While some people may experience relief from IBS symptoms by fasting, more research is needed to confirm whether it’s effective.

According to estimates in the research, up to 12% of people in the United States live with irritable bowel syndrome (IBS).

While the exact cause of IBS is unknown, the symptoms of abdominal discomfort, intermittent abdominal pain, diarrhea, constipation, bloating, and gas are common if you have this gastrointestinal (GI) disorder.

Because IBS symptoms can interfere with daily life and can also be unpredictable, many people may wonder whether lifestyle modifications such as fasting can help manage IBS. A lifestyle modification is a limited change you make to your habits.

One lifestyle modification that sometimes comes up when discussing IBS is fasting. The two forms of fasting related to IBS management are intermittent fasting and long-term fasting.

With intermittent fasting, you alternate between periods of eating and periods of not eating.

One popular method of intermittent fasting involves restricting your eating to an 8-hour block of time. For example, your food consumption would happen between 1:00 p.m. and 9:00 p.m.

Long-term fasting involves restricting food and possibly fluids for an extended period of time (that is, 24 to 72 hours).

According to Ryan Warren, RD, a nutritionist at NewYork-Presbyterian Hospital and Weill Cornell Medicine, the benefit or lack of benefit from fasting for IBS greatly depends on the type of IBS as well as the cause of IBS.

“Patients who suffer from IBS experience a wide array of symptoms due to a variety of underlying etiologies [causes],” Warren said. “This must always be taken into consideration before making clinical recommendations.”

However, the research on fasting as a way to manage IBS is minimal. More studies are needed to really know whether fasting positively affects IBS.

What’s the migrating motor complex, and how is it related to fasting with IBS?

The migrating motor complex (MMC) is a distinct pattern of activity observed in GI smooth muscle during the times between meals, like periods of fasting.

Warren says to think of it as three phases of natural “cleansing waves” in the upper GI tract that occur every 90 minutes between meals and snacks.

It’s these phases that some people say contribute to the positive effects of fasting with IBS. But while there’s plenty of research on the MMC itself, there’s very little to no scientific evidence to support its role in reducing the symptoms of IBS.

Why fasting might improve IBS

If your symptoms — such as gas, bloating, or diarrhea — occur as a response to eating, Warren says that longer fasting periods (or structured meal spacing) may be useful for symptom management.

That’s because fasting patterns can help the MMC mechanism become more active and effective. Warren says that this can improve certain IBS symptoms, particularly when IBS is or may be caused by an overgrowth of bacteria in the small intestine.

Studies show that suboptimal [less than ideal] MMC function is correlated with small intestinal bacterial overgrowth (SIBO), which can often be a root cause of IBS,” Warren explained.

“Fasting patterns can improve gastrointestinal motility [ability of GI tract to move food] associated with the MMC, which allows intestinal contents to move efficiently through the GI tract,” she added.

This optimal motility is significant, Warren says, because it helps reduce the occurrence of SIBO and excess fermentation of food contents that may ultimately trigger IBS symptoms.

“Fasting is also linked to anti-inflammatory, gut-healing benefits through its proposed activation of autophagy (a natural process by which damaged cells degrade and rejuvenate themselves),” Warren said. This, in turn, may have positive effects on IBS symptoms.

Additionally, Warren says fasting may be linked to favorable alterations in the gut microbiota. “Maintaining a properly balanced gut microbiota (i.e., with a diverse range of beneficial species) is paramount in managing IBS,” she added.

According to Warren, fasting may nothelp IBS in cases in which long periods of fasting ultimately lead to the consumption of larger portions of food at the end of the fast.

“Excess volume of food contents in the upper GI tract can trigger symptoms in some individuals,” Warren said. “Fasting, therefore, may significantly backfire if it becomes a justification for excess intake later on in the day.”

Warren says that in her work with patients who exhibit certain kinds of gut hypersensitivity, hunger sensations or lack of food can be a trigger.

She explains that certain IBS symptoms can occur in response to the stomach being empty in these individuals. Symptoms can include:

  • pain
  • cramping
  • nausea
  • stomach rumbling
  • acid reflux

“For these patients, small, frequent meals may be recommended as an alternative to structured meal spacing or long fasting periods,” Warren said.

Since the research and scientific evidence on fasting is scarce, it’s important to look at other ways to treat IBS.

But there are several lifestyle modifications as well as medications to consider that can treat IBS symptoms.

Diet modifications

One of the first places to start managing IBS is your diet. Identifying and avoiding trigger foods is key to managing symptoms.

Depending on the severity of your symptoms, this may include foods with gluten and a type of carbohydrate called FODMAPs. Foods high in FODMAPs include certain fruits and veggies, dairy products, grains, and beverages.

Eating smaller meals at regular times is also a common suggestion, which contradicts the idea of fasting. That said, there’s more research on eating regular meals than there is on fasting.

A doctor may also recommend increasing your intake of fiber and upping your fluids.

Physical activity and stress reduction

Participating in regular exercise and physical activities you enjoy can help reduce stress, which helps with IBS symptoms.

You can also reduce stress and improve symptoms by practicing activities such as deep breathing, relaxation, and meditation can help you relax your muscles and reduce stress. Some people also find success with talk therapy for managing stress levels.


Probiotics are over-the-counter (OTC) supplements a doctor may recommend to restore helpful gut bacteria.

The idea behind probiotics is that you can introduce live bacteria into your system to enhance your health. Talk with a doctor about which probiotic supplement and dosage would be best for you.


A doctor may prescribe a medication to help with IBS. Some of the more common medications can:

  • relax the colon
  • ease diarrhea
  • help you pass stools more easily
  • prevent bacterial overgrowth

A doctor will first review your health history and symptoms. They’ll want to rule out any other conditions before moving forward.

If there are no concerns about other health issues, the doctor may recommend testing for gluten intolerance, especially if you’re experiencing diarrhea.

After these initial screenings, the doctor may use specific criteria to diagnose IBS. These include the Rome criteria, which assess things like abdominal pain and pain levels when passing stool.

A doctor may also request blood work, a stool culture, or a colonoscopy.

Although there are many theories about the cause, there’s no certain answer. That said, experts continue to look at contributing factors, including:

  • severe infections
  • changes in gut bacteria
  • inflammation in the intestines
  • overly sensitive colon
  • poorly coordinated signals between the brain and intestines

Additionally, according to the International Foundation for Gastrointestinal Disorders, certain lifestyle factors can trigger IBS, such as:

  • the foods you eat
  • an increase in your level of stress
  • hormonal changes that accompany the menstrual cycle

While the severity of symptoms can vary, there are a few common symptoms to look for when identifying IBS:

  • pain in the abdomen
  • changes in bowel movements
  • diarrhea or constipation (and sometimes both)
  • bloating
  • feeling like you haven’t finished a bowel movement

Does fasting help with bloating?

Fasting may not help with bloating. Studies suggest that fasting may actually cause symptoms like bloating in some people.

Can you use fasting to cure constipation?

Research suggests that some types of fasting, like alternate day fasting, may actually cause constipation in some people. Constipation can occur due to changes to how much a person eats. Fasting may also mean a person isn’t eating enough fiber, which can contribute to constipation.

Is fasting safe?

Eating for a 12-hour period and then fasting for a 12-hour period is likely safe for most people. Fasting can bring many health benefits, but not everyone can fast. It’s a good idea to speak with a healthcare professional before deciding to fast. This is especially important for people who:

  • are pregnant
  • are breastfeeding
  • are under 25 years old
  • take insulin or other diabetes medication
  • take medications that require food
  • operate heavy machinery
  • work night shifts
  • have a disorder that causes seizures

While some people are finding relief from IBS symptoms by fasting, the research and scientific evidence is minimal. More studies are needed.

If you’re considering fasting, consult with a doctor or a registered dietitian. They can help you decide if this is the right approach for you.