Is Fasting Good for IBS?

Posted in: Gut Health

IBS Specialists as featured in the Guardian

5th February 2024

By Victoria Tyler



  • Is Fasting good for IBS?
  • What is Fasting?
  • Why do I feel better when I fast?
  • Is fasting good for an IBS flare?
  • Does fasting promote Autophagy?
  • Migrating Motor Complex and Intermittent Fasting
  • Fasting may help SIBO
  • What is MMC?
  • Fasting and inflammation
  • Is Fasting good for constipation?
  • Is Fasting good for Diarrhea?
  • Who should not fast
  • Summary

Is Fasting good for IBS?

Many of the patients we see at our clinic suffer from IBS and a common question we often get asked is whether Intermittent fasting is helpful to reduce symptoms of IBS. Unfortunately limited research exists in this area.

Many patients describe feeling worse after eating and develop symptoms including fatigue, bloating windy, and gas. Consequently, they instinctively gravitate towards avoiding meals as a means to better cope with and alleviate their IBS symptoms.

Before we answer the question of whether fasting is helpul for IBS, let’s first explain what fasting is.

What is Fasting?

There are various approaches to intermittent fasting, all centered around selecting specific time frames for eating and fasting. For example, one method involves eating only within an eight-hour window each day and fasting for the remaining hours. Alternatively, you could opt for consuming just one meal a day on two specific days of the week. The possibilities for intermittent fasting schedules are diverse.

Among the most widely adopted fasting techniques are:

16/8 Diet Intermittent fasting

Regarded by many as one of the most sustainable approaches to intermittent fasting (IF), the 16/8 method entails fasting for 16 hours and allocating an 8-hour window for consumption. The 16/8 window can be flexibly adjusted to encompass 14-16 hours of fasting and 8-10 hours of eating.

5:2 Diet

Participants eat normally for five days a week and significantly reduce calorie intake (around 500-600 calories) on two non-consecutive days.

Why do I feel better when I fast?

It doesn’t really matter what type of fasting method you undertake but the avoidance of trigger foods may temporarily decrease your symptoms of IBS.

If you fast you may experience a decrease in your digestive symptoms due to the removal of trigger foods. However this benefit may be temporary as when you resume eating foods, at some point symptoms are likely to return.

Fasting essentially acts as a temporary pause on your regular eating habits. It gives your digestive system a break from potential troublemakers. While it’s reasonable to expect a reprieve from IBS symptoms during this fasting period, the challenge arises when you reintroduce your usual foods – the triggers that may reignite those symptoms.

Imagine that you have an intolerance to lactose, a common trigger for IBS symptoms. Opting for a fasting period, where you abstain from lactose-containing foods for at least 12 hours, might indeed lead to a noticeable decrease in symptoms. The logic is straightforward – avoid the triggers, avoid the symptoms. Yet, there’s a critical caveat: this relief is often short-lived.

Unfortunately fasting doesn’t address the root causes of IBS. It serves as a brief solution, offering momentary relief until the consumption of the trigger food is resumed.

Fasting and IBS

Other reasons why fasting may help with IBS include:

  1. For some people, abstaining from food, will give them a feeling of control and reduce stress and anxiety. By avoiding food, they will be reassured that symptoms will not flare up.
  2. Many patients actually have underlying foods intolerance and so by removing the offending foods, they will feel better.

Is fasting good for an IBS Flare?

When you fast, you give your digestive system a break because you’re not eating as much. For some people with IBS, taking this break from constant digestion, can help reduce symptoms such as bloating gas and stomach discomfort.

However, this is not a one-size-fits-all solution, and individual responses may vary.

Introducing structured fasting periods may also encourage healthier eating habits. For instance, it may discourage you from overeating or consuming trigger foods, common contributors to IBS symptoms

Does Fasting promote autophagy?

Have you heard of autophagy? Autophagy is a term derived from Greek meaning “self-eating.”

Intermittent fasting, has been associated with promoting autophagy. This strategy allows the body to experience periods of nutrient deprivation, prompting cells to initiate the autophagic process. This is a beneficial respite for the gastrointestinal tract, allowing it to unwind and engage in essential self-repair during periods of abstaining from food. By refraining from snacking and continuous grazing every few hours, the digestive system is spared the continual burden of processing, providing relief for those prone to abdominal discomfort and bloating due to frequent eating intervals.

Fasting may help IBS if you have SIBO

One of the underlying causes of IBS may be linked to a condition known as SIBO, Small intestinal Bacterial overgrowth. In this case, fasting may alleviate some symptoms of IBS as it will stimulate the migrating motor complex.

Small Intestinal Bacterial overgrowth is a condition where patients have an excess quantity of bacteria in the small intestine.

Dr Pimentel and Dr. Siebecker talk a lot about impaired MMC, migrating motor complex as  an underlying cause of SIBO.

But what is the MMC?

The migrating motor complex is a cleansing wave that flushes out bacteria from the small intestine at regular intervals throughout the day. When we fast for at least four hours this cleansing wave is stimulated and should help us get rid of bacteria. This should then have a knock on effect of helping us feel lighter, less bloated and less windy.

If your IBS is caused by an overgrowth of bacteria in the small intestine then you may find that fasting can stimulate the MMC thereby improving gastrointestinal motility allowing bacteria and intestinal contents to be swept through the GI tract, giving you some relief.

The bottom line, fasting  may help with IBS because when we fast, we stimulate the migrating motor complex.

Fasting decreases Inflammation

Fasting has also been associated with a decrease in inflammation markers in the body.

Since inflammation can contribute to symptoms of IBS, this anti-inflammatory effect may be beneficial for individuals with IBS.


Why fasting may not help IBS-C constipation

Even if fasting temporarily receives symptoms of IBS, it may not be the best choice for everyone, and it’s crucial to exercise caution or avoid it in specific circumstances. Consider refraining from fasting if you suffer from constipation or IBS-C.

When we fast, out gut motility may slow down as out gastrocolic response is not stimulated following a meal. This reflex is responsible for the urge to have a bowel movement by means of migrating contractions or migrating motor complexes following food entering the small intestine.

If you suffer from constipation it is important to consume a balanced diet rich in fiber, stay adequately hydrated, and incorporate foods with natural laxative properties, such as fruits, vegetables, and whole grains. Additionally, maintaining regular meal times may contribute to a healthy digestive system.

Does fasting help IBS -D diarrhoea?

Adopting a fasting approach may provide your body with a respite from potential food triggers and allergens, allowing your digestive system to take a break. These factors may result in a temporary reduction in the occurrence of diarrhea associated with irritable bowel syndrome.

Who should avoid intermittent fasting?

It is important to note that fasting is not suitable for everybody, particularly for patients who experience pain and discomfort on an empty stomach.

Patients who are also malnourished or underweight should avoid fasting due to the restriction of calories.


  • There is limited research to support fasting for IBS.
  • Fasting may temporarily relieve symptoms of IBS due to removal of trigger foods, allergens and gives your digestive system a break.
  • Fasting may help IBS if you have SIBO as it will stimulate the migrating motor complex.
  • Fasting may not be indicated if you have IBS -C constipation

Victoria Tyler is a UK registered Nutritional Therapist and member of the British Association of Nutritional therapy. She was awarded UK BSc Honours Degree in Nutritional Therapy and has trained in GI Functional Medicine. Victoria has been working with Gut disorders since 2004 after first experiencing digestive problems herself. She felt that the NHS was unable to provide the support individuals needed and went on to specialise in this area before offer bespoke IBS service.


Booking an appointment

If you need help with digestive symptoms please contact us and we would be pleased to book you in for a consultation at our IBS clinic