Fasting (the abstinence of calories over a period of time) is an age old practice which plays a major role in many world religions and cultural customs across the world. It’s medicinal and spiritual benefits have long since been known about and observed and now 21st science is showing us the true magic(1) that happens when our bodies are given the chance to go into “Rest and Repair” mode.
Fasting was a normal part of the human life until the Neolithic/Agricultural Revolution, around 12,500 years ago - a blink of the eye in evolutionary terms. Anatomically modern humans have existed for roughly 200,000-300,000 years and for the vast majority this time, we roamed across the Earth, living the nomadic, hunter-gatherer lifestyle. We were highly mobile and active, moving with the seasons and eating the freshest, highest quality (organic) foods each season had to offer. However; “Unlike today, our ancestors typically had to compete among themselves and with other species for a limited supply of food. In this context a survival advantage was conferred on individuals that were quick-witted, physically agile, and energy-efficient during periods of limited resource availability.”(2) In other words, we biologically adapted to experience periods of deprivation of both food and water, in times of limited resources. Archaeological data shows that the hardships and tests of physical endurance of the previous climate changes and the Earth’s wild and unruly nature, put us through our paces. We acclimatised and thrived.
“If our ancestors couldn’t function when we were hungry, we wouldn’t be here”. - Peter Attia, Longevity Scientist
The transition to a more sedentary, agriculturalist lifestyle with it’s domestic produce-dependent and therefore less varied diet, combined with new and often unsanitary living conditions was sudden, and its negative impact on humanity profound. It’s impact on the environment was also devastating. Once populations had increased due to the over abundance of agriculturally-produced foods, man was trapped in a cycle, needing to produce ever more in order to feed the rapidly booming populations. Around this time, the Great Forgetting began; and with it a paradigm shift in mental attitudes; our understanding of our place in the world, our relationship to other animals and our environment, food and human mental and physical health. Prehistory is our history - it’s the human story. The westernised version of human history has been: “...reduced to the period exactly corresponding to the history of our culture, with the other ninety-nine point-seven percent of the human story discarded as a mere prelude.”(3) Thus our understanding of our history and context as a species on this planet has been severely distorted and limited, to the disservice of our understanding of ourselves and our environment.
“We have a lot to learn from hunter-gatherers about what constitutes a healthy lifestyle.”(4)
Numerous studies(5), (6), discuss agriculture and the consequential settlement into a stationary lifestyle and its impact on human disease, human biology and the decline in our overall health. They paint a picture of our pre-agricultural ancestors as having far better physical and mental health than the westernised people of today, which is unsurprising in many ways. Fasting and a healthier attitude towards, and relationship with food, played a key part in our well being for millennia. We are so much more than what we eat/absorb! The benefits of fasting are being revealed and the findings are revolutionary.
If you are as fascinated as we are about the dawn of civilisations and the influence they’ve had on the cultures, spirituality, our environments, psychology and philosophy of today, we highly recommend you watch historian and author Michael Wood’s 6 part documentary Legacy which can be found on YouTube. “What can the past teach us about the present?” In a sublime journey across the 6 major, earliest civilisations, Michael Wood delves into their philosophies to tell the story of their rise and fall. Each story reveals much about human nature, our shifting attitudes and parables which we can learn a lot from, especially today.
“The best of all medicines is resting and fasting.” - Benjamin Franklin
For the majority of our time on this planet, less food would have been readily available. We would have had intimate knowledge of which foods were accessible where, and at which times of the year, which kept our ancestors constantly on the move. Their lifestyles would have revolved around the seasons and specific location-dependent food sources. However - and it’s hard to imagine now, that even with their intimate knowledge, ingenuity and creativity, food would not have been available all the time. The mass mono-culture agricultural farming of today keeps the supermarkets on every street corner, restaurants, cafes and refrigerators at home overflowing with food, and we grew up being told myths such as that you should be eating “3 meals a day” and that “breakfast is the most important meal of the day.” These ideas stem back as recently as either the Medieval Period or the Industrial Revolution - depending on which source you read - and evolved around the new working patterns dictated by societal shifts and new inventions such as electric lighting (which lengthened working hours) and enforced by institutions(7), (8). Before this, attitudes towards food was far healthier. For example, in Roman society, having more than one meal a day was considered gluttonous(9). Previously, we would have shifted naturally between cycles of fasting and feeding and caloric restriction and would have eaten when hungry or when food was available, rather than when we were told we should.
“European(s)...changed the biological demands of eating and turned it into a forced food farce. Ignore the manmade routine and follow your own appetite for a healthier life.”(7)
“When an animal, such as a dog or cat, is sick, its natural instinct is to refuse food. When the crisis is over, and the internal healing work has been accomplished, the appetite will return naturally, of its own accord.“(10)
“The human organism also has a fasting instinct, just like that of other animals. Evolutionary adaptation has made our bodies very efficient at storing energy reserves, and drawing upon them when food supplies are scarce. Fasting is as old as mankind, perhaps even older.”(10)
Rest + Repair Mode in Human Biology
We are biologically adapted to experience these fasting and feeding cycles and when we halt caloric intake, our bodies naturally shift from the “Go-Go” mode into the “Rest and Repair” mode. Having an abundance of food available and eating too frequently does not allow your body the time it needs to rest and repair, and undertake processes essential for the maintenance and optimal functioning of our internal systems. Dr Michael Mosley discusses on his site The Fast 800, how 21st century western populations’ eating-habits have been attributed to diseases which did not exist until very recently, such as the increasingly common 80+ different types of autoimmune diseases. Lack of fasting, over-feeding, stress and the Hygiene Hypothesis are all modern phenomena which have been directly linked to poor physical wellbeing and mental health conditions.
“Natural forces within us are the true healers of disease.” - Hippocrates
The range of mental and physical benefits of fasting are vast so we’ve included only a few which we feel are most relevant below.
Put simply, water fasting is one of the safest and most powerful healing tools we have yet come across. It takes time to get fasting right - especially the re-feeding stage where it’s easy to make mistakes (see below). Once you are used to the fasted state and manage to fast regularly, the rewards are immense.
Read more about the benefits of fasting here.
Research has found that restricting caloric intake turns on genes which tell your cells to preserve their resources. While in the fasted state, cells go into a preservation or “famine mode,” where they are much more resistant to disease or cellular stress. They also enter a process known as autophagy(16) where the body begins to clean out the old, unwanted, and unneeded cells, as well as fixing and recycling damaged parts of the body. While autophagy is very difficult to measure outside of a lab environment, many experts agree that the autophagy process initiates in humans after 18-20 hours of water fasting, with maximal benefits occurring once the 48–72 hour mark has been reached.
“Fasting is the greatest remedy—the physician within.” - Paracelsus
The most powerful of all the fasting types is the dry fast - abstinence from liquids as well as solids, followed by water fasts - where you consume only clean, filtered water for a period of days or weeks. However, there are many different types of fasting and all have profound benefits. It’s best to try the top three fasting types we list below if you haven’t fasted before. You can then progress to water fasting which has even more benefits(17) and is an especially powerful healing tool for those with chronic gut disorders. It’s also one of the most powerful methods of reducing pathogenic bacterial populations, rebalancing the gut flora in favour of beneficial bacteria and promoting gut barrier/lining healing(15), which is also completely free!
***Remember to always consult a health professional and conduct your own thorough research before attempting any kind of fast - liquid, water etc. Each body and case is unique and individual and some fasting types may not be appropriate for you.
“We know from a variety of animal and human studies that what we eat, such as the relative amounts of fats, carbohydrates and proteins that we consume, can remodel the microbial communities living in our guts. But when we eat can also impact our gut microbiomes, and thus our metabolic health.”(15)
“Your gut is an ecosystem.” - Dr John Bergman
The gut is the largest and most dynamic immunological environment and organ within the body. “Indeed, gut-associated lymphoid tissue (GALT) is the prominent part of mucosal-associated lymphoid tissue (MALT) and represents almost 70% of the entire immune system; moreover, about 80% of plasma cells [mainly immunoglobulin A (IgA)-bearing cells] reside in GALT.”(18) Thus, 80% of the immune system resides in the gut, lending meaning to the saying “All disease begins in the gut”. 10% of your daily energy expenditure is required for the energy-intensive task of digestion alone(19). Considering these facts, it’s no surprise that by allowing your gut to rest, your body can switches into “Rest and Repair” mode where the energy and resources usually sapped by digestion, are reappropriated into restorative and rejuvenating processes such as autophagy, in turn, maintaining, detoxing and cleansing our internal systems. For those with a gut disorder, the best thing you can do is to allow your gut to rest. While in “Rest and Repair” mode your gut will also begin to heal itself (in numerous ways!) and even after a short water fast of 40-72 hours, you can notice a huge improvement in gut motility and digestion.
How Does the Gut Heal During Fast Periods?
“Fasting has many effects in the intestine, which include boosting regeneration as well as potential uses in any type of ailment that impinges on the intestine, such as infections or cancers."(20) - Ömer H. Yilmaz
More research needs to be undertaken on this however as the gut is still little understood and studied.
Fasting + the Gut Microbiome
“Cyclical changes in the gut microbiome from feeding/fasting rhythms contribute to the diversity of gut microflora and likely represent a mechanism by which the gut microbiome affects host metabolism.” — Zarrinpar et al. 2014
The gut microbiome - a vast ecosystem of organisms including bacteria, yeasts, fungi, viruses and protozoans - that reside in our digestive pipes, collectively weigh up to 2kg - more than the average human brain(24)! And these (100 trillion) microorganisms regulate our immune health(22) and much more besides.
Although microbiome studies and the science of fasting are relatively new, we know that fasting profoundly affects our microbiota populations and can “balance” our gut flora in favour of the good bacteria, or in other words it can: “increase gut bacteria richness”(25). And this makes sense; “Only recently have humans and domesticated animals had constant access to food. During their evolution, many animals and humans ate only intermittently. For many microorganisms and invertebrates, long periods of starvation are normal and, correspondingly, many of them (including C. elegans) have evolved forms of quiescence in response to the onset of food shortage.”(26) “...many species of ‘bad bacteria’ have a relatively short doubling time. So, if you fast, they will tend to starve more quickly than the healthy bacteria in your gut. Many of these ‘good bacteria’ have longer doubling times, and won’t be as greatly affected by your fasting…”(15)
More IF/TRF studies are currently underway in human trials and more prolonged water fasts in human trials have yet to be undertaken. However, we have both experienced this die-off/rebalancing effect first-hand while water fasting and have found it a powerful tool and not only in decreasing our bacterial burden, but also in promoting gut motility and healing (the underlying cause of SIBO being gut motility dysfunction which was triggered by years of chronic anxiety). Water and intermittent fasting is an integral part of our healing journey and we discuss how this practice has positively impacted our lives in more depth in the Our Stories section and a below.
The Fasting Cure
Likewise, there is much anecdotal evidence of the restorative powers of fasting from non-scientific sources which inspired us to begin experimenting initially, and made us wanted to experiment and experience the benefits for ourselves. One source was stumbled across was The Fasting Cure - a little known book which was a bestseller in its day - written by American writer, socialist and maverick Upton Sinclair. For years, Sinclair suffered from poor health and especially gut complaints - probably stress and lifestyle-induced - which no doctor could diagnose or medicine could remedy. Deciding to take his health into his own hands he became proactive, learning about and experimenting with diets, nutrition and fasting and his subsequent journey towards health changed his life entirely. The majority of the book (see link) is the article he wrote which was published in Cosmopolitan Magazine in 1910 (US) and in Contemporary Review in 1901 (London), which recounts his experience with ill health and fasting. Like Sinclair himself, it was way ahead of his time. The later published book also contains not only his story, but also numerous positive testimonials at the end from those who, upon reading his article, decided to undertake water fasts on their own, to cure themselves of various ailments.
The book describes how, after suffering with chronic ill health and particularly digestive issues for many years, he discovered fasting and began methodically experimenting with the practice himself. Astounded by the benefits and surprised at how few people knew about fasting and its ability to rejuvenate and restore health, he became an advocate. As amazing and inspiring as this source is however, it’s important to read multiple sources (especially the scientific sources which we reference above) and please note that his dietary recommendations were right for him and his particular case, and may not be right for you. His book is a brilliant insight into the healing powers of fasting however and we still highly recommend this to anyone interested in the practice. Despite the fact that this book is over 100 years old, it is highly relevant to the lives we live now.
“I have nothing to sell and no process patented. It is simply that for 10 years I have been studying the ill health of myself and the men and women around me. And I have found the cause and the remedy. I have not only found good health, but perfect health; I have found a new state of being a potentiality of life; a sense of lightness, cleanliness and joyfulness, such as I did not know could exist in the human body. “I like to meet you on the street,” a friend said the other day. “You walk as if it were such fun!””(27)
Microbes not only directly dominate and influence our appetites, they have also been shown to produce neurotransmitters! Thus, an overgrowth of microbes in the GI can corrupt the signalling pathways between our guts and brain, interfering with hunger and satiety hormones and impacting our eating behaviours and food choices. Microbes may also affect neuroplasticity, adding new understanding to how they shape our emotional eating behaviours(28).
Combating Emotional Eating
It is only while fasting that we realise the extent of our unhealthy relationships and attachments to food and certain foods above others. Fasting can allow us to gain a higher degree of control over hunger, satiety and emotional feeding behaviours and develop a greater level of emotional detachment and control.
Fasting is the perfect time to work on building healthier attitudes to foods, beverages and all that we usually consume and help conquer addictions such as sugar and caffeine. Meditation can not only help improve this relationship(29) but you may notice your meditation practice deepening, strengthening and going to a whole new level while fasting.Meditating while fasting helps reduce cortisol levels which naturally increase while in the fasted state, enabling deep relaxation and increased mental stability, awareness (especially of cravings) and enhanced levels of clarity and mental control.
“Time is an illusion. Lunchtime doubly so.” - Douglas Adams
While fasting, its common to experience a feeling of being lost and empty - as though there is a huge hole in your life which is usually filled with thinking of food, planning meals and eating and drinking. Indeed, once we stop food and drink consumption (except water and some herbal teas) we realise just how much of our time is eaten up by just thinking about food, planning meals and grocery shopping! While fasting, time slows down and we suddenly have more time than we know what to do with. We can spend our time differently and work on self-development such as strengthening our levels of self-control and self-awareness etc. We use this special time - almost gained time - to do all the things we normally don’t have time for. We chat more about this phenomenon below.
"Instead of using medicine, rather, fast a day." - Plutarch
Practicing IF/time restricted feeding - especially for extended periods of time - has profound positive benefits and we have an in depth knowledge of exactly how it impacts our health (more than we know about water fasts), as thorough research has been conducted on this topic. We’ve included multiple links to articles and studies on the many benefits which arise from being in the “fasted state” above, but this video by Thomas Delauer is a great introduction to IF, explaining how the practice can promote gut health.
The most popular IF/TRF schedules are as follows -
Preparing for a fast and how you will break the fast can be the make or break. The key to a successful fast is planning and listening to your body. If the detox and/or die-off symptoms are too intense, it might be time to break it and try again. Remember that any amount of fasting is good and don’t feel guilty or negative if you break fast sooner than intended. You can always try again. Before you start, write a list of intentions - why are you doing the fast? How many days are you aiming for? This will help remind you why you are fasting, help you stay on track, motivate you and help you through any tough patches. They always pass and it’s important to remember that fact and to just keep on going! Or as Dory from ‘Finding Nemo’ says - “Just keep swimming.”
The 3-5th days can be the roughest as your body goes through a huge shift, transitioning from one energy source (glucose) to another (ketones) while spring cleaning/detoxing each internal system. These first few days are the hardest and it’s normal to experience some discomfort such as feeling cold, fatigued or flu-like symptoms. You will want to make yourself as comfortable as possible. We find doing the below lifts our mood during these times -
Knowing what you can safely drink (that isn’t just filtered water!) while fasting and between meals so that you aren’t kicked out of autophagy can be tough. Most non-caffeine herbal teas are safe but not all are SIBO-friendly. Here some which are fasting and SIBO-friendly. Remember to only have max 3 a day. You will want to drink mostly clean water throughout the maximise the benefits of the fast -
Fasting for Medicine + Purification in Ancient Greece
“Spiritually, fasting helps us transcend our addiction and attachment to food, and to realize that man doesn't live by bread alone. The mind gets clearer, and spiritual awareness deepens. Freed from having to satisfy physical hunger, one can then turn one's attention to feeding the mind and spirit. Spiritual masters like Pythagoras wouldn't admit any disciple into their higher teachings unless they had first purified themselves through fasting.”(31)
Food = Comfort + Safety
While undertaking an 11 days fast, Jeanette Winterson discovered that “...the very thought of not eating makes people anxious. Food is comfort. Food is safety. Food is plenty.” In this Guardian article, she reflects that what sets us apart from the rest of the animal kingdom is our sense that we are more than just our bodies; we are more than reproduction, what we eat and mere survival. We are spiritual, creative and curious beings which search for meanings beyond what we see. When we fast, we can connect more deeply with these other aspects of being human - the aspects beyond food. It’s hard to explain this freedom from food and the routine of meals in words to those who haven’t experienced this sense of liberation before, however, the quote above does a great job. Upton Sinclair described it brilliantly too, when he wrote; “I have found a new state of being a potentiality of life; a sense of lightness, cleanliness and joyfulness, such as I did not know could exist in the human body.”
“Why are you Starving Yourself?”
Revealingly, Winterson notes; “When I decided to embark on an 11‑day fast, my friends decided I had gone crazy. Eleven days with no food? Why would anybody want to do that?” This is an attitude we are all to familiar with. ‘Won’t you die after a day without food?’ ‘Why are you choosing to starve yourself?’ etc. The best things to do to combat these unhealthy and uninformed attitudes is to become knowledgeable and informed in the science of fasting, and to write your intentions down so you know exactly why you are undertaking a fast and what you hope to achieve during and after. Listing your reasons for fasting serves as a great reminder and motivation throughout the fast.
Fasting - When Time Slows Down
“...as Leonard Cohen put it – humans are always looking for things to do between meals.”(9)
When our time is freed up from shopping, thinking about food, planning meals, cooking and eating, we suddenly realise not only how time-consuming eating is but also how much it governs our thoughts, actions, daily routines and rules our lives in general. Fasting in this respect can be immensely liberating and the freedom exhilarating.
“Fasting can be one of the most powerful health interventions at your disposal but it’s only worth it if you break the fast properly.”(32)
Refeeding is just as - if not more! - important than the actual water fast itself. This is the final part of the fast and much of the magic and benefits from the actual fast begin during this phase, as we start to build up our bodies again. However, the benefits can all too easily be undone if we overeat or eat the wrong foods. Your body is super vulnerable after a fast and eating the wrong thing or too much too soon, can result in a huge amount of damage and a destroyed digestive system which can last for months(33)! Or until after your next fast(s). It’s so hard to get this part right and avoid undoing all the hard work and to not miss out on the benefits as a result. The worst thing you could do would be to start eating foods which are hard to digest, that cause inflammation or gastrointestinal stress. To avoid this heartbreak and disappointment, we give some advice below which we discovered after making many, many mistakes ourselves!
Safely Breaking Fast
“Every fool can fast. Only a wise man knows how to break a fast.“ - George Bernard Shaw(32)
There is a lot of conflicting information out there about how to break fast - such as with fruit juice or fruit or fermented foods - which are not gut dysbiosis and autoimmune friendly. Our recommendations on how to break a fast - which we still follow religiously - are below -
The rule for water fasting and refeeding -
number of days you water fasted for X 3 (times by 3) = number of days you should refeed
While refeeding between long water fasts of 7+ days, it is safe to undertake short water fasts of 72 hours and less but remember that this is your time to build up your body and strength so be sensible about how many short fasts you undertake during this time - once a week is fine. After gently breaking fast and refeeding for a few days, you can start up your favourite IF routine again and to concentrate on building up your body and your reserves (with good fats), stocking up on vitamins, minerals and refuelling with nutrient-rich, dysbiosis, gut and AI-friendly foods.
Breaking a Water Fast + Refeeding
Breaking a Dry Fast