IBS and the keto diet

When Audra Atkins-Reeves started a keto diet in October 2016, her only aim was to lose weight. And within five months, she was happy to find that she’d lost 40 pounds (18 kg).

But the 36-year old IT supervisor from California also discovered another welcome, unexpected benefit from her new way of eating: it almost completely eliminated her long-standing irritable bowel syndrome (IBS).

Within a month of starting keto, her gut was remarkably calm, quiet, and cooperative for the first time in decades.

“Honestly, I’d never had a normal bowel movement for almost my whole life,” said Atkins-Reeves, who alternated between extreme constipation and diarrhea (referred to as IBS-C and IBS-D). Her doctor’s solution was to give her drugs for both, which she switched between.

Changing to a low-carb, high-fat diet completely resolved her constipation and reduced her formerly frequent attacks of diarrhea to less than once a month.1

“My ketogenic diet now completely controls my IBS symptoms,” she says. “And if I do ever cheat and indulge in some of my old triggers like ice cream or fruit, it doesn’t seem to cause an attack anymore. In the past, I would have been in the bathroom within an hour.”

Most of us are ecstatic to broadcast our keto successes with weight loss or reversing type 2 diabetes. We talk to friends and family enthusiastically about the pounds melting off, our blood sugar normalizing, and our minds becoming clearer. We post before-and-after pictures on Facebook and explain how eating meat, eggs, and butter is giving us a new lease on life.

But go into rapturous details about keto’s impact on our bowels? Not so much!

Talking frankly and honestly about gastrointestinal issues is squeamish stuff, the last taboo. It’s tough for some to share details about how a once-churning caldron of GI distress has quelled or painful constipation has eased, simply by switching to a low-carb diet.

Low-carb physicians share experiences from IBS patients

For many, relief from IBS comes as a welcome surprise. Improvements in symptoms are commonly reported in emails to Diet Doctor. Many keto-themed blogs discuss the phenomenon, as do Reddit discussion threads.2

A survey of doctors who recommend low-carb eating found that among their patients, it’s very common to have dramatic improvements or even resolution of long-standing IBS symptoms.3
It is one of the most appreciated side effects of the diet. Dr. Ted Naiman said he has seen it occur among “countless patients.” Dr. Sarah Hallberg also says, “We see it all the time.”

So has Dr. Andreas Eenfeldt. “I remember one male patient in his late 20s who had suffered crippling IBS symptoms for most of his life,” he said. “I suggested he try a low-carb, high-fat diet, gave him a one-page pamphlet, and he agreed to give it a try. It was a quick ten-minute consultation.

When I called him two weeks later, his GI symptoms were not only completely gone, but for the first time he could remember, he’d also lost a surprising amount of excess weight. And all without a single medication.”4

Dr. Evelyne Bourdua-Roy agrees. “It is super common,” she says. “Most patients have given up hope of getting treatment, it seems. They’ve tried a lot of stuff, they’ve had a colonoscopy, they’ve had tests for food intolerances and celiac disease — all with no answers.”

But when they go on a low-carb diet, most see an improvement within two weeks or less, she says.

In addition to most of Dr. Bourdua-Roy’s patients having improvement or complete disappearance of their IBS symptoms, she has experienced it herself. “I’ve had a complete resolution of bloating, pain and excessive gas.”5

I have, too. I now consider my mild IBS completely cured on the ketogenic diet. In my very first post for Diet Doctor, I described how going low carb resolved not only my prediabetes but resulted in barely a grumble from my sometimes grumpy gut.

Like Atkins-Reeves, it seems the diet has even reset my underlying intestinal tolerance. Trigger foods that used to bother me, like runny eggs or raw spinach, don’t give me trouble anymore.

Could restricting carbohydrates be the key to your happier gut?

Read on for more information about what is known, and not known, about IBS in general  — and when carbohydrate restriction might be just the solution to tame your tumultuous tummy.


1. IBS is very common and very disruptive

Between 10-20% of people worldwide are estimated to have IBS, and two-thirds of all cases are believed to occur in women.6
Studies suggest that more than 1 in 10 visits to family doctors — and at least 1 in 4 to gastroenterologists — are for IBS symptoms.7
It’s been shown to significantly reduce work productivity and lower quality of life.8
But do we talk about it much? Nope. Most people suffer in silence and many don’t even bring it up to their doctor.

Dr. Bourdua-Roy says that silence is very common among her patients. “Most of my new patients don’t even mention it. They’ve tried numerous modifications to their diet, so most think it’s useless to make another effort.”

The key defining symptoms of IBS are recurrent abdominal bloating, pain, diarrhea and/or constipation. Excessive flatulence, cramping, heartburn, nausea, vomiting, exhaustion, sweating, shivering, anal itching, and sudden incontinence can be part of the not-so-pretty picture, too.9

A few serious medical conditions can have symptoms similar to IBS: celiac disease, inflammatory bowel disease (Crohn’s and ulcerative colitis), and certain types of cancer, especially colon or ovarian cancer.

While these conditions are much less common than IBS, they should be ruled out before settling on an IBS diagnosis, international IBS guidelines say.10

The key factor that distinguishes IBS from other gastrointestinal issues is that diagnostic tests can’t find anything wrong. This is why it’s often called a “functional” disorder, meaning it is based on symptoms after other causes have been ruled out.11

The takeaway: If IBS is causing a lot of distress, especially if symptoms are new, have a doctor rule out other more serious health issues first. But if IBS is the eventual diagnosis, you’re not alone. And a low-carb, high-fat diet may very well help.


2. Subtle physiologic differences in IBS

For decades, IBS symptoms were often seen by the medical profession as largely psychosomatic — all in one’s head — which frequently caused sufferers to be labeled as neurotic, anxious, or depressed.12

Chronic stress is known to contribute to and worsen the disease.13 And anxiety and depression are often natural responses to a condition that can cause fear of public embarrassment or undermine quality of life — especially when the symptoms are dismissed as psychological by doctors.14

Research, however, is now pointing to a variety of subtle changes that may underlie the development of IBS.
These include an altered immune system, the presence of low-grade inflammation, the proliferation of nerve fibers in the intestinal wall, or pre-existing genetic susceptibility.15
The takeaway: While stress can make IBS worse, it is not all in your head. Impaired immune function, genetic predisposition, and physiological changes that haven’t been captured by diagnostic tests may be at play.


3. Restricting FODMAPs for IBS


Foods containing FODMAPs

In recent years the low-FODMAP diet has been getting a lot of research attention for its ability to improve IBS symptoms.16

FODMAP is an acronym for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. That unwieldy name describes types of short-chain carbohydrates found in many fruits, vegetables, legumes, grains, dairy products, and some processed foods.

What FODMAPs have in common is that they tend to ferment in the small intestine, causing gas and bloating. They are also poorly absorbed by the gut wall and cause fluid to remain in the intestinal space, which can lead to diarrhea in those with IBS-D.17

FODMAPs include fructose and fructans found in many fruits, vegetables and wheat products; lactose, a sugar found in milk and some dairy products; galactooligosaccharides (GOSs) found in beans and lentils; and sugar alcohols (polyols) such as the sweeteners sorbitol, xylitol and mannitol.18

In recent years, following a low-FODMAP diet — under the guidance of a registered dietitian — has gained acceptance as a first-line therapy for IBS.19Patients first eliminate all FODMAPs in their diet and then slowly reintroduce them to see which ones they can tolerate.

However, along with acknowledging low FODMAPs as an option, most specialists still also recommend more traditional advice for IBS: small meals, regular food intake and avoidance of coffee and fat.20

Yet many discussion threads on the low-FODMAP diet argue that it’s too rigid and difficult to figure out which of the more than 200 carb sources are “in” or “out.”

Dr. Ted Naiman notes that the general very low-carb diet is easier. “No carbs equals no fermentation equals no IBS. It is simple and it works great.”21

The takeaway: Ample evidence now exists that short-chain carbohydrates called FODMAPs can cause problems in people with IBS, but the intricacies of the diet are challenging. A low-carb diet is a simpler way to eliminate many of the common FODMAPs.


4. Research evidence for a very low-carbohydrate or ketogenic diet

In 2009 a team at the University of North Carolina that included Dr. Eric Westman examined a diet containing less than 20 grams of carbs a day for IBS.

During the study, 13 people with diarrhea-predominant IBS (IBS-D) started with a standard American diet for two weeks, then switched to a very low-carb diet for four weeks. At the end of the study 10 participants (77%) had significantly less abdominal pain and diarrhea, along with improved quality of life.22

“A very low-carb diet, or LCHF, is basically a low-FODMAP diet with even fewer carbs,” said Dr Westman.

In a recent study from New Zealand, people were randomly assigned to follow a diet providing either 5, 15 or 25% of calories from carbs. All three groups reached ketosis and reported resolution of their abdominal bloating and cramping.23 While this was not specifically an IBS study, it confirms that low-carb diets can improve GI symptoms.

And a randomized clinical trial now recruiting in Sweden will assign IBS patients to one of three diets for four weeks: a standard diet, a low-FODMAP diet, or a very low-carbohydrate diet.

The takeaway: Anecdotal evidence on carb restriction for IBS abounds, and low-carb physicians consistently see symptoms improve in their patients. Formal research is growing, and studies suggest improvement can occur within a few weeks of starting low carb.

“The fact is that you will know quickly whether this works for you,” says Dr. Bourdua-Roy. “Try it for two weeks; take the Diet Doctor challenge. You will get the answer!”

Anne Mullens



  1. A ketogenic diet for beginners
  2. "I feel the best I’ve felt for 25 years"
  3. A ketogenic diet for beginners - CTA test Draft

More on digestive issues

There’s one digestive issue that sometimes does not improve on keto, it may occasionally even get worse: constipation. If needed, use our guide below.

More on digestive issues, how they can be improved and stories about success

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IBS and the keto diet - the evidence

This guide is written by Anne Mullens and was last updated on June 17, 2022. It was medically reviewed by Dr. Bret Scher, MD on April 2, 2020.

The guide contains scientific references. You can find these in the notes throughout the text, and click the links to read the peer-reviewed scientific papers. When appropriate we include a grading of the strength of the evidence, with a link to our policy on this. Our evidence-based guides are updated at least once per year to reflect and reference the latest science on the topic.

All our evidence-based health guides are written or reviewed by medical doctors who are experts on the topic. To stay unbiased we show no ads, sell no physical products, and take no money from the industry. We're fully funded by the people, via an optional membership. Most information at Diet Doctor is free forever.

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Should you find any inaccuracy in this guide, please email andreas@dietdoctor.com.

  1. [anecdotal report; very weak evidence]

  2. [anecdotal report; very weak evidence]

  3. This is based on clinical experience of low-carb practitioners and was unanimously agreed upon by our low-carb expert panel. You can learn more about our panel here [weak evidence].

  4. [anecdotal report; very weak evidence]

  5. [anecdotal report; very weak evidence]

  6.  Clinical Epidemiology 2009: The epidemiology of irritable bowel syndrome [overview article; ungraded]

  7. Postgraduate Medical Journal 2003:Management of irritable bowel syndrome [overview article; ungraded]

  8. The British Journal of General Practice 2004:Systematic review: the economic impact of irritable bowel syndrome[systematic review of descriptive studies; ungraded]

    The American Journal of Managed Care 2005:Impairment in work productivity and health-related quality of life in patients with IBS[survey;ungraded]

  9. Journal of Clinical Medicine 2017:Rome criteria and a diagnostic approach to irritable bowel syndrome [overview article; ungraded]

    Neurogastroenterology & Motility 2017: Fecal incontinence in irritable bowel syndrome: Prevalence and associated factors in Swedish and American patients[observational study; weak evidence]

  10. Deutsches Arzteblatt International 2011: Irritable bowel syndrome – The main recommendations[overview article; ungraded]

  11. Deutsches Ärzteblatt International 2012: Functional bowel disorders in adults
    [overview article; ungraded]

  12. Gut 1987: Psychological factors in the irritable bowel syndrome [overview article; ungraded]

  13. Minerva Medica 2004: Psychological influences on the irritable bowel syndrome [overview article; ungraded]

    Behaviour Research and Therapy 1990: The role of anxiety and depression in the irritable bowel syndrome [observational retrospective study; very weak evidence]

  14. Current Psychiatry Reports 2004: The interface of psychiatry and irritable bowel syndrome [overview article; ungraded]

    Digestion 1999: Impact of irritable bowel syndrome on quality of life and resource use in the United States and United Kingdom [observational retrospective study; very weak evidence]

  15. Journal of Neurogastroenterology and Motility 2016: Mast cells and irritable bowel syndrome: from the bench to the bedside [overview article; ungraded]

    Current Gastroenterology Reports 2008: Is irritable bowel syndrome an inflammatory disorder? [overview article; ungraded]

    Gastroenterology 2015: Nerve fiber outgrowth is increased in the intestinal mucosa of patients with irritable bowel syndrome[case-control study; very weak evidence]

    World Journal of Gastroenterology 2015: Genetic epidemiology of irritable bowel syndrome [overview article; ungraded]

    BMJ Open Gastroenterology 2017: A Swedish national adoption study of risk of irritable bowel syndrome (IBS) [case-control study; very weak evidence]

  16. Gut 2021: Efficacy of a low FODMAP diet in irritable bowel syndrome: systematic review and network meta-analysis [strong evidence]

    Frontiers in Nutrition 2021: A low-FODMAP diet improves the global symptoms and bowel habits of adult IBS patients: a systematic review and meta-analysis [strong evidence]

    European Journal of Nutrition 2021: Efficacy of a low-FODMAP diet in adult irritable bowel syndrome: a systematic review and meta-analysis [strong evidence]

    Gastroenterology Nursing 2019: Effects of low-FODMAPS diet on irritable bowel syndrome symptoms and gut microbiome [strong evidence]

    European Journal of Nutrition 2016: Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta-analysis [review of randomized and non-randomized trials; moderate evidence]

  17. Therapeutic Advances in Gastroenterology 2012: Fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) and nonallergic food intolerance: FODMAPs or food chemicals? [overview article; ungraded]

  18. Current Gastroenterology Reports 2015: Dietary fructose intolerance, fructan intolerance and FODMAPs [overview article; ungraded]

  19. Journal of Gastroenterology and Hepatology 2017: The evidence base for efficacy of the low FODMAP diet in irritable bowel syndrome: is it ready for prime time as a first-line therapy? [review of randomized and observational trials; moderate evidence]

  20. Gastroenterology 2015: Diet low in FODMAPs reduces symptoms of irritable bowel syndrome as well as traditional dietary advice: a randomized controlled trial [moderate evidence]

  21. This is based on consistent clinical experience of low-carb practitioners. [weak evidence]

  22. Clinical Gastroenterology and Hepatology 2009: A very low-carbohydrate diet improves symptoms and quality of life in diarrhea-predominant irritable bowel syndrome [non-controlled study; weak evidence]

  23. Nutrition X 2019: The effect of differing levels of carbohydrate restriction on the achievement of nutritional ketosis, mood, and symptoms of carbohydrate withdrawal in healthy adults: A randomised clinical trial [moderate evidence]