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Fasting and IBS: A Helpful or Harmful Strategy?

I’ve mentioned before that sometimes a little bit of fasting can help me recover from an IBS flare, but it seems fasting can also aggravate my IBS if done too long or not properly.

When is fasting helpful for IBS?

For instance, if I have a bout of diarrhea after dinner, the best thing to do is to not eat or snack on anything else for the rest of the evening and wait until the next morning. I may then also at relatively light the next morning as well until I am feeling much better. Of course, this isn’t necessarily really fasting since I don’t usually eat anything after dinner anyway for the rest of a given evening. I do find if I am having a bout of diarrhea, that it’s best to abstain from eating for at least a few hours and when I do eat, do it very modestly and stick to comparatively “safe” foods. Sometimes the stomach needs a break.

When is fasting harmful for IBS?

However, on the other hand, in general, I find that one of my mainline defenses is sticking to an eating routine. That means I need to eat my main meals around the same time every day and stick to certain staples. And for many others with IBS, adhering strictly to a meal schedule is crucial in managing their condition. And fasting would fly in the face of that.

So, if I am feeling relatively okay, and not in the midst of an active flare, there’s really no reason to fast because I will wind up probably hurting myself more than helping my IBS.

Fasting and constipation

Yet, it is true that abstaining from food has helped me not just when I am having diarrhea but constipation. When I first graduated from college and into my very early 20s, I alternated diarrhea with very bad and painful constipation. Desperate to move things along, I would keep eating as well as drinking lots of coffee. But all it did was make me feel more bloated (my belly would become super distended!) with no relief until I finally would bring on a bout of diarrhea and then the cycle would repeat itself.

Finally, I realized I should just stop stuffing myself so much when I was feeling constipated and lay off the food and instead just drink a lot of water (I finally gave up coffee, realizing it was a big part of the problem!). If I did eat, I ate very light so as not to add too much to my already full digestive system. I actually found this seemed to help me a lot better and move things along and I would be able to go to the bathroom normally.

What does research say about fasting and IBS?

I tried to see if there were any scientific studies on fasting for IBS. I found just one, published in 2006 of 84 patients with IBS, 36 of which underwent a fasting regimen. The research revealed that fasting therapy “improved 7 out of the 10 symptoms they assessed” including abdominal pain and discomfort, abdominal distension, diarrhea and interference with life activities. Overall the study concluded that fasting therapy “may have beneficial effects on intractable patients with IBS.” 1

Of course, this is just one study with a small pool of participants, so its conclusion should be taken with a grain of salt. As with everything, one should consult a medical professional before trying a new regimen, including fasting. Other medical conditions and individual details should be taken into consideration also before undergoing anything new with diet. For instance, I have very low blood pressure and blood sugar issues. So going more than a half-day without eating would cause me to get very lightheaded and dizzy.

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

  1. Kanazawa M, Fukudo S. Effects of fasting therapy on irritable bowel syndrome. Int J Behav Med. 2006;13(3):214-20


  • ExplodingGuts
    6 months ago

    Am currently experimenting with fasting – long periods of the day without eating – to see if it makes any difference in the explosions of diarrhea. Not really. But I am thinning a bit, which is good since I can’t exercise as I would like to b/c exercise prompts explosions. I try to walk at the beach where there are public washrooms until I can get more reliable control of the guts. Frankly, I don’t notice any difference. I seem to need about 3 Immodiums every three or four days – sometimes 5-7. I’d like to be able to exclude them altogether but stomach says no, not yet.

  • Kelly Dabel, RD moderator
    6 months ago

    Thanks for sharing your experience. Good for you trying different strategies to find relief. How long have you been experimenting with fasting? What changes have you made to the foods you’re choosing. Wishing you relief ahead. Best, Kelly,

  • coxapple
    7 months ago

    Try this for a no risk option. Might you have too much roughage for your current condtion. Try three days or so with more with no roughage. Why do I know this can have an effect. Well I had IBS with C Diff and that diet had an amazing effect . Did I invent the diet? No, it is what you have to do… before a colonoscopy!! No doubt pre-colonoscopy preprs vary round the world. This was in the UK. Now it may be the case that it only has dramtic effects ( for those with looser habit) if you have C Diff, but I can’t imagine it will harm you if t you try it for a short time…bit like an od style Big Mac diet.

  • tmholland moderator
    7 months ago


    Thank you for sharing your experiences and am happy you found something that works for you. Hopefully folks will include their doctor in the conversation before trying anything new. Your contributions are appreciated and you help make this community what it is. Hope you are well today. -Todd, Team

  • cecilebelz611
    7 months ago

    I tried fasting but by the end of the day I am weak and just feel lousy.

  • Chris Hall moderator
    7 months ago

    Completely understandable, @cecilebelz611. Hope you’re doing well today. – Chris, Team

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