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2020 Extended Fast Experience and Results: GKI, SIBO and a Herx Reaction

by Maggie Jones

It’s been almost a year since my last extended fast and my body has been begging for one. After reading the incredible case study of the woman who completely resolved her stage 4 cancer through fasting and keto alone, I was more eager than ever.

My current fasting routine includes a 44-80 hour water fast each week (Sunday night to Tuesday or Wednesday dinner, sometimes until Thursday morning.) This pattern is important for me to keep my glucose-ketone index in therapeutic range and enjoy the benefits of autophagy — among countless other benefits.

While my last 7-day fast was incredibly uneventful, this one was a bit more exciting because I’ve been grappling with a little something called SIBO.

Read about how to fast and why here.

Fasting and SIBO

SIBO, or small intestine bacterial overgrowth, is when the wonderful bacteria that cultivates your large intestine moves into your small intestine and causes all kinds of trouble. I won’t spend a lot of time talking about it here but suffice to say it can be pretty awful and extremely hard to get rid of. In my case I’d been experiencing terrible constipation and bloating for months. In Hong Kong I’d been able to manage it with regular colonics but, in lockdown London, all my home constipation remedy attempts had failed. After a couple of weeks, the swelling in my gut was painful and made it difficult to breathe at times.

On the left, my tummy while trying on a dress in the weeks before lockdown. On the right, my tummy while distended from SIBO, struggling to breathe, a few days before beginning fast.
Improvements in distention over the course of my fast. Relaxed posture in all pictures.

There are two aspects to treating SIBO:

  • Treat the symptom: Beat back the bacterial overgrowth for as long as possible. Success is called remission but, like cancer, SIBO will always come back unless the root cause has been addressed.
  • Treat the root cause: In my case, the root cause of my SIBO is severely reduced gut motility either because of brain damage or, my hope, a carnitine deficiency.

In addition to my usual fasting goals, I hoped that an extended fast would allow me to starve the bacteria back and buy a period of SIBO remission. Many practitioners believe that a 14 day “elemental diet” or water fast is enough to kill a SIBO infection.

I knew from the beginning that this added twist would make things extra challenging as I’d be facing die-off symptoms.

SIBO Die-Off: The Herx Reaction

Die-off, known more medically as a Jarisch-Herxheimer reaction, or Herx reaction, refers to the body’s adverse inflammatory response to the toxins released by bacteria and fungus as they die. It can range from mild flu-like symptoms to, as I learned, something much more severe.

I warned Brad before beginning my fast that I might be bedridden for a couple of days. I also knew that, during this period of inflammation, my immune system would be depressed and so we made arrangements for me to avoid shops when that time came.

I also ordered a SIBO breath test which I expected to arrive on Day 2 of my fast to confirm my suspicions.

Fast Day 1: An Unusually High GKI

SIBO has made it harder to keep my GKI in the therapeutic zone on days when I eat and I rely on my weekly 48-hour fast to bring it back down.

My GKI was especially high at the beginning of this fast. I peaked at over 25 (!!!) at noon — my dawn phenomenon comes quite a bit after dawn — to just under 3.0 around 8pm.

Overall, since I fast at least one day a week already, there was nothing new about this day.

Inputs: Lots of water, physician-prescribed meds and supplements (lorlatinib, metformin, atorvastatin, doxycycline, mebendazole, beta glucans, melatonin, magnesium glycinate, CBD oil, Vitamin D3, carnitine), green tea.

Outputs: Nada. No bowel movement in over a week.

Fast Day 2: Business as Usual

Except during my dawn phenomenon, my GKI was in the therapeutic range (<3.0) throughout the day and finally dropped to the optimal range (<1.0) after 8pm.

It was a pretty easy day. I love not having to shop, cook, or do dishes!

Inputs: Lots of water, physician-prescribed meds and supplements, green tea, coffee.

Outputs: Still nothing. I have to wait until after the SIBO test to do a flush.

Fast Day 3: Back in Optimal GKI Range

Usually days 2 and 3 are the most difficult. Difficult for me means that my body likes to remind me that there’s food everywhere. Every time I open the cupboard or walk past a restaurant my body says, “Hey, we could eat that.”

This time it was easier -in large part because Brad was fasting with me for the first three days. Days two and three can be a lot less fun when you’re watching someone else eat. Huge thanks to Brad for seeing me through the tough part!

GKI-wise, I was happy to be under 1.0 almost all day.

Inputs: Lots of water, physician-prescribed meds and supplements, green tea.

Outputs: Nada. No bowel movement in almost two weeks. I started taking an herbal supplement called MotilPro to try to restore some motility. I email the SIBO test clinic and they say the test won’t arrive until Day 6 of my fast.

Fast Day 4: Holding Steady

My GKI was steady under 1.0 all day.

To keep my energy high I started supplementing electrolytes – for me that’s:

  • 3 grams sodium (7 grams Himalayan pink salt)
  • 800mg magnesium citrate (in addition to the magnesium glycinate I take each night)

Most people will also need to supplement potassium which can be found in salt substitutes like Morton’s Lite Salt but it’s best to consult your doctor first. I just happen to have naturally too-high blood potassium levels and am under strict medical instructions to avoid extra potassium.

Many people will need to start supplementing electrolytes earlier in their fast. Generally, if you feel weak, shaky, fatigued or headachy after starting a fast, you need more electrolytes. If electrolytes don’t help, it’s wise to break the fast and consult your doctor.

Brad returned to normal eating today but I was past the point of hunger and no longer had any problem sitting with him while he ate. Once I hit day 4, I always feel like I could go forever.

Inputs: Lots of water, physician-prescribed meds and supplements, electrolytes, green tea, black coffee.

Outputs: One tiny rabbit pellet. I’m hoping the magnesium citrate will help as it has known laxative properties.

Fast Day 5: Herx Reaction Begins

GKI remains slow and steady the rest of the fast just wobbling between 0.6 and 0.8 based mostly on exercise and my mood – that little spike in the afternoon was immediately following a small conflict with Brad.

Today is most notable because its the day Die Off Symptoms Begin!

It began with me starting my period. I almost never get my period – this was the third time in a year. Normally I’d think, “oh yay, thanks to fasting my body is healing and my hormones are finding balance.” I knew that wasn’t the case this time, though, because I’d just finished my second period of the year a week ago. I was about 8 months early by realistic accounting, two week early by best case accounting.

I realize now that the bacteria in my gut were dying and creating/ becoming toxins that my body was desperate to eliminate through any means available.

In the evening I started experiencing excruciating pain in my hips. While I normally sleep very well while fasting, I spent the night writhing.

Inputs: Lots of water, physician-prescribed meds and supplements, electrolytes, green tea, bone broth.

Outputs: Nothing.

Fast Day 6: Powerful Herx Reaction

My GKI remained stable and less than 1.0.

Today, my whole focus was on my Herx reaction. The pain in my hips, buttocks, thighs and back was almost unbearable and I spent much of the day in a hot bath, which helped, or pacing the hall since movement also seemed to help. I wasn’t able to complete my daily yoga practice.

I had a sudden, crazy breakout across my back and chest with a couple pustules on my face.

Herx reaction break-out.

It’s like all the poison in my gut was being squeezed out my muscles, joints and skin. I needed to help my body detox and my bowels weren’t helping in the effort. I focused on drinking lots of water, deep breathing exercises, and took some activated charcoal.

The SIBO breath test finally arrived but I wouldn’t be able to take it until morning.

I drank some bone broth in the evening in the hopes of feeling a little better. I spent a restless night writhing on the sofa and pacing the hall in pain.

Inputs: Lots of water, physician-prescribed meds and supplements, electrolytes, activated charcoal, green tea, bone broth.

Outputs: No movement. I plan to flush tomorrow immediately after the SIBO test.

Fast Day 7: SIBO Test and Flush

The SIBO breath test takes 3 hours. I started a Vitamin C flush immediately after.

The SIBO test results confirmed my suspicion that I have a terrible infection of methane-producing bacteria in my small intestine.

Under normal circumstances I reach for the salt water when I need to flush but I was concerned about my electrolyte balance while fasting.

It was my first time using Vitamin C and it will be my go-to from now on. I ended up needing over 80 grams dissolved in water over several hours to achieve the flush. I’m surprised my body was able to absorb that much – a clear indication that my immune system didn’t have all that it needed. While the flush didn’t help with the pain as much as I’d hoped, the bowel and bloating relief was substantial.

Inputs: Lots of water, physician-prescribed meds and supplements, electrolytes, activated charcoal, green tea, bone broth.

Outputs: A satisfying clear-out riding the flush.

Fast Day 8: Refeed

Despite yesterday’s flush, my pain continues and is excruciating.

I start having serious concerns that my immune and detox systems are overwhelmed and the implications for my cancer. Are my immune cells too focused on dealing with the toxins in my gut and leaving my cancer to grow?

If I break fast now, the bacterial that is still alive will repopulate my small intestine within a week. Worse, it will repopulate my small intestine with strains of bacteria that can survive 8 days without food.

If I continue fasting my overwhelmed immune system could fail. My cancer could grow. Also, until I fix the root cause, my gut motility, the SIBO will come back anyway.

And the pain. I’m really good with pain but this is on a whole other level.

I ended up breaking fast that evening. Because my body was in such a precarious place, I was extra cautious about my refeed and took a multivitamin with calcium, phosphorus and B vitamins before eating a simple bowl of leafy greens in broth.

Day 9 & Beyond: Herx Recovery

I resumed normal eating on Day 9. I shouldn’t have been surprised that my symptoms didn’t magically disappear after eating the soup.

  • My false period did stop almost right after refeeding on Day 8
  • The pain reduced over the course of Days 9-10
  • The breakout across my back and chest resolved a week or two after refeeding.

I’ve continued my regular weekly fasts without any problem or hints of die-off.

The constipation and bloating continue after 2 weeks although I’ve made progress against them. The abdominal distention returned within a few days, disappointingly.

Within days of the Vitamin C flush, my SIBO distention returned. When people ask I tell them 6 months and invite them to feel. If I’ve eaten anything fermentable, that bacteria baby is kicking.

A New Strategy for SIBO

I’m now focused on treating the SIBO more slowly with herbal antibiotics and biofilm disruptors that have been shown to be effective against methane-dominant SIBO like mine:

So far I haven’t experienced any die-off symptoms or, if I have, they’ve been too subtle to notice.

At the same time, I’m working to fix the root cause, my lack of gut motility, with the following:

  • Observing discrete mealtimes and not snacking in between. For me this means only eating from 1-2pm and 6-7pm. I’m an inveterate snacker so this has been challenging.
  • Supplemental digestive enzymes and Betaine Hydrochloride with Pepsin at mealtimes to help with digestion.
  • Chewing my food thoroughly and not drinking much water at meals to avoid diluting my stomach acid. I have no idea what that means for soup.
  • Digestive bitters after eating.
  • MotilPro (13mg Vitamin B6, 2g ginger, 1g Acetyl-L-carnitine, 100mg 5-HTP)
  • Acetyl-L-carnitine supplementation (an additional 2-3g daily as I have a documented carnitine deficiency that could be causing a weakening of smooth muscles like the small intestine)
  • 800mg Magnesium Citrate
  • Ginger tea
  • Meditation and yoga poses focused on the solar plexus and vagus nerve. From an emotional/ energy healing perspective this seems to be tied to anger issues and related to some stuck energy in my neck and shoulders.
  • Vagus nerve stimulation exercises like gargling and chanting.

Finally, the following are helping to manage the symptoms while I work on root cause:

  • My whole food, plant based ketogenic diet is already fairly low FODMAP but the GI consequences are a great motivation not to cheat with artificial sweeteners.
  • I temporarily stopped my daily probiotic, daily homemade saurkraut and other fermented foods, and reduced the pre-biotics in my diet. I can’t bring myself to give up garlic, though.
  • Senna tea, rarely as it can be habit forming, and a weekly Vitamin C flush has helped to keep a few things moving through.
  • Abdominal massage.
  • An incredibly patient husband whose world is currently a swirling cloud of my moans and farts.

I’ll do a whole post on it once it’s resolved.

Final Note

As awful as it is, I’m incredibly grateful to be able to experience SIBO and die-off first hand. I’ve had people report symptoms like rashes and body pain after a day or two of fasting. I’m now much more understanding that these are likely symptoms of a Herx reaction and know first hand how painful they can be.

I originally felt a little shame that, after 18 months of such immaculate eating and attention to my gut health, I could suffer from something like SIBO. I’ve since heard from some of the cleanest eaters and purist healers I know that they’ve experienced the same.

I understand now, too, that I was experiencing overgrowth last year while I battled diarrhea and bowel incontinence. Those are classic symptoms of hydrogen-dominant SIBO that I wrongly attributed to my meds. The hydrogen-releasing bacteria feed the methane-releasing bacteria and archaea. This explains my transition from uncontrollable diarrhea to constipation to my current point of complete bowel immobility.

Above all, I’m excited for the place where my body will be once I clear this infection. The gut-brain-immune system connection has been well established and I need healing in all three elements. Hopefully I have that and a post with my learnings in just a few months.

In the meantime, I’ll keep up my regular 2-3 day fasts and look forward to another long fast in the future.

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Amber October 1, 2020 - 2:43 am

Great info! I’ve read that Senna tea can cause dependency. You may want to look into it. Thanks for the article!

Maggie Jones October 1, 2020 - 7:16 am

It can indeed! It was a good crutch for a couple especially acute weeks. But not longer than that and not everyday. I should clarify for those who don’t know the risks. I don’t use it now except perhaps once every two months. Fortunately, the herbal antibiotics and biofilm disruptors really helped and regular enemas keep me comfortable. Thank you for pointing out the need to add a warning!

Diana October 7, 2020 - 11:33 am

Hello, Maggie, I left a comment in one of your other post last week. I am asking here the same question. When your GKI is below 1, what is your glucose and what is your ketone level? Iam asking because my glucose reaches very low valuess (hight 40s) afer ~24 h of fast. My ketones spike to 5 or 6 and I am fine, I do not have hypoglicemia symptoms. But I am curios if your glucose ever gets so low.

Secondly, couldn’t your SIBO be caused by prolonged use of doxycycline?

Maggie Jones October 7, 2020 - 3:46 pm

Hi Diana!

My last extended fast post has both blood glucose and ketone numbers: https://cancerv.me/2019/07/12/extended-fast-results-167-hours-of-nothing-exciting/

Generally my glucose is low 70swith my ketones around 5-6+. I’ve gotten down t the 40s early in my fasting days and, like you, because my ketones were high I felt great and was able to work out and be effective at the office. These days my blood glucose tends to be a bit higher due, I think, to my gastroparesis and adaptive glucose sparing.

And yes, I would not be surprised if my 3 month-long courses of doxy contributed to the SIBO although I know the root cause is lack of gut motility that correlates more strongly with my carmine deficiency and gastroparesis. In any case, it’s a drag but still infinitely better than dying of cancer

Sending you love! Maggie

Diana October 9, 2020 - 12:20 pm

Thank you so much, Maggie, for sharing! I will check the older post too. I am following your blog and I was so excited to see everything I’ve learned with so much effort and time summarized in such an articulate and concise way. People like you are changing the cancer treatment paradigm. Looking forward to future updates. Best wishes!

AJ May 21, 2021 - 6:07 pm

Hey dear –

For what it’s worth, it might help strengthening underneath to be able to fend off the infection and keep it away. This is what got me well: lots of D, A, C, zinc, a multimineral complex, strengthening stomach acid, thiamine, P5P, and animal foods. The animal foods were probably the biggest key! The SIBO is a topical sign of a weak immune system + often a metals problem. Good luck!

Karina July 1, 2021 - 4:01 am

Hey! Are you cured of SIBO now? I have methane too and it’s SOO hard to get rid of!

Maggie Jones July 1, 2021 - 4:31 am

Hi Karina!
Truth? I don’t think I’ll ever be cured. I’m lucky to be in good remission now but, except for a brief reprieve in August 2020, I haven’t taken a poop without an enema since March 2020 and even the tiniest hint of my trigger foods (sugar alcohols, nuts, carrots..) sets off crazy bloating. Still, avoiding those foods, regular morning enemas and periodic biofilm herbs makes things manageable. Overall, though? Way harder to kick than stage 4 cancer. Good luck!!

Kristen August 27, 2021 - 4:25 am

Can you please share your enema routine? I’m suffering from methane SIBO as well, and the only thing that was keeping me sane was weekly vitamin c flushes. But then I got a kidney stone, so I can’t do them any longer! Enemas don’t work for me. Are you using coffee? Any other enema tips? Thanks!

Maggie Jones August 27, 2021 - 9:58 pm

Oof! I’m so sorry for what you’re going through! I’ve been really grateful for finally finding a rhythm that keeps the worst of my bloating and pain under control. For the last 6 months or so I’ve been doing a daily morning enema using just reverse-osmosis filtered water or bottled before we installed the filtration system. First thing in the morning I fill a 2L bag with warm water (combo of the room temperature and boiled in the kettle), oil the insertion end and my pooper with coconut oil, lay on a towel and insert. These days I can transfer the whole 2L at once, then I massage my abdomen for a few minutes, put away the towel, wash the insertion tip, brush my teeth and do my other morning stuff before sitting on the toilet. It usually takes an average of around 20-30 minutes on the toilet clear out. Sometimes I’ll do a second 2L bag.

I still take regular biofilm disruptors and avoid my trigger foods. Adding this daily movement makes me feel almost normal. I really really miss pooping like a normal person, though. I just finished an experiment with the carnivore diet that hasn’t helped. With my enema routine able to flush out toxins, I’m ready to try the 14 day fast again. I’ll update this blog when I do!

Good luck to you!!

Kristen Park August 30, 2021 - 3:18 pm

Hi Maggie,

Thanks so much for your response!

I think it would work for me with 2L of water. Any less and I won’t go. I love the second bag idea too! I will keep this gem in my back pocket.

I just started taking high dose magnesium citrate this week. I started at 840mg with pretty good results. I went up 1260mg last night and it was too much, so I’ll dial it back. Hooray! I was prepared to go up past 2000mg per my naturopath, but it looks like I won’t have to.

I can’t take the biofilm disruptors or the herbs any longer because I’ll be doing IVF in November. So I’m going to into pregnancy with SIBO. 🙁 The IVF is time sensitive so I can’t put it off. But if I can keep regular with magnesium during pregnancy it will be a HUGE win!

My naturopath had said I just needed to keep going and going with the biofilm phase-2 advanced disruptor at large doses and the biocidin for SIBO, and it was in fact getting better before I had to stop due to the IVF. I had a terrible reaction to allicin and berberine (nausea and severe junk food cravings) and I immediately tested positive again for SIBO at the same levels after taking those herbs.

The Amy Myers’ AIP diet has worked for me (about 5 days in and my constipation is gone), as has drinking organic celery juice daily (something I’ll consider doing during pregnancy if needed). I also did the Metagenics 10 Day Cleanse a few years ago, and that diet worked for my constipation as well. But they were all a short term fix and none of those were sustainable for me.

Thanks again for sharing your story and providing us with great info! I’ll be keeping an eye out for your future posts.


Maggie Jones August 30, 2021 - 9:40 pm

Holy smokes! SIBO and pregnancy! I just can’t imagine. I really hope you keep things moving with the magnesium and am totally inspired me to try megadoses of magnesium citrate. I take a ton of magnesium in different forms (citrate, oxide, glycinate, taurate, l-threonate) but can’t believe I never though of just upping the citrate. I’m super excited to try!

I checked out the Metagenics cleanse but their drink contains sugar, which I can’t eat. Their diet is also already less restrictive than what I currently eat (past 3 years no sugar, no processed food, no alcohol, no seed oils, no dairy, no animal products except occasional pasture-raised egg and wild-caught salmon, limited legumes, limited fruit, etc).

Anyway, thank you so much for the awesome info! I really helps to compare notes with others who have been through the same thing. Sending you and your baby all my love!

Kristen Park August 31, 2021 - 8:17 pm

Yes, it’s going to be challenging! I have heard that often SIBO goes away during pregnancy, but I also just heard it can prevent you from becoming pregnant. So I’ll have to see how it goes! I’m going to take another round of herbs before IVF.

So far the magnesium is working! I hope the high doses work for you too.

This Autoimmune Protocol diet also worked for my constipation: https://goop-img.com/wp-content/uploads/2018/05/Foods-to-Enjoy-vs-Toss_The-Autoimmune-Cookbook.pdf.

But it wasn’t sustainable for me.

Thanks again for your post and responses! 🙂 It is so good to connect with people who have the same issue and to learn and heal from them.


Kristen September 17, 2021 - 7:06 pm

I wanted to share this great podcast I came across about SIBO and constipation from The SIBO Doctor. Most of the supplements they recommend I can’t buy or find online. But I am having a bit of luck with PHGG and I’m interested in trying the probiotics if I can find them:


Maggie Jones September 18, 2021 - 5:03 pm

Hi Kristen! You are so awesome – I can’t wait to check this out. I’ve been doing the 1200mg of Magnesium Citrate and, while nothing has moved yet, I *feel* like it might happen soon. Thank you so much for thinking of me and posterity even while you’re dealing with this nightmare. I hope you find permanent relief soon!

Kristen September 21, 2021 - 4:59 am

Thanks! Best of luck with the magnesium citrate. And thank you for enema idea, which I am doing now (with coffee)!

I look forward to reading about your success. 🙂

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