Can fasting help IBD?

What the evidence says and how to do it safely

By Jude Bentley

Fasting is a topic that often comes up with my clients. When you’re living with inflammatory bowel disease (IBD), whether Crohn’s or ulcerative colitis, it’s natural to wonder if giving your digestive system a break might help. Could fasting be harmful, or is there something in it that genuinely helps calm inflammation and support healing?

This blog explores the research behind fasting and IBD, the difference a single day of digestive rest might make, and how to approach fasting in a safe, supportive way if you’re thinking about giving it a try.

What the research says about fasting and IBD

There’s growing interest in how intermittent fasting and short-term fasts might affect gut health. While human research is still in the early stages, animal studies and early trials suggest that a short period without food may offer some benefits for people with inflammatory conditions.

For people with IBD, fasting may:

• Reduce pro-inflammatory cytokines, including TNF-alpha and IL-6, both of which are often elevated in active disease
• Trigger autophagy, the body’s natural cell-recycling and clean-up process, which may help repair damaged intestinal cells
• Help regulate immune responses and reduce immune overactivation
• Support intestinal stem cell regeneration, which is key to healing the gut lining
• Temporarily reduce gut permeability, which is associated with symptoms and flare-ups

Some clients report that fasting for just one day helps them feel less inflamed, less bloated and more in control of their digestion. They often describe it as a reset after eating food that didn’t suit them or during times of stress when symptoms are more likely to be triggered. 

Do you need to fast for several days?

No. You don’t need to commit to a prolonged fast to see benefit. A single day of fasting may be enough to create a window for your gut to rest. Some people prefer a gentler version such as a 16-hour overnight fast, finishing dinner by 6pm and eating again around 10am the next day. (Night time eating is best avoided if possible when you have IBD because inflammation is higher at night.)

This type of short fast can still allow important processes to begin, including cellular repair and shifts in immune function. The aim is to reduce the digestive workload for a short time, not to deprive the body.

Who might benefit from a gentle fast?

A one-day fast or digestive rest period might be worth exploring if:

• You are in remission or experiencing mild symptoms
• You’ve eaten more heavily or more processed foods than usual and feel your digestion is sluggish
• You are interested in experimenting with time-restricted eating to see how your body responds
• Some people find it useful at the first sign of a flare or as part of a wider gut healing routine. It’s a way to give the body a pause and listen in.

When fasting is not a good idea

There are times when fasting is not recommended. Avoid it if:

• You are currently in a flare-up or in the recovery phase
• You are underweight or struggling to maintain your weight
• You take medications that require food (always check with your healthcare provider)
• You have ever had an eating disorder or find fasting emotionally triggering

In these cases, the risks outweigh the possible benefits and there are many other ways to support gut healing that are more appropriate.

For some, using supplements like resveratrol may offer a partial alternative, as it mimics certain beneficial pathways triggered by fasting without requiring a food break. (Read my resveratrol and IBD blog here LINK)

How to try a one-day fast or digestive rest

If your body is in a good place and you’re curious to try it, here’s a safe way to do it.

The night before: 

Have an early evening meal that is light and gentle, such as steamed vegetables and white fish or a simple soup with some soft grains like rice.

During the fasting day:

Drink fluids such as water, clear vegetable broth or mild herbal teas

Avoid caffeine as it stimulates the gut and can increase stress hormones

Rest or do light movement like stretching or walking

Notice how your body feels throughout the day

If at any point you feel dizzy, unwell or overwhelmed, eat something. This is not about testing willpower or pushing through discomfort. The purpose is to support your system, not deplete it.

Breaking the fast: 

Choose a soft, easily digested meal in the evening such as cooked sweet potato, soft greens and a small amount of protein. Avoid anything too spicy, fatty or that you know upsets your body.

Alternatives to full fasting

If a full day feels too much, you could try:

• A shorter fast, such as overnight for 12 to 16 hours
• A “broth day” where you consume light, mineral-rich vegetable broths and clear soups instead of solid food
• Simply taking a break from rich, processed or difficult-to-digest foods for a day or two

These options can still offer digestive rest without the need to fully fast.

Final thoughts

Fasting is not a cure for Crohn’s or colitis, but it may be a useful tool for some people during quiet phases of the condition. Used wisely and occasionally, it might help calm the gut, reduce reactivity and offer a reset when needed. As always, listen to your body, go gently and adapt based on what feels right for your system.

References

Longo, V. D. & Panda, S. (2016). Fasting, circadian rhythms and time-restricted feeding in healthy lifespan. Cell Metabolism, 23(6), 1048–1059

Rangan, P. et al. (2019). Fasting-mimicking diet modulates microbiota and promotes intestinal regeneration to reduce inflammatory bowel disease pathology. Cell Reports, 26(10), 2704–2719.e6

Youm, Y. H. et al. (2015). The ketone metabolite β-hydroxybutyrate blocks NLRP3 inflammasome-mediated inflammatory disease. Nature Medicine, 21(3), 263–269

Cignarella, F. et al. (2018). Intermittent fasting confers protection in CNS autoimmunity by altering the gut microbiota. Cell Metabolism, 27(6), 1222–1235.e6

Levine, A. & Wine, E. (2013). Effects of enteral nutrition on Crohn’s disease: clues to the impact of diet on disease pathogenesis. Inflammatory Bowel Diseases, 19(6), 1322–1329