Can Intermittent Fasting Help with Inflammatory Bowel Disease?

Intermittent fasting has become a popular approach to eating and you may be wondering what exactly intermittent fasting is. Intermittent fasting is an umbrella term that describes many different fasting cycles. Rather than focusing on what foods are eaten, it focuses more on when foods are eaten. In this blog post, we’ll explore some basics about intermittent fasting, review the research for intermittent fasting in inflammatory bowel diseases, and share some evidence-based benefits and risks.

Intermittent Fasting Basics 

There are many styles of intermittent fasting that differ depending on the rules during the fasting periods. Regardless of the style, fasting periods are generally a set amount of time where food or energy-containing drinks are avoided. Drinking water or other non-caloric beverages during fasting periods is usually allowed. There are 3 main styles of intermittent fasting:

  1. Alternate day fasting – Fasting for longer periods of time, such as 20-36 hours. This usually works out to fasting every other day. Small amounts of calorie containing foods may be included on fasting days.
  2. Time-restricted feeding – Fasting for a shorter period of time each day which limits the window of eating time. For example, fasting for 16 hours and then eating for 8 hours each day. For some this may look like skipping breakfast and eating between noon-8pm each day.
  3. Modified fasting regimes – Fasting for repeating and pre-scheduled periods of time. For example, fasting on Mondays and Thursdays each week.
  4. Fasting for religious purposes – Although this isn’t considered a style of intermittent fasting, some individuals may choose to fast on religious holidays such as Ramadan.

Research on Intermittent Fasting and IBD

Despite being a popular topic, the research on intermittent fasting and IBD in humans remains quite limited. Most of the studies have been done in animals which can be a helpful starting point, but these results don’t necessarily translate to humans.

  • In one study, mice with colitis were randomly divided into different intermittent fasting diets and control groups. The diets tested included alternate day fasting, time restricted feeding, and modified fasting (4 days of reduced intake in a two week period). Both the time restricted eating and modified fasting diets showed reduced inflammation in the gut and brain, improvements in the gut barrier, and an increase in anti-inflammatory related gut bacteria. Alternate day fasting showed potential harm and worsening disease, which was thought to be related to over restriction of calories and poor nutrition status.
  • Another study on mice with colitis compared a modified fasting diet (4 days of reduced intake in a two week period), a 2 day water only fast, and a standard diet. Overall, the modified fasting diet showed a superior reduction in markers of intestinal inflammation, promotion of protective gut bacteria, and increased intestinal cell repair compared to the 2 day water fast and standard diet. Additionally, a fecal transplant from the fasting mice to the mice on a standard diet showed improvements in IBD symptoms.
  • Another study compared mice with colitis that fasted for 36 hours with a non-fasting group. The results suggest that intermittent fasting led to better recovery of intestinal cells and reduced general inflammation. Interestingly, this study highlights that the food eaten after fasting may also impact intestinal health.
  • The only human study that was found was a study on 60 participants with IBD who fasted for Ramadan. This observational study measured quality of life, psychological state and disease severity before and after Ramadan. However, the results suggest that there was no correlation between fasting and these variables.

This research is certainly exciting, but we need more studies done on humans to help us better understand the potential impacts of intermittent fasting on both Crohn’s and ulcerative colitis.

Potential Benefits and Risks

One theory behind the potential benefits of intermittent fasting is that it can lead to changes in your gut bacteria to help support an anti-inflammatory environment in the intestines and restore the gut barrier. It is important to know however, that achieving these benefits is less about the timing of eating, but rather an overall reduction in the amount of food being eaten. So, for those who are looking for a structured approach to eating, intermittent fasting may be a helpful way to limit excess food. However, we also know that there are other ways to support our gut bacteria without the need to fast. Eating a wide variety of whole grains, fruits, and vegetables during periods of remission can help feed our gut microbiome and achieve similar results.

One downside to intermittent fasting is that it isn’t a way of eating that’s suitable for everyone. Patients with IBD are often malnourished, are at risk for nutrient deficiencies, and can be on medications with complex interactions. Since fasting is often used as an approach to limit dietary intake, it’s likely not an approach desired for most living with IBD. This is because fasting can lead to further weight loss and inadequate intake by adding more restrictions to eating. Additionally, intermittent fasting isn’t recommended for those with a history of disordered eating, those who are pregnant or breastfeeding, or those who need regular intakes of foods, such as for medications or in type 1 diabetes.

A final potential risk is that those who have engaged in intermittent fasting have reported heightened irritability, increased fatigue, difficulty concentrating, and a loss of control or over-eating during non-fasting periods. For those with sensitive stomachs or intestinal tracts as in IBD, a big burst of food from overeating can lead to increased abdominal cramping, bloating, and uncomfortable gas or bowel movements. Rather than restricting and potentially overeating, eating slowly and having smaller but more consistent meals and snacks throughout the day is recommended.

Intermittent fasting may certainly work for some people, but it appears that there isn’t enough evidence to recommend it for the IBD population at this time.

Take-away Points

  • Intermittent might help some reduce their overall dietary intake
  • Intermittent fasting and dietary choices in general can impact our gut microbiome
  • There is insufficient evidence to say that intermittent fasting can help improve inflammation or symptoms in humans with IBD
  • Intermittent fasting is not appropriate for those who are malnourished and may lead to further nutrient deficiencies or weight loss


Author: Sophia Jhajj, 5th year dietetics student

Reviewed and edited by: Kaity McLaughlin, MPH RD, and Gina Almasan, RD


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