IBS and the keto diet

When Audra Atkins-Reeves started the low-carb keto diet in October 2016, her only aim was to lose weight — and happily she found within five months she had lost 40 lbs (18 kg).

The 36-year old IT supervisor in California, however, discovered another welcome, unexpected benefit from her new way of eating: it almost completely eliminated her long-standing irritable bowel syndrome. Within a month of starting the keto diet her gut was remarkably calm, quiet, and cooperative for the first time in decades.

“Honestly, I’d never had a normal bowel movement almost my whole life,” said Atkins-Reeves, who alternated between extreme constipation and diarrhea (called 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.

“My ketogenic diet now completely controls my IBS symptoms,” she says, noting that it even seems to have healed her gut’s old problems. “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 any more. In the past I would have been in the bathroom within an hour.”1

Most of us are ecstatic to broadcast our success with weight loss or reversal of type 2 diabetes on the keto diet. We talk to friends and family enthusiastically about the pounds melting off, our blood sugar normalizing, our cravings gone and our minds becoming beautifully clear. We post our before-and-after pictures on Facebook and detail how now eating meat, cheese, eggs and butter is giving us a new lease on life.

But go into rapturous details about keto’s impact on one’s bowels? Not so much! Talking frankly and honestly about gastrointestinal issues is squeamish stuff, the last taboo. It’s tough for some to share the particulars of how a once-churning caldron of GI distress has quelled or the bloated pain of constipation eased, all by switching to a very low-carbohydrate diet.


And yet, for many it is a welcome, surprising benefit. Improvements in IBS symptoms are commonly reported in emails to Diet Doctor. Many keto themed blogs discuss the phenomenon as do multiple Reddit discussion threads.2

A survey of doctors on this site, who recommend low-carb/keto eating, found that among their patients, it is very common to have a dramatic improvement, even a resolution of long-standing IBS symptoms.3It is one of the most welcome side effects of the diet. Dr. Ted Naiman said he has seen it occur among “countless patients.” Dr. Sarah Hallberg, too, 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 and 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, 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. Most patients have given up hopes of getting a treatment, it seems. They’ve tried a lot of stuff, they have had a colonoscopy, they have had tests for food intolerances and celiac disease with no answers.”

But when they go on the low-carb high-fat (LCHF) diet, most see an improvement within two weeks or less, she says. Not only does Dr. Bourdua-Roy’s have the majority of her patients on the diet report significant improvement or a complete disappearance of their IBS symptoms, she has experienced it herself. “I have 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 pre-diabetes, but resulted in barely a grumble from my sometimes grumpy gut. Like Atkins-Reeves, too, 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 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

At least 15 per cent of the general population are estimated to suffer from IBS — typically twice as many women as men. That means some 75 million people in Europe and 48 million in the US are affected. Studies show that more than one in ten visits to family doctors and at least one in four to gastroenterologists are for IBS symptoms. It is second only to colds for missed days at work.6

But do we talk about it a lot? Nope. Most 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 have tried numerous modifications to their diet so most think it is 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.7

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 in which new GI symptoms come on rapidly, especially at a later age. While all are much rarer than IBS, these conditions should be ruled out before settling on the IBS diagnosis, international IBS guidelines say.8

The key factor that distinguishes IBS from other gastrointestinal issues is that diagnostic tests can’t find anything wrong – that is why it is often called a “functional” disorder, meaning it is based on symptoms after other causes have been ruled out.9

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


2. Subtle physiologic differences now being found

For years, because nothing aberrant could be found on colonoscopies or other diagnostic tests, doctors dismissed IBS and offered little help to patients. That may be one main reason why so many people with the symptoms keep quiet about it.

In fact, for decades IBS symptoms were often seen by the medical profession as largely psychosomatic — all in one’s head — which often caused those who suffered to be labelled as neurotic or as having psychiatric precursors, particularly anxiety and depression. Chronic stress is known to contribute to, and worsen, the disease; 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 still too many doctors.10

Research, however, is now pointing to a variety of subtle changes that each may underlie the development of IBS, such as an altered immune system, the presence of low-grade inflammation, the proliferation of nerve fibres in the intestinal wall or pre-existing genetic susceptibility.11

The takeaway: While stress can make IBS worse, it is not all in your head; genetic susceptibility and micro-organic changes, hitherto undetected by diagnostic tests, may be at play. If your doctor gives you the old “nervous temperament” explanation for your symptoms, consider getting a second opinion– and try cutting carbs.


3. FODMAPs: research shows cutting out short chain carbohydrates improves symptoms


Foods containing FODMAPs

In recent years a specific diet developed in Australia, called the low FODMAP diet, has been getting a lot of research attention, with some studies showing 75 per cent of people with diagnosed IBS had their symptoms improve on it. FODMAP is an acronym for fermentable oligosaccharides, disaccharides, monosaccharide’s and polyols. That unwieldy name describes types of short chain carbohydrates found in many fruits, vegetables, legumes, grains, dairy products and some processed foods.12

FODMAPs are all carbs, and what they all 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, leading to diarrhea in those susceptible to IBS.

High FODMAPS include fructose and fructans found in many fruits, vegetables and wheat products; lactose, a sugar found in milk and some, but not all, dairy products; galactooligosaccharides (GOSs) found in beans and lentils; and sugar alcohols (polyols) such as the artificial sweeteners sorbitol, xylitol and mannitol.13

Eating a low FODMAP diet has in the last few years become the front line therapy for IBS, in which patients usually work with a dietitian to first eliminate all FODMAPs in their diet and then slowly reintroduce them, one-by-one back into their meals to see which they can tolerate and which they cannot.14

More than 200 FODMAP studies now exist, with the majority showing improved symptoms for more than 75% of patients. However, most IBS specialists still also recommend, alongside low FODMAPs, the traditional diet recommended for years, which stresses small meals, regular food intake and avoidance of coffee and fat.15

Many patient discussion threads on the low FODMAP diet, however, call it difficult to follow, rigid, and depressing to figure out the more than 200 carbs that 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.”

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


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

In 2009 a US team at the University of North Carolina, that included Dr. Eric Westman, specifically examined a very low-carb diet — less than 20g of carbs a day — for IBS. During the study, 13 people with diarrhea-predominant IBS started with a standard American diet for two weeks, then switched to a very low-carb diet for four weeks; 10 out of the 13 subjects (77%) had significant improvements, with the very low-carb diet improving their abdominal pain, reducing their diarrhea and improving their quality of life.16

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

Another study from New Zealand followed three different low-carb diets (5, 15 and 25% or calories from carbs) and found all three groups reached ketosis and reported resolution of their abdominal bloating and cramping.17 While this was not specifically an IBS study, it confirms the improved GI symptoms with low-carb diets.

Currently a randomized clinical trial is recruiting in Sweden that will assign patients to one of three diets for four weeks: standard diet, a low FODMAP diet, and a very low-carbohydrate diet.18

The takeaway: Anecdotal evidence abounds and low-carb physicians constantly see IBS symptom improvement; formal research evidence is growing. Most people, if they are going to have IBS improvements on a low-carb ketogenic diet, see it within two to four weeks.

“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!”

If you have experienced improvement in your IBS symptoms with the LCHF or ketogenic diet, let us know in the comments.

Anne Mullens


Top posts and guides about keto

  1. A ketogenic diet for beginners
  2. 14-day keto diet meal plan with recipes and shopping lists
  3. "I'm still hungry on a keto diet!"

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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  • Slipping and recovering on the keto journey
  • Is keto right for you? In two weeks, you'll know

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  1. 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].

  2. Current Gastroenterology Reports: Dietary fructose intolerance, fructan intolerance and FODMAPs

  3. Journal of Gastroenterology and Hepatology: 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?

  4. Gastroenterology: Diet low in FODMAPs reduces symptoms of irritable bowel syndrome as well as traditional dietary advice: a randomized controlled trial

  5. Clinical Gastroenterology and Hepatology: A very low-carbohydrate diet improves symptoms and quality of life in diarrhea-predominant irritable bowel syndrome

  6. 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]

  7. Clinicaltrials.gov: A comparison of three different treatment options for irritable bowel syndrome (Car-IBS)