Cleansing and detox: how water fasting works and why it benefits you


  • Why water fasting offers the deepest detox?
    • The first level of cleansing: a rest from digestion
    • The second level of cleansing: ketosis
  • The time to fast and cleanse is now!

Why water fasting offers the deepest detox

There are countless diets, techniques and fads designed to help you detox. Many of these can certainly help, but if you’re really serious about cleansing, the most powerful method is and always has been water fasting (as well as dry fasting).

Why? Because only through sustaining a zero caloric intake can you fully unlock the body’s healing metabolism. This takes place in two steps.

The first level of cleansing: a rest from digestion

The first level of cleansing begins after your body has finished digesting its last meal. In this respect, what you eat impacts considerably. While most fruit and vegetables require only an hour or two to digest, meat takes much, much longer – even a day or two. Clearly, this is reflected in the amount of energy required for digestion, with the average diet accounting for a quarter to a third of the day’s total energy needs. So, for example, if you eat 2000 calories per day, about 600 calories of this goes simply towards digesting your food. When you stop eating, though, the energy normally used for digestion is freed up, and your body applies this to cleansing instead. That’s a lot of energy!

Taking a rest from digestion also conveys another benefit, by unleashing the full strength of your immune system. In everyday life, approximately 70-80% of the cells comprising the body’s entire immune system reside in the gut wall. This may seem surprising, but there’s a good reason for this. Every single time you eat, you also ingest potentially harmful pathogens which are liable to be absorbed through the gut wall, along with nutrients, into the blood. By leaving your digestive system in peace through a water fast, however, you free up this vast army of defense cells which are otherwise tied down your whole life. Instead of chasing down foreign invaders in the gut, cells from your immune system can now spread through the entire body to do their job. This can happen only through water fasting. Clearly, no juice fast or other cleanse which involves eating allows the possibility of such a systematic detox.

The second level of cleansing: ketosis

The second and much deeper level of cleansing begins once your body has entered the fat-burning metabolism called ketosis. This occurs only once your glycogen stores are depleted after approximately the first 24 hours of fasting (described in greater detail in the articles about one-day water fasts and three-day water fasts). The reason that ketosis is so important for cleansing is that many toxins are normally immobilised and stored in adipose tissue (fat cells), where they can’t interact with the body, causing damage. The beauty of fasting is that ketosis releases these toxins at a time when the immune system is already hugely strengthened (see above), and is thus able to safely excrete them once and for all from your body.

In everyday life, toxins accumulate because your immune system is tied down in the gut, and your kidneys and liver are already busy removing the toxic byproducts of digestion. The best your body can do is round up other toxins and pack them away in a safe place, saving their removal for a ‘rainy day’. If you don’t ever fast, though, your fat cells will eventually fill up with toxic junk. From this point onwards (usually sometime in middle age), toxins have no safe place to go. Instead they begin to circulate freely through the body, causing damage and eventually illness. This is arguably one of the reasons why, in the vast majority of cases, chronic disease is associated with middle and old age.

This whole process also explains why people on ketogenic (low-carb) diets falsely believe that their diet is cleansing. Given the prevailing but unfortunately overly simplistic view, it’s easy to equate any and all ketosis with cleansing. But given that the immune system is tied down in the gut, given that the kidneys and liver are fully occupied removing the toxic byproducts of digestion, given that most ketogenic diets require a large amount of energy for digestion in the first place, deeper detox simply cannot happen. Even beyond this, the ketosis fired by low-carb diets tends to involve only a fraction of the body’s total adipose tissue. That is, the same fat cells are used over and over again like a fuel tank, depleted and then replenished with fuel from the next meal. This means that most adipose tissue in the body is left untouched by the ketosis of low-carb diets, with no possibility for being cleansed in the first place. This is borne out by recent research which associates most low-carb diets with higher mortality rates than average. One study published in the Lancet (2018), for instance, concluded that non-vegan ketogenic diets could reduce lifespan by up to four years.

Check out the webshop on

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

The time to fast and cleanse is now!

Unless you happen to live far from human civilisation, the air you breathe is full of carcinogens. Unless you drink water fresh from a mountain spring, the liquid which constitutes 70% of your body weight is full of chlorine, the recycled hormones from contraceptive pills, not to mention a plethora of industrial waste products. Unless you eat fully organic food, your food is contaminated with pesticides, fungicides and fertilisers. If you eat meat and dairy products, you can also count on ingesting large quantities antibiotics and artificial growth hormone. Unless you fully avoid Western medical drugs, you can add the bitter pill of allopathic medicine, along with the toxic residues it leaves behind in the body. For ultimately, every drug is a poison – this is why overdosing can kill you. Let’s face it, mankind has poisoned himself along with the planet. Do you really believe you can escape this?

The fact is, we are all filled with filth.

Does this shock you? I hope so! Like it or not, you are going to need to detox at some point in your life. It’s just a question of when. The fact is that the human body is incredibly resilient, and it usually takes half a lifetime for your fat cells to fill with toxins to the point of saturation. But then, like a boat taking on water, there does come a tipping point. The boat begins to sink. Like most people, you can ignore the situation and wait until illness strikes. At this point, it’s often too late. Or you can begin now.

When I was young, the thought of cleansing didn’t even cross my mind. To me, it was something that neurotic health maniacs did. Then I tried out water fasting and, to my shock, witnessed the filth leaving my body. My breath stank. My sweat stank. My urine stank. My tongue turned a pasty white and began to literally froth, producing a bitter, metallic taste in my mouth lasting for days. It was utterly foul. And because it was so foul, I realised how good it was to free myself from all these toxins.

From that point on, I began to honour my body with fasting. With experience, I grew more attuned to my body’s inner needs. You will too. Your body will begin to speak to you, and you’ll feel an inner urge when it’s time to fast. It isn’t something you have to force on yourself. It isn’t something you need to plan out in advance on a calendar.  You’ll know when it’s time. Increasingly, you’ll look forward to that time.

Your body will love you for it.
And in return you’ll love your body back.

Unfortunately, it’s all too easy to sit on the fence – knowing and feeling that you should fast, and yet not quite reaching the point of actual commitment. It might be anxiety about hunger and detox symptoms. It might be your work schedule. Who knows. We all have our reasons, and it’s easy to find an excuse. If you need help in making that final step towards a water fast, I’m here to support you as a water fasting coach.

If you enjoyed this article, please share on social media, using one of the buttons below:

45 responses to “Cleansing and detox: how water fasting works and why it benefits you”

  1. Does loose leaf herbal tea sugar free impact a water fast?

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

      Hi Julie,
      Thanks for writing. Everything is going to have some kind of impact on a water-only fast. You certainly wouldn’t want to take anything beyond water on a primarily spiritual fast, since the whole point is to remove external stimulation. If your primary aim is physical healing, non-caffeinated herbal teas can certainly play a role. When working with clients I often suggest a particular herb in order to deal with certain detox symptoms, so their medicinal value is worth keeping in mind.
      All the best,

  2. Hi! Great article! I’ve been experimenting with various water fasts between 1-3 days, but tend to struggle with toxicity symptoms at the 72-hour mark and have to stop. One thing that continues to confuse me regarding long-term water fasts (20-40 days) is, if certain nutrients are essential for Phase 1 & 2 liver detoxification to take place (e.g. B vitamins and amino acids) and some of these can only be obtained through the diet, how does detoxification continue when consuming zero nutrients on a prolonged water fast? I can find lots of information on water fasting and plenty on detoxification, but can’t find anything on detoxification during fasting! If you have any thoughts/info on this, I’d be most interested šŸ™‚ Thanks!!

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

      Hi Donna,
      Thanks for your question: it’s one which makes an awful lot of sense! First of all, detox does clearly continue on 20-40 day fasts – in fact it only goes deeper the longer you go! In terms of Phase 1+2 liver detox, the nutrients/enzymes involved can largely be recycled by the body, as they facilitate the biochemical reactions taking place. So it’s not like you’re just dumping them out of the body. Also, the liver retains additional nutritive stores for everything it needs to maintain function, so it’s usually well prepared for something even as extreme as a 40-day fast.
      Hope this helps,

  3. Greetings, Tallis! I recently learned about the body making stem cells during a 72+ hour fast. I did a 42 hour fast a couple of weeks ago, and am currently at hour 54 this time going for 92. My question is, have you had any experience with muscle regeneration with the stem cell production? If-so, how long should I push it for & how often (depending on cycle days)? Iā€™m trying to avoid surgery on my torn rotator cuff. PRP injections did nothing. Praying this extended water fasting might do the trick as stem cell injection$ are wild ($$$$). Thank you for your time!

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

      Hi Dre,
      Thanks for writing. Medical science loves promoting exciting terminology – such as ‘stem cell production’. Not surprisingly, stem cell injections are now big business, whether in cases like yours or (especially nowadays) in order to heal from Long Covid. I’ve had numerous clients come to me because they’ve really not seen much improvement through expensive injections.

      The fact is that stem cell production is only a minute slice of the entire ‘healing pie’. If you’re trying to avoid surgery on your rotator cuff, then there’s certainly a chance that fasting will help, but a lot is going to depend on the severity of your injury, the length of your fast and the strength of your immune system. Unfortunately, I can guarantee you that – although 92 hours is a good start – it certainly isn’t long enough to allow the depth of healing required to resolve your issue. 10 days is likely to be a bare minimum. Without knowing more of your details, I suspect you’ll need to fast considerably longer than that too.

      Hope this helps,

  4. Michael Massetti Avatar
    Michael Massetti

    Does consumption of coffee or beverages with 0 calories (Stevia) impact the fast at all? Thank you.

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

      Hi Michael,

      Thanks for writing. The short answer is YES!!! Coffee is both acidic and contains caffeine. Over an extended fast, the acids can cause both acid reflux and an intensification of other detox symptoms – given that all products of detox are themselves acidic to begin with. Caffeine accelerates metabolic rate, when instead you should be slowing down in order to maximise healing. Certain well-known MDs do promote the use of coffee for fasting, but unfortunately it seems they don’t understand the difference between short-term and long-term fasts. Don’t get me wrong, I do love a cup of freshly ground coffee in everyday life, but I would NEVER fast with it.

      Stevia doesn’t contain calories, so to that extent it won’t interfere with ketosis, but the sweet taste is going to do nothing to help you overcome your addiction to sweets and sugars!

      Hope this helps,

  5. Hello Sir, I started a fast and wanted to fast for 10 days but I stopped at day 6 because my friends noticed I had jaundice in the eyes. I am wondering why this happened and should it be of concern? Is it OK to continue to fast?

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

      Hi Charles,
      Thanks for writing. When the liver becomes overloaded and is unable to process the blood to the fullest extent, jaundice in the eyes is a common consequence. I’m afraid that without discussing the details of your case in person, I can’t comment on whether it would be safe and suitable to continue. However, I would always urge people to err on the side of caution, especially if they don’t have personalised advice from a fasting expert. In that sense, you did the right thing to stop.
      All the best,

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.