breath or weaker, then respect your limits!

  7. Tallis,
    I would like to know if ,say walking 10 miles per day and doing a 36 hour water fast would put you into a state of ketosis faster than a 72 hour water fast with no exercise

    1. Hi Thomas,
      The answer is yes and no…
      On the one hand, absolutely right about the idea of walking long distances to accelerate the progress of a fast. Gentle exercise like walking (IMPORTANT: while fasting, never exercise to the point of getting out of breath!) will also help to expel toxins from your blood stream and reduce any muscle soreness resulting from toxin build-up in the muscles.
      On the other hand, walking 10 miles will burn only about 1000 calories, whereas you’ll burn more than twice that amount with no exercise over the extra 36 hours of a 72 hour water fast. In order to experience the healing effects of a fast, you have to get your body into ketosis by first burning up your body’s glycogen supply – and this runs to about 2000 calories. Not only will the 72 hour fast burn more calories overall, it also allows your body more time to deepen into ketosis and, in doing so, reach a deeper level of detox.
      If you want the greatest benefit, then do a 72 hour (three day) water fast while walking 10 miles a day 🙂 – at least if all that walking doesn’t tire you out!
      (If it does, then walk less, even if it’s just a couple of miles a day.)
      Cheers,
      Tallis

      1. Thankyou, I will try 7 miles walking +72 hour fast.

  8. I just decided to fast for 36 hours for a different reason all together, mostly to calm my racing mind (the ego runs wild sometimes). Food affects me in a negative way sometimes. I wonder if a very low carb diet for two days and then a 36 hour fast can have the same effect as a three day fast? I am already on a low carb diet.

    1. Hi Denis,
      Good question. Whether or not the kind of fast you suggest will “have the same effect” as a three day water fast depends on what you mean by “have the same effect” :-). In terms of ketosis (fat burning), the effect will certainly be similar because you’re already on a low-carb diet. The full effects of a pure three-day water fast, though, will go much deeper. First, you’re giving your digestive system a complete rest and period of rejuvenation. Second, you’ll experience a much greater degree of detox, because during the fast you’ll be drawing fully on the energy of fat cells (which contain toxins) rather than the energy of fat in food. The fact that you’re already on a low-carb diet will allow you to make the switch to full ketosis much more rapidly than someone on a standard diet, and so you’ll be able to spend more of the three days in deeper detox.
      Speaking from experience, your racing mind will also respond much more effectively to a full three day fast than just a 36 hour fast.
      Go for the three days if it doesn’t feel like too much of an emotional challenge!
      All the best for your fast – whichever version you decide to try,
      Tallis

  9. Sarabjeet Khurana Avatar
    Sarabjeet Khurana

    I ll complete my first 36 hour water fasting tom morning…

    Please tell me more about the 3 day fast so that i can start to prepare for the same …

  10. I have done 24 hours fast for 3 days like diner to diner and now i am gonna go for fasting which will be dinner to day after tomrw diner is this fine to do.?

    1. So in other words you’ve been eating once a day for the last three days? This is technically the most extreme form of intermittent fasting, and, if it feels right, can be continued for much longer than just three days in a row (so long as you’re getting all your nutrients and enough calories). In fact, in the past, it was totally normal in many cultures for the regular diet to consist of only one meal. Certain Buddhist traditions continue to practise this, and there may well be others too.
      If you want to add on a longer fast now, it’s completely fine. Are you thinking of a 36-hour fast now?

  11. Very logical and informative…many people I hope become inspired by your article to try a day without food. What are your thoughts on breathatarians who live for years without food and claim to get there energy from the sun, meditation, and pranayama breathing?

    1. Thank you for your kind words :-). What are my thoughts on breatharianism? Well, first, I have no doubt that there are many frauds out there, but it’s also a documented scientific fact that certain people are able to live without food and water, at least for periods of time. To give an example, Prahlad Jani – who was hermetically sealed in a hospital room for a couple of weeks for observation – is only the most recent of these. This wasn’t a case of ‘normal’ fasting, because he showed no sign of weight loss or lethargy. Over the years, yogis and sadhus have repeatedly demonstrated that it’s possible to draw on energy beyond that explained by Western science. The only question is whether you’re able to access that energy (kundalini) or not. (For most people, of course, the answer is no!)

      1. Wow Tallis,
        It seems your knowledge in this topic is very deep because I am going through your articles and find that your knowledge about “Prahalad jaani” is accurate and denote your deeper interest about many other aspect apart from nearly water fasting..

        Prahlad jani is living miracle among many others in india.
        Western science is not able to decode indian knowledge almost in every field (but it is very very very limited and disappearing).
        Western science is meraly 150-500 years old only…….. And indian spiritualism and knowledge is 40000 or more years old as “ayurveda”
        Many others things are more than 5000-10000 years old
        Like
        Yoga
        Astrology
        Math
        Surgery
        Hinduism
        Buddhism
        Shivambu
        Tantra
        Mantra

        And many more……..

        I read and heard that our human body is self sufficient and much more powerful than any creature in this universe.

        I really appreciate and
        @ THANK YOU @ for this valuable blog to uplift humanity by helping and motivating others to become fit and healthy without any expenses.👏👏👏👏👏

      2. Hi thanks for everything.
        So your saying if I do 36 hours fasts twice per week, I might never really burn fat because it requires 3 days or so to enter ketosis!!! Is that true ?? Then I think that from the perspective of losing fat , 36 hours fasts do almost nothing right ????

        1. Hi Jai,
          It all boils down to how much you fast and how much you eat afterwards.
          From the perspective of losing fat, 36 hour fasts do almost nothing in terms of burning fat directly because, as you say, you’re not really entering ketosis. But if you don’t eat extra calories on the other days, you’ll slowly lose weight because your body will have to start to rely on burning fat cells in order to compensate for the lower overall intake of calories. The main benefit of 36-hour fasts is the rest it gives your digestive system. Rather than hoping that fasts alone will fix things – because they rarely ever do when it comes to weight loss! – I would concentrate at least as much on finding a long-term healthy diet which appeals to you, as well as using regular aerobic exercise to burn calories and raise your overall metabolic rate.
          Glad you’ve enjoyed the articles 🙂
          Tallis

      3. I thought I may submit my stats too..
        165 centimeters, male, 77 kg.. With the omron machine, my muscle was around 30% and fat around 29%.. My bmi is 28.6
        Will two 24 hours fasts per week help me lose the 13 KGS I have got to lose?? Or should I do more??
        Thanks so much to you and for all the wonderful articles..

  12. I am doing it and I feel very energetic.

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