Water Fast Coaching and Articles

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

14–40 Day Water Fasts: Healing Power, Benefits & Risks

Why would anyone fast for two weeks—or more?
For those seeking the deepest levels of physical, emotional, or spiritual healing, a 14–40 day water fast may offer what shorter fasts cannot. Once your body has fully adapted to ketosis, longer fasts allow for profound detoxification, immune recalibration, trauma release, and sometimes even the reversal of chronic illness. However, they also require care, preparation, and guidance.

In this article, you’ll learn what happens in extended fasts, how to prepare and refeed, and how to distinguish between a true healing crisis and signs that it’s time to stop.

Note: Extended water fasts of 14–40 days are powerful but demanding. They should never be undertaken without expert supervision, especially if you have chronic health issues, take medications, or are unsure of your body’s limits. Always consult your doctor before beginning any prolonged fast. This article is for educational purposes only and does not replace medical advice or personalised coaching.

To address chronic illness, deep trauma, or long-standing toxic load—levels that shorter fasts usually can’t reach.

Yes—if done without guidance. Extended fasts can deplete fat, protein, or electrolytes if pushed too far.

A temporary flare-up of past symptoms as the body clears deeply stored illness. It can be intense but is often part of the healing.

If true hunger returns, or signs point to electrolyte imbalance, it’s time to break the fast safely.

Very slowly and intentionally, with light plant foods. The longer the fast, the longer the refeeding process should take.

CONTENTS:

  • Introduction
    Why extended fasts are rare—but sometimes necessary—and what makes them so powerful.
  • Benefits of Extended Water Fasts (14–40 Days)
    How deeper fasting supports chronic illness reversal, detox, and complete healing.
  • Physical, Emotional, Spiritual Healing
    What happens beyond the body: trauma release, ego dissolution, and ancient fasting traditions.
  • Experiencing a Healing Crisis
    When old symptoms reappear—and how to know whether to continue or stop.
  • The Dangers of Fasting Too Long
    Understanding the risks: fat/protein depletion, electrolyte imbalance, and misreading hunger signals.
  • Refeeding After an Extended Fast
    How to break a long fast with safety and care—and why this step is just as important as the fast itself.

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Why in the world would you ever want to fast for two weeks or more?

If only a tiny percentage of people in the Western world ever undertake a water fast of any kind, then only a tiny percentage of people who water-fast will ever undertake an extended healing fast of 14 days or more. Why? There’s simply no need. For everyday cleansing and healing, occasional 7-10 day fasts combined with regular short fasts such as the 3-day or 36-hour water fast should keep you in excellent health.

Benefits of extended water fasts (14-40 days):

However, in order to reach the deepest possible level of healing and reap the greatest benefits, it is necessary to dig deeper with a longer fast. For instance, certain serious physical illnesses – those often deemed incurable by Western medicine – require the cleansing of an extended fast in order to permanently heal.

Despite what most modern medical doctors may tell you, conditions as wide and varied as Long Covid, gut issues (such as IBS, ulcerative colitis and food intolerances) adrenal issues (CFS/ME), diabetes, chronic high blood pressure, autoimmune disorders (including allergies and asthma), as well as certain types of tumors are all potentially curable. I know this for a fact, because I have personally worked with clients suffering from ALL the health issues listed above to the point of a full healing.

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.

As a water fasting coach, I’m privileged to witness this miraculous healing potential of the human body every day! It does take time, though, and in order to heal effectively from chronic illness, the length of the fast must typically last 14-40 days.

In helping clients decide how long to fast, three main factors come into play.

First is the overall symptom picture – that is, the sum total of active health issues, all of which constitute a toxic load contributing to illness. Although, for example, someone may wish to fast in order to heal Long Covid, further questioning almost invariably reveals other health issues in the background, both past and present. Whether presenting with symptoms of their own or whether entirely sub-clinical and ‘invisible’, these apparently secondary issues tell a story of how, over the years, a client has arrived at the present moment.

The second factor which suggests how long a client may need to fast is the strength of their immune system. The primary factors here are age, diet, stress and, in the case of chronic illness, how much the immune system has already been worn down in fighting a war of attrition.

The third factor concerns the degree of prior cleansing – and especially water fasting. Quite simply, the more you’ve already fasted, the more quickly and powerfully your body can mobilise your immune system for healing.

Physical, emotional, spiritual healing:

Beyond physical healing, the deepest emotional and spiritual cleansing can similarly take place only through the sheer length of an extended fast. In fact, what I’ve seen over many years of coaching is that in order to achieve the greatest physical healing, it’s also necessary to surrender emotionally and spiritually to the whole process. A big part of my job is to help facilitate that process.

Although nowadays we tend to remember only the Biblical 40-day fasts of Moses and Jesus, the fact is that many spiritual traditions over the millennia have demanded 40-day water fasts. Even Pythagorus required potential students to undertake a 40-day fast before he was willing to accept them. As much as we balk at the idea of giving up food for such a long time, it’s mostly just a question of unwillingness to forgo the addictions and pleasures of life. Don’t believe the voice of your fears and reluctant ego. You won’t starve to death.

Unless you’re seriously malnourished and underweight to begin with, you carry the better part of 100,000 calories on you, locked in your fat tissue and waiting to be released through ketosis. That’s enough to last you well over 40 days. If you’re overweight, you could potentially fast for much longer (although in most cases this is not advisable).

In other words, getting through a 14, 21 or 40-day fast is often a mind game more than anything.

Letting go of your fears about fasting is just the beginning. The process of surrender also eventually leads to the release of pent-up, self-destructive emotions and, for some people, a catharsis of trauma from the distant past. In doing so, you’ll free yourself: discovering a place of inner calm and spaciousness where you can finally breathe. This is a hugely important part of the healing process.

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

Experiencing a healing crisis:

Although in one respect an extended fast simply continues the notion of a 7-10 day water fast, it is also much more powerful because it gives you the opportunity to experience deeper ‘healing crises‘. As described in the article on the 7-10 day water fast, a healing crisis often occurs towards the end of the first week of water fasting, as the symptoms of old illnesses, injuries and traumas resurface, before being permanently expelled from your body.

A similar process often occurs around the end of the second week of fasting – and this is the reason that if you decide to extend a 7-10 day water fast, it’s worth aiming for at least 14 days. This second healing crisis tends to call forth deeper issues than the first healing crisis, or, alternatively, finishes resolving those issues which were not fully cleared during the first healing crisis. In other words, it’s from the beginning of the second week of water fasting that your body can begin to heal from more serious health issues. Simply, up until this point, your body has been focussed on cleansing the toxins of everyday life (and especially so if you haven’t been fasting regularly).

For the deepest and most serious health issues, healing crises often occur much later into the fast, whether 20, 30 or even 40 days. There’s no way to accurately predict when they will occur. You can only trust your body and let nature take its course…

Occasionally, healing crises can be extremely intense, especially when they occur late into a fast. When this happens, it’s critically important to be able to tell the difference between a healing crisis and a sign from your body urging you to stop the fast. This is where working with an experienced water fasting coach can really help. If it’s a healing crisis, you should ideally try and push through. If it’s not, you should stop immediately! (continues below)

Not every healing process is accompanied by a dramatic healing crisis. Sometimes symptoms of illness and trauma simply begin to disappear. In cases like this – when no clear sign indicates that you’ve obviously freed yourself from a health issue – it can be difficult to know when to end the fast. This is another reason why it’s advisable to consider undertaking an extended fast with the help of an expert who understands the subtleties and symptomatology of fasting. The other main reason for working with a professional is to make sure you don’t overstep your body’s nutritional capabilities, as a prolonged fast begins to reach its physical limits.

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The dangers of fasting too long:

  • Depletion of fat (adipose tissue)
  • Depletion of protein (amino acids from muscle tissue)
  • Depletion of electrolytes

If you continue fasting indefinitely there comes a point where the fast turns into starvation. You obviously don’t want to overstep this mark! For when your fat stores are finally depleted, the body has no choice other than to devour muscle tissue, as well as feed from your inner organs. You’ll do yourself serious damage. Fortunately, though, the body sends a clear sign: extreme hunger. Although it’s unlikely you’ll miss this red flag, it’s also true that normal periods of hunger can develop during an extended fast. The urban myth out there on the internet – that hunger simply disappears on the third day – is a gross oversimplification of what actually happens. On longer fasts, it isn’t uncommon for my clients to believe that ‘true hunger has returned’, and that they should break their fasts. Usually (but not always), this phenomenon simply constitutes a totally normal physiological phase of the fast, or – even more likely – their digestive juices are being driven by an increasing emotional desire to eat. Without someone offering an objective mirror on the outside, it can be extremely difficult to distinguish between the different possible scenarios!

In addition, two other less obvious scenarios demand the end of a fast. The first possibility is that you run out of amino acids (derived from muscle tissue) before you deplete your fat stores. In order to power your body as a whole, it’s true that ketosis is extremely efficient. The problem is that the brain demands another fuel entirely: glucose. And this cannot easily be metabolised from fat tissue. Instead, the body must extract it by breaking down proteins in a process called gluconeogenesis (described in greater detail in my article on the 3-day fast). However, the actual danger of depleting amino acids before fat tissue is largely theoretical. I have never witnessed this happen myself, and it is only likely to arise on fasts longer than 40 days in the case of someone who is morbidly obese with severely atrophied muscle tissue.

The final possibility is certainly a real danger: the depletion of electrolytes (blood salts), especially potassium or sodium. Although unlikely, this process is potentially life-threatening! Understandably, many people decide to take electrolytes while fasting, precisely in order to avoid this scenario. If the sole reason for fasting is to lose weight, then by all means do so! However, if you are fasting because of a chronic health issue, it is critically important to understand that taking electrolytes during a water fast compromises both the deepest cleansing and healing – as I have observed clinically among clients who choose to fast using electrolyte supplementation. (I will delve into the physiology of this in a future article.) Although the danger of electrolyte imbalance usually increases from only about the 21-day mark, it is extremely important to respond to the first warning signs if and when they do arise. Unfortunately, this is difficult to the untrained eye, because the symptoms of potassium and sodium depletion overlap with other totally normal detox symptoms. The key is in understanding the context as well as the overall, underlying symptom picture.

Refeeding:

After you break an extended fast, it’s extremely important to follow a well structured meal plan. In an ideal world, this should be tailor-made to the individual person, based on prior nutritional reserves, any dietary sensitivities, as well as the given health issue for which someone has fasted. When this is not possible, a comprehensive pdf on refeeding can be found in the webshop here:

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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353 responses to “14–40 Day Water Fasts: Healing Power, Benefits & Risks”

  1. Mallorie Nielsen Avatar
    Mallorie Nielsen

    Good morning,

    I’m looking to do a 40 day fast for Lent. During my bible reading I believe God put this in my heart. I am a little overweight. I’m 37 yo F, 5’8” 177lbs, carry a lot in my mid section so def not underweight to do it. I just want to make sure I do it safely and know I have some time to prepare my body mentally and physically. Right now I do 24 hours fast a couple times a week and have lost some weight. I would like this fast to be most importantly be more spiritual and if I get some health improvement from it as well I would love that.

    1. Hi Mallorie,
      Thanks for sharing. Yes, I’m sure you’ll get some physical health improvements along with the spiritual!
      Wishing you all the best for your fast,
      Tallis

  2. Hi Doc
    I have been recently diagnosed with hashimotos with adrenal insufficiency. I started on a thyroid supplement about 2 weeks ago but am really resisting being on the medications. Is fasting a good option or no. I will be consulting with you if your recommendation is to proceed. If not then I will stick with iodine supplement and the supplement for now pending further research

    1. Hi Susan,
      Thanks for writing. To answer your question: extended fasting is almost certainly your best option to achieve a long-term improvement and healing of your symptoms, and also without you having to be reliant on long-term medication. Generally, the actual improvement to blood levels of Hashimoto antibodies follows after symptomatic improvement through fasting. It’s hard to say anything more specific than this – along with going into what particular fasting protocol might be best for you – without a much deeper discussion with you about your case.

      If you’d like to set up a consultation, you can reach me via the coaching page:
      https://waterfasting.org/online-coaching-and-consultations-for-water-fasting/

      Hope this helps,
      Tallis

  3. I will be doing an extended fast. Are there any tests I can take before and after the fast to measure the benefits of the fast?

    1. Hi Jack,
      Thanks for writing. You can find tests to measure pretty much any metric you want, so it’s really up to you to decide what you’d like to look at. For instance, many people will measure A1C or CRP, because these are generally good overall markers of blood glucose metabolism and systemic inflammation, respectively. But if you don’t have a problem with either of these issues, you’re unlikely to see too much of a change.
      Hope this helps,
      Tallis

  4. Hello. I am looking to start a water fast, trying to go 30 days. Have you heard of people with IBS coming out of a long fast doing better? I have had it for a couple decades and never been able to find a way to get rid of it or even make it minutely better. Thanks for being awesome.

    1. Hi Brian,
      Thanks for writing. I work with many clients suffering from gut issues, who come out of their extended fast in a much better place than before – with many fully healed. In terms of what length and protocol is best, that tends to be quite individual – and this holds even more true for how you approach refeeding.
      Hope this helps,
      Tallis

  5. Hello Dr. Barker, I would like to book a consult with you as I prepare for a 30 day water fast for breast cancer. I am not looking to be supervised in daily check ins as I have community and my family doctor supporting me but I would like to have an ally with prolonged fasting experience to speak to a few times during the month (I’ve only done 5 days – but I have done a lot of research in this area). Do you offer that? And are you willing to work someone who is taking trace minerals and some electrolytes during the fast? It doesn’t sound like that is your approach but I feel that is best for my body. Other practitioners I have contacted will not share much information unless I join their program. So I am unsure of your consult approach. Thank you so much. Great website-so much valuable information!

    1. Dr. Tallis Barker, D.Phil., Nat.Dip. Avatar
      Dr. Tallis Barker, D.Phil., Nat.Dip.

      Hi Heather,

      Thanks for writing. I’m very happy to set up a consultation and work with you as you suggest. I do work with most of my clients on a daily level, but I understand that different people have different needs, and I try to be as flexible as possible to accommodate people’s individual situations.

      You’re right about the electrolytes and trace minerals: whenever possible I do discourage their use, because beyond any reasonable doubt they limit the maximum amount of detox and healing. So long as you’re aware of this and understand the implications, then I’m still happy to work with you. The flip side of this is that the most dangerous complication on a fast is potential electrolyte deficiency. If we’re not working together on a daily basis, then the use of electrolytes protects against this happening. (When working with daily clients on full coaching, this risk is mitigated by the fact that you have me looking out for the relevant symptoms, and so only very rarely is electrolyte supplementation necessary.)

      If you’d like to sign up for a consultation, you can reach me via the coaching page here:
      https://waterfasting.org/online-coaching-and-consultations-for-water-fasting/

      Looking forward to hearing from you soon,
      Tallis

  6. I can’t even make three days and feel healthy without electrolyte supplementation. With supplementation, I cruise right past that phase. I think my body requires it.

    1. Dr. Tallis Barker, D.Phil., Nat.Dip. Avatar
      Dr. Tallis Barker, D.Phil., Nat.Dip.

      Hi Mike,
      Thanks for writing. Water fasting is pretty much the strongest cleanse that exists, so low energy levels and detox symptoms are inevitable. Don’t give up – it will get easier! And then you’ll be free to enjoy the full healing power of a water fast without feeling the need to rely on supplementation.
      All the best,
      Tallis

  7. Leslie A Aul-Broz Avatar
    Leslie A Aul-Broz

    I completed a 21 day Water fast in March. My family put pressure on me to stop at day 21, even though I feel I could have gone longer. I am considered obese so I was not worried and researched based on my body fat how long I could safely fast. I want to start another 21 day fast, is it too soon? Also, I experienced many benefits, besides the weight loss, I no longer have toe nail fungus and two scars on my face have almost disappeared! Your site got me motivated for my first fast because I was actually only going to do a 7 day fast, but your encouragement to keep fasting helped me complete the 21 days. Thank you for any further guidance you can give me!

    1. Dr. Tallis Barker, D.Phil., Nat.Dip. Avatar
      Dr. Tallis Barker, D.Phil., Nat.Dip.

      Hi Leslie,
      Thanks for writing. That’s great you did a 21-day fast, experienced a lot of healing, and felt like you still had reserves. In terms of doing another 21-day fast, it’s likely that for someone like you it would be absolutely fine to start whenever you like – assuming that you eat a full, nutritious diet and don’t have a lot of gut issues which could negatively impact on nutrient absorption. Enjoy!
      Tallis

  8. Hello. Currently on day 6 of a water fast. I still make food for my family during this time. Will it disrupt the fast if I taste things that I’m making to check the seasoning, even if I am spitting it out and rinsing my mouth after?

    1. Dr. Tallis Barker, D.Phil., Nat.Dip. Avatar
      Dr. Tallis Barker, D.Phil., Nat.Dip.

      Hi Chris,
      Thanks for writing, and congratulations on your current fast! I often cook when fasting, but, within reason, I do try to avoid tasting when possible. It’s not going to massively disrupt your fast, but the tongue is an amazing antenna to the rest of your body. Taste on the tongue helps you prepare for the effect the food you eat is going to exert on your body. For example, even a sugar-free sweetener is capable of raising blood sugar, even though there are no calories in it! I know that sounds crazy – and there’s certainly no scientific explanation for it – but I’ve seen it happen clinically on several occasions.
      All the best,
      Tallis

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