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

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.

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.

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  1. Bradley says

    Hi. I decided to fast a few days back…. I started with a 36-hour fast. It wasn’t strictly water but it was calorie-free. I’m thinking I’ll adjust myself to just water. I definitely felt kind of cleansed like I was removing toxins from my body…. I’m no stranger to ketosis as I’ve done the keto diet in the past. And I put C8-C10 MCT oil in a smoothie every morning (although I didn’t when I was fasting) so my body might be somewhat adjusted at this point to producing ketones.
    I want to work myself into pure water fasts and eventually longer fasts like the 7-10 day fast. I do have a bit of a worry with malnutrition from longer fasts. I know the point is to turn off digestion. Do you think a sublingual geriatric multivitamin would be beneficial when doing an extended fast? There are a few different ones available online. It seems to me like that would be helpful and bypass digestion. Thanks and I’m very grateful to have discovered this website.

    • Tallis Barker, D.Phil. says

      Hi Bradley,
      Apologies for the delay in responding. There’s been a glitch with messaging on the website.
      When water fasting, if you want to maximise cleansing and healing, it’s best to avoid all supplements (assuming you’re not suffering from a chronic nutritional deficiency). The strength of a water fast is in much more than just switching off digestion. It’s a complete transformation from an anabolic everyday state to a catabolic metabolism. Any supplement – calories or no calories – is going to interfere with the degree of catabolism and also therefore with the cleansing and healing promoted by a catabolic metabolism.
      All the best,

      • Valorie says

        What about elimination? On other fast they recommend enemas.

        • Tallis Barker, D.Phil. says

          Hi Valorie,
          There are pros and cons to everything – including enemas. If elimination is taking care of itself during a water fast, there’s no need to think about doing enemas. If possible, it’s always best to let the body get on with things by itself! However, when symptoms suggest that toxins are building up in the colon, then the occasional enema is always a good idea to give support.
          All the best,

  2. Chris Graham says

    Hi Tallis, can water fasting help with nerve damage from surgery? I did a 10-day water fast witch didn’t help. I am wondering if a longer fast like a 21-day water fast will help.

    • Tallis Barker, D.Phil. says

      Hi Chris,
      Thanks for writing. I’m sorry you didn’t experience an improvement to the nerve damage with your 10-day fast, but to be honest, I do think you’d need to fast considerably longer. Exactly how much longer is hard to say, but healing to the nerves can and does take place especially on 21+ day fasts. I’ve sent you an email in response to the contact form you filled out.
      All the best,

    • Aleksandra says

      Hi Chris Graham! Try energy healing or kundalini meditation in combination with the water fast 🙂 Good luck ❤

  3. Linda says

    Hello Tallis and thank you for the blog! I’ve decided to water fast for at least 21 days, my aim is 40 days. I suffer from hearing the Hum for already 10 years after being irradiated by mobile phone masts for 1 year. My life turned to hell with sleep deprivation, loss of functionality, loss of creativity and my libido. I’m just a shadow of my previous self. Since I know the Hum is external (I can’t hear it under water or when I fill in my ear canals with olive oil drops), I would love my brain to switch off back to normal whereas I would not perceive the Hum as in the past! I want my life back! I can’t cope any longer with the Hum, I’d rather die!
    I am on antidepressants and anti anxiety drugs for years now because of the Hum. Is it wise to stop them during the water fast or I’d better don’t do it due to the risk of significant withdrawal effect, I know people have committed suicide?…
    Do you think I would have any success if I still stay on the pills?
    Can I take Senna for bowel movement?
    And last, how I must do the food reintroduction, is there any particular scheme?
    I hope I’ll manage the 40 days, as for me us a matter of life or death (existence with the miserable low frequency Hum).
    I’m on day 3 currently, the only thing that I afforded was a bit of bitter coffee (is this allowed?).
    How about managing your electrolytes imbalance during the fast?…
    Many thanks for your reply!!!

    • Tallis Barker, D.Phil. says

      Hi Linda,
      Thanks for writing. There are a lot of questions here, and I’ll answer the ones which I can give a clear response to, without knowing more context.
      — It’s a good idea to avoid laxatives if possible. Many people with constipation find that an extended fast restores balance, and continuing with laxatives doesn’t allow your body to find its new healthier rhythm.
      — It’s never a good idea to drink coffee while fasting! It’s acidic and often causes problems in the gut, including reflux and even nausea.
      — In order to maximise healing, it’s almost always worth undertaking a fast without electrolytes. In this case you need to manage drinking during the fast and diet beforehand, as well as understand the signs of imbalance – although this is highly unlikely before 40 days.
      — Managing meds is something you should discuss with an expert. It’s usually best to reduce or eliminate them – when this can be done safely!
      Hope this helps,

  4. james swain says

    Hello I love the read. I started fruit shakes 4 days ago omad aswell. I’ve done fasting in the past. I’m on day 2 of a water fast and I feel sick then ok. Sick then ok. When I feel sick that must mean I’m burning garbage toxins. Correct. I’m gonna try for 10 days. WhAt would you recommend would be the best fast for a total cleanse longer maybe. Thanks so much man

    • james swain says

      Oh ya. I would like to add. I am also doing this to quit smoking and to quit drinking beer. I am a weekend alcoholic I do work. Have a full time job. Thanks man

      • Tallis Barker Ph.D. says

        Good for you – then keep it up!
        Your body will thank you for this,

    • Tallis Barker Ph.D. says

      Hi James,

      Thanks for sharing. Well, in terms of the best fast for a total cleanse: the longer the better! There’s nothing more powerful than 40 days!

      But it’s also true that a 10 day fast is ideal for detox. Usually, the first 10 days of a fast are the rockiest in terms of detox symptoms, after which things usually smooth out. This is because the body has already done a lot of the necessary maintenance cleansing by this point. So if you only ever stick to 10-day fasts, this is a great insurance policy against toxins building up over the years and causing a breakdown in health later in life.

      All the best,

  5. Randall says

    Hello sir! I have been doing intermittent fasting for about 10 weeks(18 hr fast). I am 51 and weighed 257. I started a few weeks at 2000 calories and dropped to 1500 calories. The last 2 1/2 weeks I dropped to 950 calories with protein shakes and salmon. I did high protein(125g) and would rotate one day higher good carbs with the protein and other day with higher good fats and protein only. I don’t know a lot just by reading. We ate at my mother in laws house on Friday 1500 calories and I started my water fast after that. I am at 55 hours as of now but I read a article to make sure your gut is ready to do a water fast and food doesn’t get stuck in you after your intestines slow down. They called it food rot in your stomach. Hope that does t happen? I am determined to do a 7-10 day water fast. Before the water fast I had lost 40 pounds from intermittent fasting. Is pedialyte ok? I read another article bout electrolyte imbalance? Is it ok to take cleanse tablets or probiotics during the water fast? Have a lot to learn just want to try to heal my body from all the years of eating bad. Thanks for any help sir!!

    • Tallis Barker Ph.D. says

      Hi Randall,

      Thanks for writing. To answer your question: yes, it’s a good idea to do a dietary transition before a water fast in order to help clear the gut. However, you’ll survive a 7-10 day water fast even if you didn’t. The excess food from not transitioning does produce toxins as it rots. If you feel the effects of this, though, you can always do an enema to help clear things out.

      Re. pedialyte: you should know that it contains sugars (albeit not so much), and this counteracts your water fast – especially if you’re drinking lots. Taking electrolytes of any kind also reduces cleansing. I’ve seen this in countless cases. Yes, electrolytes make you feel better – which is why it’s such a popular sell!!! – but putting anything into your body slows down the process of getting things (ie toxins) out.

      All the best,

      • Randall Dills says

        Thank you so much for the advice and tips!!!

        • Tallis Barker Ph.D. says

          You’re welcome!
          Good luck with your fast,

  6. Ratha Krishnan says

    HI Tallis,

    I just completed my 36 hour water- fasting which is the first time in my life. I am now planning for weekly 48 hour fasting before graduating to 3 days and then 5 and 7 days in that order. I have a chronic increased liver enzymes and am type 2 diabetic. I also have sleep apnea. Will fasting heal these conditions?


    • Tallis Barker Ph.D. says

      Hi Ratha,

      Congratulations on finishing your first ever water fast! May it be the first of many :-). You have a sensible plan to build up to longer fasts. Just make sure you don’t rush things and force yourself into fasts which feel too long. This is the key to building up a good relationship with fasting!

      Once you feel comfortable with 7 days, you’ll probably start to notice that your health issues begin to improve. There are never any guarantees, but the kinds of hormonal issues which relate to liver enzymes and diabetes almost always start to respond to fasts of about a week or longer. In the meantime, your shorter fasts will do some good preparatory detox as well as to help make your body more efficient in healing when it does come time to a 7 day fast.

      Good luck and best of health to you,

  7. Nicolae Dumitrescu says

    Hi Tallis, did you or anyone you know experienced high anxiety after passing approximately 20h without food, what shoul i do?, should i continue or not?, my longest fast was 40h, but i had constant episodes of anxiety on and off, i suffer from hashimoto , with full hypothyroidism, i take synthroid and hormone level is optimal, what are your recommendations?

    • Tallis Shivantar says

      Hi Nicolae,

      People often feel anxious when they first start water fasting. It’s completely natural, because the lack of food awakens the animal instinct to survive – even if, rationally we know we’re not going to starve to death :-). Any addictions to specific foods as well as eating disorders only add to this.

      As someone with Hashimoto’s, fasting definitely has the potential to help you. But unless you have a specific urgent reason to do a long fast now, I’d suggest starting out slow, taking little steps, gradually increasing the length of your fasts so it feels more manageable. In time you’ll be able to build up the length of your fasts WITHOUT ANXIETY so that you’ll reach the point that hopefully you’ll begin to heal the Hashimoto’s through longer fasts.

      All the best,

    • Leney San says

      Just speaking from experience and reading plenty – Fasting has always been a spiritual experience to get closer to God (in
      nearly all cultures) . This same thing happened to me. Prayer and reading scripture should help with this.

      • Tallis Shivantar says

        Hi Leney San,
        Yes, fasting has always potentially been a spiritual experience – so long as you’re open to letting spirit in. Prayer and reading scripture can help if you belong to a specific faith. Alternatively, just trying to Be and centre yourself in your body and in the present moment via mindfulness can also help if you want to go deeper spiritually but don’t subscribe to any particular religion.
        All the best,

  8. Rahul says

    Hey Tallis

    I am embarked on a 14 day fast and at day 5 at present. I am having an acid reflux and heart burns. Can I use some eno fruit salt in the water or is there any natural alternative?

    • Tallis Shivantar says

      Hi Rahul,
      Unless you’re already highly sensitive in everyday life, the most usual cause for acid reflux during a water fast is over-stimulation of the stomach through drinking too much water. My first advice would be to reduce intake and drink only when you’re thirsty. How much are you drinking per day?

      • Rahul says

        I am drinking about 2.5 litres a day and my acid reflux only gets worse.

        • Tallis Shivantar says

          For people with reflux 2.5 litres per day is a lot. Unless you’re severely detoxing, you could easily get away with drinking less than half of that per day – at least until the symptoms improve. Most people see their reflux respond pretty quick to a reduction in water consumed, so I’d recommend giving it a go as soon as possible.

  9. John Catlin says

    Hey Tallis,

    I’m curious – have you ever monitored someone on a water fast that was also dealing with a sinus infection? I’m on day 15 of my water fast, and I’ve been fighting sinus congestion throughout these 15 days. Today is the day where I’m finally getting to the tail end of the coughing and wheezing. (Originally, I was going to do a 14 day fast, but now I’m extending it to 21.)

    I’ve thought about taking bromelain which is said to help fight sinus issues, but at the same time I still wanted to strictly keep to water. I know you can’t give specific advice, but what are your general thoughts on a situation like this?

    Best regards,

    • Tallis Shivantar says

      Hi John,

      Yes, sinus infections can take a while to clear up while fasting. Sinus inflammation is also a classic detox symptom during a water fast – something which can last through days if not a week or more. So perhaps you’re experiencing a combination of both of these factors.

      I personally prefer to keep my water fasts pure whenever possible, but you also need to be practical. If your sinuses are ruining your life at the moment while fasting, a little bromelain isn’t going to kill you – especially since it’s a natural enzyme and not a synthetic drug. Do be aware, though, that bromelain is only going to treat symptoms and not the root cause of your issue. Only fasting will do that!

      All the best,

  10. Vic says

    Your website has been the right inspiration for me which I needed. Today I’m in my 7th day of my 21 days water fasting. I’m doing fine and I feel great! Thank you Tallis.

    • Tallis Shivantar says

      Hi Vic,
      Thanks for sharing :-).
      That’s great you’re doing so well – and especially for someone undertaking their very first water fast. Without a lot of prior experience, most people would be frightened by 21 days! I know I would be :-). Your positive mental attitude is a huge asset!
      Congratulations on finishing your first week,
      Keep it up,

  11. Polly says

    Thank you so much! I plan to water fast at least twice a year! I am using it to cleanse my body from animal product and start my vegan diet! So no I plan to make it enjoyable and a lifestyle change! Your website and videos are inspirational and I will keep you abreast of my journey! Blessings

    • Tallis Shivantar says

      Then bon voyage, and do let us know how you get on 🙂

  12. Polly williams says

    I am starting my water fasting for the first time in my life. It is a physical and spiritual cleansing for me. Wish me success as I know this is what my body needs.

    • Tallis Shivantar says

      Hi Polly,

      I do wish you success 😊, especially now as you begin your journey. If I can give a word of advice: let this truly be a journey and not something you simply try out now this once. To maximise long-term success and health, don’t push yourself too hard this time, so that it feels like ‘too much’ by the end. Fast with love for yourself and for your body, so that you want to return again to water fasting in the future. Long-term health is never achieved through just one fast, but rather by gradually building water fasting into your life, little bit by little bit, so that it becomes easier and easier, and more and more enjoyable.

      Wishing you all the best and a Happy New Year,


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