Warning: Creating default object from empty value in /home/customer/www/chewsomegood.com/public_html/wp-content/themes/salient/nectar/redux-framework/ReduxCore/inc/class.redux_filesystem.php on line 29

Warning: Use of undefined constant PWP_NAME - assumed 'PWP_NAME' (this will throw an Error in a future version of PHP) in /home/customer/www/chewsomegood.com/public_html/wp-content/mu-plugins/wpengine-common/wpe-sec.php on line 63

Warning: Parameter 2 to WPE\Site_Preview::the_posts() expected to be a reference, value given in /home/customer/www/chewsomegood.com/public_html/wp-includes/class-wp-hook.php on line 308
How To Heal Your Gut With Fasting

How To Heal Your Gut With Fasting

Fasting for IBS

The idea of skipping a meal or two may not sound too appealing to most of you. It might seem counterintuitive in fact, especially since we are used to eating on average ~ 3 meals a day.

Days are stressful and food is rewarding. I get it. Sometimes we need that crutch just to get us through the day. Not just that, but without food you feel moody, drained and just generally depleted.  Thats why the very idea of going without seems crazy.

But, if you have IBS or a leaky gut, then chances are that food, even ‘safe’ foods sometimes make you feel like that anyway. So you’ve got nothing to lose, right?

Im going to throw in a quote which I think applies to fasting pretty nicely:

“I’m convinced that the best solutions are often the ones that are counterintuitive – that challenge conventional thinking – and end in breakthroughs” – Nathaniel J. Wyeth

As much as I like quotes, I like science more. Lets take a look at some of it, and see why fasting might be a legitimate approach to dealing with an irritable bowel.

Digestion requires effort

When you eat, your body goes to work breaking down, assimilating and absorbing those nutrients. This requires a degree of labour for your digestive system – about 25% of the calories from each meal.

When you digest food, your body shifts its focus and resources away from other physiological processes, like growing and repairing. Your immune system also has to be on alert, screening what passes through the gastrointestinal tract.

If you eat 3 meals a day, and have a few snacks in between, then chances are that your digestive system hasn’t had much time off.

Overloading the digestive system isn’t ideal, even for the most robust of guts, let alone an irritable one.

When you eat, you instruct your body to digest what goes in it. This alters the way your genes are expressed – how they behave. So why is that a big deal?

So, the heavy digestive work takes around 7 hours give or take, until you start heading towards a fasted state. Its only after that 7 hours that the digestive process cools off. As you may be thinking right now, its not often that 7 hours goes by without at least a coffee, snack or meal, in daylight hours at least. Anything that has to be metabolised will change your gene expression away from a fasted state.

Fasting alters your physiology

It turns out that when you aren’t processing food, your genes actually begin to express themselves in a very restorative manner. You could call it healing mode.

This is the counterintuitive part. Fasting is distinct from starvation. Skipping a few meals, a day or even a few days as part of a water fast isn’t going to kill you. Whereas starvation eventually will. 

When you fast, you actually shift your energy pathways away from using glucose (sugar) and start to burn fat. Your body only has ~ 2,500 Kcal of stored glycogen to use as glucose. But, it has > 100,000 Kcal of stored fat to burn as fuel.

It takes time to shift towards fat burning pathways, which is why you may feel crappy until day 2/3 of a prolonged fast. A study that fed mice within an 8 hour window (16 hours fasted) found fat oxidation to be significantly increased. This suggests that fasting could promote better use of fat as fuel in humans, so you wont starve.

Besides just surviving on fat, your body also shifts towards some other beneficial adaptations.

Inflammation is at the root of many, many chronic diseases. It is something that our modern diet and environment does quite well at inducing. IBS, and leaky gut are not so different to inflammatory bowel disease in one respect – there is a degree of chronic inflammation at work. In fact, this inflammation is what causes damage to the gut wall allowing it to ‘leak’. You’ve even got these leaks to thank for some of your symptoms.

Bottom line is that Inflammation sets the bowel up for irritation.

Regular exposure to environmental toxicity (which exist on foods), allergenic foods, processed food, drugs, alcohol, even some medications – they all cause inflammation. These are the things that pass through our GI tracts all day everyday!

Its no mystery that a bowel can become irritable when overloaded with toxicity. This is compounded by the fact that stress is inflammatory. I don’t have to tell you how much your bowels are affected by stress.

Back to genes.

When you fast, nothing passes through your GI tract except water. Not only does this stop the flow of potentially inflammatory compounds, it reduces inflammation even further. When in a fasted state, there is greater activity of anti-inflammatory cytokines, and less activity of pro-inflammatory cytokines – this puts the body into an anti-inflammatory, disease mitigating state. Your genes know when you are fed or not, and they instruct these changes.

Inflammation & Oxidative Stress

Fasting reduces oxidative stress via your genes. This is the damage that occurs to cells from exposure to toxicity. The proteins, lipids and DNA of cells are actually affected, and ultimately change the function of those cells. This process is exactly what anti-oxidants prevent, so its important to activate them within you, and eat them when not fasting. 

Interestingly, the development of IBS is linked to increased levels of oxidative enzymes, and reduced activity of antioxidant enzymes. This is what causes progressive damage to your cells, retarding their function.

Cells matter, after all they make up the organs which handle digestion. Progressive damage to even one organ in the digestive system can throw the whole process out of line, producing symptoms of IBS.

Fasting may be a powerful intervention for IBS and a leaky gut due to the reduction in oxidative stress. Whilst exposure to toxicity is minimised and inflammation subdued, the cells of the body may have room to regenerate.

Fasting & The Migrating Motor Complex (MMC)

At the root of many IBS symptoms are the bacteria in your gut. You’ve probably heard of SIBO (small Intestinal Bacterial Overgrowth) and dysbiosis (microbial imbalance). This basically means the microbial community is out of whack, which often causes the gut to become leaky.

Interestingly, fasting might actually help reshape the composition of the gut microbiome. This is under control of the MMC.

The MMC is a mechanism which controls stomach and small intestinal contractions in a cyclical pattern over a period of ~ 2 hours. Its function is to essentially perform housecleaning throughout the GI tract, sweeping bacteria and undigested food particles out for elimination. 

The MMC is instructed by a complex orchestra of Neurohormonal signals in response to feeding/fasting, including but not limited to Ghrelin, Motilin, Serotonin and Somatostatin.

MMC activity peaks in between meals, in the absence of food. The presence of food and nutrients interrupts and decreases MMC activity, and essentially steers hormonal control back towards digestion and assimilation. 

When the MMC is given the time and space to do its thing, it becomes more difficult for food and bacteria to hang around. This is why fasting could be a viable anti-SIBO measure.

Patients who had SIBO also had an absent or disrupted MMC pattern. IBS patients had a shorter duration of motor activity when compared to healthy counterparts.

In time restricted feeding studies (type of fasting), TRF restored a variety of beneficial strains of bacteria in mice.

When and how you decide to eat can induce changes in the gut microbiome that contribute to the diversity of gut microbes. This presents a mechanism by which those bacteria affect us, our metabolism, immunity and digestion!

There is only one study (that I know of) that has investigated the effects of fasting on IBS specifically. The results were quite promising.

36 subjects underwent fasting therapy for a period of 10 days and were progressively re-fed for 5 days after. Compared to the 22 subjects in the control group (conventional pharmacotherapy), the fasted group reported a significant improvement in symptoms. Those symptoms were abdominal pain-discomfort, bloating, diarrhea, anorexia, nausea, anxiety, and interference with life in general. The control group only reported improvements in 3 symptoms – pain, bloating and life in general.

Although the 10 day controlled protocol is hard for me or you to replicate, it is worth seeing what a less severe protocol could do.


You don’t have to starve yourself to fast. Starvation is different from fasting. Think of fasting as a kind of strategic way of eating. Whereas starvation is just not eating at all, until its time to check out – not ideal. 

There are in fact many ways which you can choose to fast. The most common fasts include water only. Longer water fasts > 48 hrs may require micronutrient and electrolyte support, in addition to supervision under a professional. 

If you choose to do it intermittently, the idea is to limit the window which you consume food in, and fast for the remaining 24 hours. 

You can start with:

  • 12 hours fasted // 12 hours fed
  • 14 hours fasted // 10 hours fed

Then progress onto:

  • 16 hours fasted // 8 hours fed (repeat every other day)
  • 16 hours fasted // 8 hours fed
  • 19 hours fasted // 5 hours fed
  • 20 hours fasted // 4 hours fed 
  • 1 day fasted // 6 days fed

You might choose any of these and do them intermittently, mixing up the windows which you eat in. Have a play around and see what works for you.

Prolonged Fasting

  • 24 Hours – from dinner to dinner / lunch to lunch. You effectively eat once/ day which you can do a few days/week.
  • 36 Hours – eat breakfast on day 1, then fast for all of day 2 to eat breakfast again on day 3. You may choose to do this 1 maybe 2 times a week initially for a big gut healing push. Then continue with shorter fasts.
  • Fasts beyond 48 hours can be done but require support with micronutrients and supplements. Make sure you know what you are doing with these.

Join the discussion 29 Comments

  • Priya says:

    I saw an article on how to do elimination diet 2 days back on your website. Today I can’t find it. Please post the link. I have AI disease – AI thyroiditis. Thanks

  • Em says:

    Hi I am first trimester pregnant, with an under active thyroid, lots of gut issues but unsure what I can and can’t do during pregnancy, any advice?

    • Rory says:

      Hi Em. Congratulations on your pregnancy!

      Any drastic dietary changes during pregnancy wouldnt be advisable (like elimination diets, mid to long fasting, wide restriction of certain foods / food groups) as your baby and you will require a great deal of varied and quality nutrition. However, if you have any known food allergies, sensitivities and intolerances, it might be worth removing those foods (please run this by your doctor and consult a nutritionist/dietician as well). A functional medicine practitioner is also worth consulting.

      Removing poorly tolerated foods will promote better absorption of other nutrients, helping you and your baby extract more nutrition from well tolerated foods. Bear in mind that removing common problem foods like gluten/dairy will mean you miss out on the nutrients that also are contained in those foods (Zinc, B vitamins, fatty acids), so its worth making sure that you are eating other foods which compensate for this. In many cases, poorly tolerated foods can drive thyroid issues, so by working on them it might help your thyroid.

      Its worth going to see a specialist dietician, nutritionist or functional medicine doctor who focuses on pregnancy, and may be able to help guide and implement your decisions throughout your pregnancy.

  • AndyJ says:

    Poor article to describe fasting. Starvation happens after all your fat and mineral reserves have been used up, that can take 20-50 days depending on fat stores.

    • Rory says:

      Hi Andy. Thanks for outlining the difference between starving and fasting. “Just because you can starve if you don’t eat, it doesn’t mean that skipping a few meals, a day or even a few days is going to kill you” – is making the differentiation between straight starvation and fasting (skipping a few meals/days as opposed to not eating at all).

  • Lawrence says:

    What micronutrients and supplements would be needed in conjunction 48+ hour fasts?

  • Lawrence says:

    I ask because I use bone broths, “super greens” powders, natural B vitamins (beef liver pills, rice bran and bee pollen), Vit A and D from Cod liver oil, magnesium, L-glutamine, glycine and other amino acids currently and would basically continue them through fasts I do. Would these be enough to cover 48+ fasts?

    • Rory says:

      Hi Lawrence – great question. It really depends on what your end goal is with fasting. It sounds like you’ve got many of the essentials covered to upregulate phase I and II detoxification pathways, and by supplementing glutamine, glycine and cysteine you’ll be getting some good glutathione support. You could also use betaine from beets, and sulfur from cruciferous veg to support sulfation and methylation. If you wanted to try to optimise fat oxidation, you could play around with vitamin C and Carnitine. I use BCAA’s to offset any muscle catabolism I can.

  • Lynn says:

    Great post! I’m trying to solve a histamine intolerance, which is no doubt caused by leaky gut. For the past 5 weeks I’ve eaten nothing but sweet potatoes (in one large meal at 7 a.m.) in an effort to give my gut time to heal. I’m planning to continue until the end of February at least. What’s the typical healing time for leaky gut? Should I do some 2-3 day water-only fasts to speed it up?

    • Rory says:

      Hi Lynn, thanks for the feedback. Its hard to say exactly how long it will take for you specifically, but there are certainly ways to expedite the process. Whilst some time off for the gut is beneficial, giving it a little love with specific nutrients wont hurt either. So a good strategy may involve a good balance between fasting and feeding cycles. You could do 2-3 day water fasts periodically depending on your preference (could be 1x a week/month), and support with strategic nutrition, especially collagen, vitamin C, A, D , Zinc, turmeric, and high quality proteins (like fish and chicken) and amino acids like glutamine (in addition to your sweet potatoes!). In this way, the gut has time away from inflammation, and is supported with the resources it needs to rejuvenate, so long as you continue to avoid histamine containing and producing foods, and any other intolerances that you may be aware of.

  • Denise says:

    I just got the results of a microbiome study back and they are not good. The results show that the positive bacteria in my stomach are nearly completely depleted. I have tried different things and while I know I have intolerances and have developed a few (possibly false positive) allergies, I seemed to do best during intermittent fasting (my regime was to eat until I was no longer hungry but never full and fast one day a week) but kept getting pains in my stomach when I would try to exercise–just walking. Any advice for what I should take supplement-wise (my stomach has never tolerated supplements very well), exercise habits to begin, or possibly just not do on fasting days, or anything else I could use? I had been trying a modified elimination diet this week with some good results but thought maybe a boost could be needed to speed up healing. I am on my feet all day, so I’m not sure if multiple fast days would work, although I was thinking of every other day.

    • Rory says:

      Hi Denise, thanks for your comment. Its hard to suggest supplements without knowing what you need them to do. If you are having problems with your stomach, you might consider consulting a functional Medicine Practitioner who can assess your gastric function (like stomach acid strength and secretion) and whether H.Pylori infection might be at play (which could account for down stream food intolerances) with Labs.

      Qi Gong and Yoga are excellent, gentle ways of massaging digestive organs, restoring nervous system tone (which regulates bile secretion, stomach acid secretion and digestive enzyme secretion) and ultimately helping you to extract your nutrients from your food, and balancing HPA (hormonal activity) such as lowering cortisol, and increasing serotonin (which helps regulate gut motility, and will help prevent GI disturbances like SIBO and dysbiosis).

      As fasting goes, do what you can reasonably sustain without risking not getting sufficient nourishment to support GI restoration. If you are already doing an elimination diet, that limits what you can consume, so be wary of going overboard with fasts.

  • Alyson Guin says:

    Your site is so fantastic. I’m going to come back here again.

    • Rory says:

      Thank you Alyson! Much appreciated. If you would like to suggest any other topics you would like to know about, please leave them in the comments!

  • Yvette says:

    How can I go from time restricted eating to prolonged fasting? Would I suddenly go from time restricted eating to full days eating, except from the one full fasting day in the week? And what do you think is more beneficial for healing the guts: to do a 20-4 fast for some months (maybe with three whole fasting days per month) or a weekly two-days-fast for the same period of time (with or without IF on top of that)?

    Thank you very much!

    • Rory says:

      All great questions, and I understand that it can be confusing to weigh up the many different options at your disposal.

      Whilst we all like to seek out that one gold standard protocol (whether it be fasting, detoxification or other….), it remains elusive because of the fact that theres no one size fits all when it comes to our unique genetic, biochemical etc makeup.

      A good way to orient your protocol will be to use your symptom reduction as a qualitative means of telling whether what you are doing is working for you or not. If you want to get quantifiable data as well as qualitative, you could look into some functional tests to pinpoint various aspects of gut function when you want to see your progress reflected by data.

      The tests you select depend upon what you think may be going on in the gut:

      1) SIBO
      2) Dysbiosis
      3) Candida
      4) Parasite
      5) H.Pylori
      6) Complete blood count and metabolic panel (assesses yeast or parasite infection)
      7) Organic acids microbial markers, IgG food sensitivities, celiac panel
      8) SIgA and leaky gut test
      9) Short Chain Fatty Acids
      10) GI Inflammation

      All of these tests can be found at http://www.biolab.co.uk/, https://www.gdx.net/uk/ (GDX also has US brach), and https://www.greatplainslaboratory.com/

      Trial and error is the very means by which you are able to pinpoint what works and what doesn’t. So, you could systematically test out each of your suggestions making sure to track what you are doing.

      If you are able to sufficiently nourish yourself within a time restricted feeding protocol (calories and nutrients), then adding in a day or two of straight fasting / week on top of that might be doable.

      If you find that you are unable to consume the necessary food intake with TRF everyday in a sustainable way, then you may opt to do TRF for say 3 days a week, 3 days of full eating and 1 day of full fasting.

      You might also retain your TRF schedule, but expand the feeding windows to accommodate enough nourishment so that you can throw in 1-2 days of straight fasting as well.

      Select what you feel is sustainable for you to keep up for however long you choose (1-2 months EG), and make sure not to overdo it as to ensure you take on the supportive nutrition which also helps settle the gut. Do what you feel works for you, whether that be 20-4 or 2 days a week full fast. Find out by testing each for a given time period.

      Also, you might decide to do a 3 day prolonged fast 1 x month with TRF the rest of the time for a while. You can explore your options by incrementally pushing your extended fasts (> 3 days you’ll need to provide nutritional support with broths, protein supplements and veg juices etc).

      Hope this helps

  • Eric says:

    I love your site. Just to explain my situation….. i did colonics for a while in 2012 and since then my stools were soft to runny for 5 years. I became vegetarian to see if that would help, it did a little bit then went back to being plop dropping when going to the bathroom. I could see oils floating in the toilet and obviously the water was not wicked. I had digestive problems for past 5 years prior or more. I went fully raw vegan Two 1/2 years, kimchi, sauerkraut fermented foods, salads daily and saw huge improvement but still bowel movements still too soft and wipe after wipe to get clean. My girlfriend suggested we begin streaming foods like potatoes and mixing with our salads, major progress for over a month but then again not fixed, now I eat steamed veggies because it’s what gives me the best results, but I am on borrowed time, always tired, Feel weak, do light exercise and I look fit, but don’t feel it. supplement to get b12 and anything I might be missing. As I write this in my 3rd day Of an intestinal infection because I have almost no stomach acid. I was planning on fasting 24hrs 2x a week, begin taking collagen, juicing red garbage juice w/pulp every other day as first meal before solid foods to help recolonize gut along with other prebiotics and whatever micronutrients would feed them and begin taking bitters regularly to get bile production underway, was going to take raw apple cider vinegar before meals to increase acidity in my stomach. I was doing Gul stone protocol colonic when this happened and I did not get stones. I though maybe I had blocked bile ducts which would explain not digesting the fats anda seeing them in my stools. I put oil on my salads and foods and have no pain or problems digesting. I am just looking to recolonize gut and appreciate any suggestions maybe how to get stomach acid levels back up, I am Concidering different methods and would appreciate any suggestions you may have.

    • Rory says:

      Thanks Eric. The stomach acid issue is key here as you suggest, and there are a lot of things which could be inhibiting its production. Have you ever heard of/considered an elimination diet? This helps systematically test foods. Subtle food intolerances could be interfering with stomach acid production, and causing the downstream effects in the intestines. You could also pair this with a gut microbiota panel, and assess which species are present/vacant. This might provide an indication as to bacteria that may be disrupting bile acid conjugation and fat absorption. In addition, B-glucoronidase producing bacteria could be overgrown and be causing you to reabsorb toxicity which is meant to be eliminated – perpetuating your fatigue etc.

      Deep, diaphragmatic breathing is also key for full innervation of gastric acid production, so a daily breathing/relaxation practice can help bring the nervous systems tone to a state more conducive to good digestion. You can get tests done for H.pylori and dysbiosis from a naturopathic/functional medicine practitioner as well. Once you have a look at these, they might provide you with antimicrobial herbs, probiotics and prebiotics to balance things out.

    • Sean Johnson says:

      You might consider having your gallbladder tested. Ultrasound + HIDA Scan. I have Biliary Dykinesia, and have had problems for about 3 years. Due to the multiple responsibilities of bile in the body, problems with it can lead to all sorts of issues, including issues with the small intestine. It’s not just for emulsifying fats! I’m still on a journey to fix this issue without removal, but haven’t completely solved my problem. At least with having it tested, you’ll know of any abnormalities.

  • The questioner says:

    Water only or dry fasting are completely different to starving. The term starvation is when the body has used up it’s adipose tissue or fat stores and the body starts using vital tissues in order of value. That’s starvation. Fasting is when you refrain from eating and your body burns up glycogen stores – usually 2-3 days worth and then switch into burning stored fat or adipose tissue. The correct term for that is water only fasting. A person can fast – depending on their individual circumstance – for upwards of 60 days. A water only fast over 3-5 days should be done with medical supervision, meaning someone who has conducted thousands of long fasts especially for the re-feeding which needs to be done with great care so as not to harm the body.

  • ami says:

    Hi, If I weigh 53kg (20 years same weight approx) 42 years old male 5.7 inches tall but no disease and low appetite. If I water fast 3 days will I be able to fix digestion & gain weight after the fast? (recovery). FastingByEmaciated by shelton says its true

  • Stephen says:

    Thanks for this very helpful article. I’ve fasted many times since becoming a Bible-believing Christian 20 years ago and have seen amazing results in mind, body, emotions and spirit. It’s good to know the specific biology behind it all.

  • Abdul says:

    Rory, I ended up here because I am currently on day 7 of what was diagnosed by my Doctor (Senile old man who is on the brink of retiring and seems only to be concerned with seeing as many patients as possible as quickly as possible) with IBS. The pain I went through was extremely difficult to manage, and I have a pretty decent pain tolerance compared to most (I was in tears from frustration, thought I was passing a Kidney Stone). I was literally unable to move for at least 48 hours, and the other 5 days the pain was on and off. I am on month 5 of a ketogenic diet, I typically do Intermittent Fasting – anywhere between 21/3 and 14/8 depending how my day is going.

    Prior to Keto, the smallest bite of any food was almost guaranteed to give me heartburn, bloating, and my #2 hasn’t looked like your typical healthy poo since I was 10yrs old. I’m assuming I have/had a leaky gut. Ketogenic diet really made eating enjoyable again, and helped me reconnect with food as a source of energy and not as a source of mood/emotional balance. I’ve had 2 ‘attacks’ like this prior to being on Keto, but this one is by far the most intense and longest lasting I’ve ever experienced.

    At this point, I’m looking for different ways to do a “reset” of sorts to my entire digestive system since I’m convinced it needs some help, and I was about to go off solid foods for 2-3 days and then reintroduce food slowly and increase fiber slowly + supplement with Bio-K for prebiotics. Someone recommended to look into getting a Colonic, but I feel like that would only be effective if you have a solid plan to rebuild healthy bacteria after that (which I don’t). Do you think I’m on the right path? I’d appreciate any insight you have. Thank you in advance for your reply and also for this great post. Really enjoyed it.

    • Rory says:

      Hi Abdul, thanks for your message. Im glad that the ketogenic diet has provided you with some respite, but if you are still experiencing the attacks then that must indicate a pervasive imbalance in the gut that ketosis hasn’t been able to deal with. Some diet can provide symptomatic relief for a while but may not be geared towards the restoration needed for the gut. In other words, a lot of people end up sticking with a diet that caters to/offsets an underlying imbalance without correcting it, which could be the case here. A 36-72 fast (with water) could help reset any old and confused immune cells, but would need to be followed up with a few months of strategic nutrition for the gut. Do you know if you have any food intolerances/any foods that set you off? If not you can systematically test foods before you put together a regenerative plan, as it would involve avoiding problem foods for a while.

  • Mike says:

    Am I missing something? Eating breakfast day 1, then not eating day 2, then eating breakfast day 3 is a 48 hour fast. You are going without food for 48 hours. Eating Dinner, then fasting all day, then eating breakfast would be 36 hours. Right?

Warning: Use of undefined constant PWP_NAME - assumed 'PWP_NAME' (this will throw an Error in a future version of PHP) in /home/customer/www/chewsomegood.com/public_html/wp-content/mu-plugins/mu-plugin.php on line 114

Leave a Reply