Water Fast Coaching and Nutritional Therapy

Introduction:

Why in the world would anyone want to fast for weeks and weeks?
It’s a perfectly reasonable question. And after more than a decade of working closely with over 1,000 clients through water fasts and the subsequent refeeding process, I can tell you that there’s no simple answer. For some people, extended fasting is primarily a spiritual journey. For others, it’s an attempt to address longstanding health problems after years of struggling to find an effective solution. And for many, the physical, emotional and spiritual motivations are inseparable.

Over the years, I’ve witnessed some remarkable changes in clients undertaking extended water fasts, including people who have reported substantial improvements in chronic symptoms — and sometimes their complete resolution. I’ve also sometimes seen disappointing results, unexpected complications and situations in which continuing a fast would have been entirely inappropriate.

What I want to make clear from the outset is that a longer fast is not necessarily a better fast. Nor is it necessarily a more effective one.

Nevertheless, I believe that extended water fasting deserves serious attention. Beyond the fact that the metabolic changes which accompany the prolonged deprivation of food are fascinating in their own right, the outcomes I’ve encountered in my own practice remain difficult to explain fully through the scientific research currently available.

So what actually happens during a 14, 21, 30 or even 40-day water fast? How might the experience differ from shorter fasts? What are the potential benefits, and where do the risks begin to outweigh them? These are the questions I’d like to explore in this article.

I’d like to begin by stressing two essential points:

• First, very little scientific research has been conducted on water fasts lasting several weeks, particularly beyond 20 days. Much of what follows is therefore based on my own professional observations. These observations may be valuable, but they should not be confused with the findings of controlled clinical trials.
• Second, prolonged water fasting can be dangerous and, in extreme circumstances, life-threatening. Medical assessment and appropriate supervision are essential considerations, especially for people with chronic illness or those taking prescription medication. In some situations, an extended fast should not be attempted at all.

This article is therefore intended to provide information the subject, not to provide a protocol for undertaking an extended fast independently.

About the author: Dr Tallis Barker, D.Phil., NT.Dip., Nat.Dip., is a naturopathic water fasting consultant and nutritional therapist who has worked with over 1,000 clients internationally. His work includes individual fasting consultations, nutritional therapy and published case reports. His D.Phil. is an academic doctorate, not a medical qualification. Full bio here.

Physical, emotional, spiritual healing:

The first thing I’d like to say is that — like it or not — a 14, 21, 30 or 40-day fast is potentially much more than just a physical experience. It can and, I believe, should touch you on deeper levels of being too.

Nowadays, most public discussion of fasting revolves around weight loss, ketosis, insulin, autophagy and other physiological processes. These are all valid subjects, and they certainly deserve attention. But historically, fasting also occupied an important place in spiritual life.

In my experience, it is pointless — and often unproductive — to try to fully disentangle the physical aspects of ourselves from the emotional, psychological or spiritual elements. I personally believe that these different levels of being are deeply intertwined. This isn’t simply an abstract philosophical position: it’s something I encounter time and again when working closely with people through extended fasts.

For some clients, fasting becomes an unexpectedly profound emotional experience. Old fears may emerge. Questions about identity, relationships and the direction of one’s life can suddenly become impossible to ignore. Long-buried feelings sometimes rise to the surface, particularly when the familiar distractions and comforts of everyday life are temporarily removed.

I often describe this as a kind of emotional detox. This doesn’t necessarily mean that emotions are biochemical toxins which need to be expelled from the body. Rather, fasting can facilitate a perspective in which people encounter aspects of themselves that they’ve been avoiding for years.

Some experience what they describe as a release of trauma. Others speak of an extraordinary quietness, or a sense of inner calm. One client once told me that, after a profoundly intense period during his fast, he felt he could literally take a deep breath for the first time in years.

Of course, none of this means that emotional surrender can cure physical illness, or that people who don’t improve simply haven’t opened themselves sufficiently to the process. Illness and health are far more complex than that. Nevertheless, I would argue that reducing extended fasting to a purely metabolic intervention risks overlooking a significant part of the human experience.

Benefits and risks of extended water fasts:

When considering a fast of 14, 21, 30 or 40 days, it is important to understand why you’re aiming for the given length of fast. Some people assume that if a 7-day fast is beneficial, a 21-day fast must be three times better. Unfortunately, physiology isn’t that reductive! Longer fasts mean you do spend more time in a distinctive metabolic state, but also more time exposed to nutritional depletion, changes in fluid and electrolyte balance, the psychological demands of food deprivation and other challenges.

The balance between potential benefits and risks varies enormously between individuals.

Over the years, I’ve received numerous emergency phone calls from people who began fasting alone, followed an inappropriate protocol or continued despite developing serious problems – with some of them ending up in the ER as a result. These unfortunate incidents have reinforced my conviction that undertaking an extended fast should never be treated casually.

When considering the suitability of an extended fast, I find that several important factors come into play:

• The overall health picture. Someone may approach me because of one particular condition — perhaps longstanding digestive problems, chronic fatigue or Long Covid. However, a deeper look at their medical history often reveals other difficulties, medications or nutritional considerations which burden their health, and which must also be taken into consideration.
• Physiological vulnerability. Age, body composition, nutritional status, existing illness, kidney and cardiovascular health and medication use can all influence risk. The immune system lacks any single measurable ‘strength’, and feeling generally fit is not a reliable substitute for a deeper health assessment.
• Previous experience. People who have fasted before may be more familiar with some of the sensations and psychological demands involved. However, familiarity does not necessarily protect them from complications on later fasts, and previous success doesn’t guarantee future safety.
• The ability to rest and recover. Extended fasts place substantial demands on the body. Continuing a physically or emotionally exhausting lifestyle throughout such a fast can add further stress – and in some cases can be dangerous.

With all these issues in mind, let’s take a look at some individual fasting durations.

Medical information: This article is educational and does not constitute individual medical advice. Extended water fasting involves potentially serious health risks and is not a substitute for appropriate medical treatment.

14-day fasts:

In my article on 7–10 day water fasts, I describe the first week as something of a ‘spring clean’. During the first several days, the body undergoes significant adaptations to food deprivation, including depletion of glycogen stores, increased mobilisation of fat, and greater reliance on fatty acids and ketone bodies for energy. Many of these adaptations become firmly established by the end of the first week of fasting.

Going into the second week of fasting, the experience may begin to change. Some clients report that the initial headaches, nausea or general discomfort which may have presented during the first week diminish, while fasting symptoms more associated with their specific longstanding health conditions become more noticeable. Others experience a completely different progression.

Among the people who approach me for 14-day fasts are those living with digestive conditions such as IBS, inflammatory bowel disease (IBD), ulcerative colitis and suspected disturbances of gut permeability (‘leaky gut’), as well as people with eczema or psoriasis.

I have worked with clients who report encouraging improvements in some of these symptoms, although of course this is not a universal response. (Nor does the fact that an improved symptom establish that the underlying disease has been cured.) It is also important to understand that not every fasting symptom automatically constitutes a stage of the healing process. Headaches, nausea, weakness and dizziness can have several possible explanations – including potentially serious complications.

Potential risks of a 14-day fast:

The assessment of possible nutritional deficiency prior to the fast should be a significant consideration before undertaking any extended fast. In the modern world, this often means more than simply a lack of sufficient food. In my experience, it can also mean (1) an unhealthy diet high in processed foods which lacks full nutrition, (2) any diet which is overly restrictive in the food groups it involves, or (3) nutritional insufficiency caused by longstanding absorption and gut issues (eg SIBO). Any of these issues can lead to problems involving hydration, blood pressure, blood sugar and electrolytes both during as well as after the fast.

For any fast of 14 days or longer the refeeding period also deserves particular attention. Not only does this help to ensure digestive comfort. It also minimises the possibility of refeeding syndrome: a condition which involves potentially dangerous changes in electrolytes and fluid balance. This is especially important for those with already compromised nutritional health, and who are thus more vulnerable to the development of refeeding syndrome in the first place.

For all these reasons, a 14-day fast should never be regarded as an uncomplicated extension of a shorter fast.

Continued below:

21-day fasts:

The shift from 14 to 21 days may not sound particularly dramatic — after all, it’s just an additional week. But for many of my clients, that extra week feels disproportionately hard. Psychologically, three weeks can begin to feel much closer to a month than to a ‘mere’ two weeks. And physically, the cumulative demands of fasting become increasingly important.

I have worked with clients considering 21-day fasts who have presented with a wide range of longstanding health concerns, including:

• Metabolic and hormonal conditions such as high blood pressure, metabolic syndrome, insulin resistance, type 2 diabetes (T2D), thyroid disorders, PCOS and other gynaecological problems.

• Inflammatory and autoimmune conditions such as rheumatoid arthritis (RA), asthma, allergies and other chronic inflammatory symptoms.

• Complex longstanding conditions such as chronic fatigue (CFS/ME), Long Covid, Lyme disease and other persistent health complaints.

Of course, this is not a list of illnesses that a 21-day fast has been proven to treat, and no scientific evidence suggests that 21 days represents a universal therapeutic threshold. It is simply a description of some of the people who have sought my guidance. In short, I’ve worked with numerous clients who report meaningful improvements in their particular symptoms, alongside others who have experienced more disappointing results or whose medical circumstances made continued fasting unsuitable.

Potential risks of a 21-day fast:

Three areas have stood out in my own practice:

• Electrolyte disturbances:
  Electrolyte imbalance is one of the most important medical concerns during any extended fast. Sodium and potassium disturbances, in particular, can have serious consequences, including cardiac and neurological complications. In my own work, I have encountered comparatively few apparent electrolyte problems during shorter fasts, but they can and do arise during longer ones – and knowing how to intervene is crucial in order to maximise safety and comfort. Certain health concerns also increase the likelihood of electrolyte imbalance developing in the first place. In some cases, this may mean it is best to curtail the length of a fast or even avoid extended fasting altogether.

• Hormonal changes:
  The endocrine system responds to prolonged energy deprivation, and these responses can differ substantially between individuals. Changes in thyroid function, stress hormones (adrenal function), reproductive hormone signalling and other endocrine pathways are among the recognised physiological adaptations to fasting. This may explain why some clients report a change in their hormonal blood panels before and after an extended fast.
  
  Clinically, I’ve also observed changes in menstrual patterns among numerous women following an extended fast. Some women report long-term improvements in cycle regularity over the subsequent months, especially when they have been able to rest adequately during their fast. Others experience disruption, especially in the immediate aftermath of a fast, and especially when they have unduly exerted themselves during their fast.
  
  In this sense, it is extremely important to consider the impact of rest versus stress on the endocrine system during an extended fast. For just as I believe a hormonal ‘recalibration’ may be possible, so a hormonal ‘dysregulation’ may also result.
  

• Psychological challenges:
  The psychological dimension of extended fasting has already been mentioned, but by three weeks the experience can become particularly demanding. For some people, this is where the emotional journey becomes more intense, and it can become tempting to push through the challenges at whatever price. However, there is a difference between finding something challenging and finding it psychologically overwhelming. It is hugely important to understand and respect that distinction!

28-30 day fasts:

28 or 30 days is essentially a whole month, and this constitutes an exceptionally long period without food! Over the years, some of my clients have felt that the additional time helped consolidate improvements. That is their experience, and I believe it needs to be heard. However, it is equally important to add that no robust scientific evidence affirms that physiological benefits become permanently ‘locked in’ after a particular number of fasting days.

Among the people who approach me for 28-30 day fasts are those living with hormonal imbalance/dysregulation, autoimmune and inflammatory issues, Long Covid, peripheral nervous system (PNS) issues such as peripheral neuropathy, and complex digestive issues including SIBO.

Peer-reviewed articles

Long Covid and SIBO (small intestinal bacterial overgrowth) have been areas of particular interest in my work, and in 2025 I published two peer-reviewed case reports covering 28-day fasts.

One article documents the resolution of SIBO in a client who underwent a 28-day extended fasting protocol. Entitled ‘The full healing of SIBO (gut dysbiosis) achieved through an extended water fast: a case report’, this paper appeared in the Journal of Preventive Medicine and Holistic Health.[1]

The other article documents the first recorded case of a full resolution of Long Covid in another client who underwent a 28-day extended fasting protocol. Entitled ‘A Full and Permanent Resolution of Long COVID Symptoms achieved through an Extended Hybrid Water Fast: a Case Report’, this paper appeared in the Journal of Traditional Medicine & Clinical Naturopathy.[2]

In both cases, the important takeaway is not that extended fasting universally cures SIBO or Long Covid, but rather that a specific 28-day fast yielded an individual outcome which deserves further investigation. (In this sense, a case report does not carry the same weight as a clinical trial.)

Potential risks of a 28–30 day fast:

Above and beyond the issues already covered in the section on 21-day fasts, the following concerns become especially prominent:

• Chronic nausea:
  I have observed chronic nausea to be one of the most difficult problems that can arise during very long fasts. Approximately one third of the clients I’ve accompanied through 28–30-day fasts have encountered significant nausea, although this is an estimate from my own practice, not a published incidence rate. When left untreated, the symptoms may intensify over several days, becoming increasingly difficult to tolerate. In such cases, even when blood tests come back normal, this does not necessarily establish that persistent nausea is harmless. Severe or worsening symptoms do require appropriate medical assessment, and it may be unsafe to continue the fast.

• Electrolyte and fluid imbalance:
  The longer a fast continues, the greater the concern regarding potential disturbances to fluid and electrolyte regulation. Hot weather, vomiting, excessive water intake, underlying illness, medication and the use of enemas can all complicate the picture. These problems cannot always reliably be diagnosed through symptoms alone, and this makes the availability of clinical monitoring increasingly important.
  

• Low energy levels:
  In my experience, many clients feel a substantial reduction in energy during the final week of a month-long fast. This matters not only physically but also because of the psychological implications. What initially felt like a manageable undertaking can begin to feel interminable – which, in turn, can can become a considerable source of stress. Beyond a certain point, this can then have a negative impact on the ability to control cravings during refeeding.

40-day fasts:

For millennia, 40-day fasts have occupied a special place. The great spiritual figures of the past didn’t choose to fast for 21 days. Or 30 days. No. It was always 40 days. Why? We may never know the answer. In asking potential clients to more fully consider the weight of a 40-day fast, I sometimes tell them that it is designed to break you. Buddha’s 40-day fast broke him. Jesus was taken to his own limits…

I do think this is an important consideration – and one which unfortunately some fasting retreat centres and water fasting experts largely ignore. I’ve certainly seen some of my own clients taken to their limits, both physically and psychologically. In my view, awareness of this issue is essential and not something to take lightly, because underestimating the intensity of the journey can have serious consequences. Because going to the limit is not for everyone.

Who considers a 40-day fast?

Some of the people who have approached me about exceptionally long fasts have been living with extremely serious illnesses, including cancer and central nervous system (CNS) conditions such as multiple sclerosis. These also frequently constitute the health concerns where the greatest caution is required. For the sake of clarity, it is also important to add that extended water fasting is not an established treatment for cancer, multiple sclerosis or other serious diseases.

Some potential clients hoping to do a 40-day fast are desperate for improvement, and it is precisely that desperation which drives them towards such an extreme intervention in the first place. Often, though, desperation can make fasting especially dangerous in terms of nutritional vulnerability, medication, ongoing treatment and the possibility of further physical deterioration. Although in some cases a 40-day fast may indeed make sense, I have equally had to advise potential clients against the extended fast they originally hoped to undertake, instead helping them to devise a protocol which exerted less of a potential burden on their health.

Potential risks of a 40-day fast:

Above and beyond the issues already covered in the section on 28-30-day fasts, the following concerns become especially prominent:

• An apparent law of diminishing returns:
  For certain health issues (eg digestive concerns), I have observed that 40-day fasts don’t necessarily offer a significant advantage over changes experienced earlier. Beyond a certain point, the additional risks may actually increase considerably while the hoped-for advantages remain uncertain.

• Chronic nausea:
  Over the years, approximately half of the clients I’ve accompanied through 40-day fasts have reported problems with chronic nausea. Of course, this estimate is based on my own professional practice rather than a finding from a formal research study. Without expert knowledge regarding appropriate treatment of the individual case, the severity of nausea also tends to be considerably worse than on shorter fasts.

• Electrolyte depletion:
  By definition, the longer the fast, the greater the risk of electrolyte disturbances, and it is one important reason that I choose not to coach fasts longer than 40 days. Of course, this is not to infer that fasts up to 40 days are inherently safe. Rather, any extended fast should be established on an individual, case by case basis.

• Psychological challenges:
  Instead of making a broad generalisation here, I’d like to share a specific experience that has stayed with me for several reasons:
  
  A few years ago, I worked with a woman who was living with triple-negative breast cancer. In her particular case, she reported that her tumour had become visibly smaller by the end of a 40-day fast, with an estimated reduction of approximately 50% in volume. I do realise how remarkable that sounds. Clearly, this does not prove that fasting treats cancer, just as an extended fast cannot substitute for oncology treatment. And clearly, an individual observation cannot establish that fasting was responsible for a reduction in tumour size. However, just because it may be difficult to interpret, I don’t believe that an observation like this should automatically be excluded from discussion.
  
  Rather, the point here is the impact this outcome had on my client. Following her first fast, she originally planned to undertake a second extended fast approximately six months later, hoping to build on what she believed had been a positive experience. When the time came, however, she simply couldn’t summon the psychological strength to face another extended fast.
  
  This was striking. Whatever interpretation one places on the physical changes reported in her case, the experience had clearly demanded a great deal from her emotionally and psychologically. To use a couple of my own terms introduced earlier in this article, she had experienced a lot of unexpected ‘emotional detox’ during her fast, and ultimately the extreme length of it had ‘broken’ her – or at least ‘burnt her out’ – in the sense that, contrary to her original plan, she felt should could not undertake a second fast.
  
  This risk of emotional and psychological burn-out is especially important when someone is already coping with a serious illness.

Please feel free to share your thoughts or questions in comments section below!

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[1] Barker T. The full healing of SIBO (gut dysbiosis) achieved through an extended water fast: A case report [Internet]. J Prev Med Holist Health. 2025 [cited 2026 Oct 22];11(2):99-101. Available from: https://doi.org/10.18231/j.jpmhh.14256.1764132626

[2] Barker T (2025) A Full and Permanent Resolution of Long COVID Symptoms achieved through an Extended Hybrid Water Fast: a Case Report. J Tradit Med Clin Natur, 14: 525. DOI: 10.4172/2573-4555.1000525

[3] https://www.nice.org.uk/guidance/cg32/resources/nutrition-support-for-adults-oral-nutrition-support-enteral-tube-feeding-and-parenteral-nutrition-pdf-975383198917

Further references:

Ezpeleta M, Cienfuegos S, Lin S, et al. Efficacy and safety of prolonged water fasting: a narrative review of human trials. Nutrition Reviews. 2024;82(5):664–675. https://doi.org/10.1093/nutrit/nuad081

Gustafson C. Alan Goldhamer, DC: Water Fasting — The Clinical Effectiveness of Rebooting Your Body. Integrative Medicine. 2014;13(3):52–57. https://pmc.ncbi.nlm.nih.gov/articles/PMC4684131/

Cancer Research UK. Alternative cancer diets. https://www.cancerresearchuk.org/about-cancer/treatment/complementary-alternative-therapies/alternative-cancer-diets

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