The benefits of intermittent fasting for gut health are many.
These benefits include:
- Improving the microbiome
- Increasing butyrate
- Aiding in liver health
- Reducing belly fat
- Reduces inflammation
- Helps gut motility
- May help heartburn
- Reduces the risk of several diseases
In this post, learn all about the benefits of intermittent fasting for gut health, the many other benefits of fasting, and how to do a fast without feeling bad.
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Table of Contents
What is Intermittent Fasting?
Intermittent fasting is simply a way of extending the time window between eating.
Fasting actually isn’t a new concept at all, but it deviates from the common dogmatic way of “eating until full” every day or eating whenever hungry. This is the common mode of eating today in Western culture.
Historically, fasting has been done for religious reasons and personal health reasons since the dawn of time. Fasting also has been in place by most humans in history inadvertently due to a lack of food supplies. The exceptions would be kings and royalty who always had food at the ready.
Also known as time-restricted fasting, intermittent fasting methods are the most popular form of fasting because they are the easiest to follow. Technically speaking, all types of fasting are intermittent.
How does one intermittently fast? All you need to do is simply limit the number of hours of feeding during the day. I do most days of the week without difficulty at all.
We all fast, whether we want to see it that way or not. Our body goes through a period of rest, or sleep, where we don’t eat. Often we inadvertently do it for an extended period when we are sick or happen to be low on money to buy food.
Certain fasts, as described below, extend that period of fasting in a variety of ways.
Common Types of Fasting for Gut Health
The 14 10 intermittent fasting method: Simply put, 14 10 intermittent fasting is fasting for 14 hours a day followed by a 10-hour eating window.
While there are many styles of fasting, much research suggests that a 14-hour fast followed by a 10-hour eating window is effective and a good place to start for beginners.
The 16 8 intermittent fasting method: is also a popular fasting method, with 16 hours a day of fasting and 8 hours of eating span allowed. No other requirements.
The 18 6 intermittent fasting method: is a bit more challenging, where eating is restricted to 6 hours during the day. This method may have more weight loss benefits than the other methods, but it can create a bit more stress on the system if done frequently.
Fasting for Gut Health Benefits Overview
Fasting for gut health has long been used as a remedy. Now research is emerging to back its benefits for gut health.
Specifically, fasting helps to improve the gut microbiome of bacteria that dampen inflammation such as Faecalibacterium.
It also enhances the bacteria that increase the production of gut-fueling compounds like butyrate.
Fasting may also help dampen inflammation in people with inflammatory bowel diseases.
During the fasting period, bile acids concentrate in the gallbladder to allow for a bolus of bile to help digest foods when eating a meal. This means you may digest your food better too if you do intermittent fasting.
By improving digestive function, fasting may help with many other aspects of your gut.
Let’s dig in a little deeper.
Fasting for Gut Health: Dampens Inflammation
Without question, fasting has the ability to help dampen inflammation in the body. In a review of 14 clinical studies, intermittent fasting decreased blood markers of inflammation called C-reactive protein according to research published in Nutrition Journal.
Now early research suggests that fasting may help dampen inflammation in people struggling with inflammatory bowel diseases such as ulcerative colitis.
Case reports of people with ulcerative colitis show that 14:10 intermittent fasting reduces inflammatory markers while reducing symptoms of colitis.
This is an important discovery because many inflammatory conditions are driven primarily by lifestyle and not genetics. In fact, only 12 percent of people with ulcerative colitis have a family history of the disease.
Additionally, fasting reduced diarrhea symptoms in women with a type of colitis called collagenous colitis.
In a mouse model, fasting decreased inflammation in the colon and reversed some of the damage of inflammatory bowel disease.
While it is too soon to know for sure if fasting helps everyone with IBD, it is safe for most people to try.
Fasting for Gut Health: Improves the Microbiome
The type and amount of bacteria living in our guts vary a lot depending on our diet patterns and the foods we choose. Not surprisingly, then, fasting has a positive impact on the microbiome.
In fact, multiple studies have shown that intermittent fasting improves the gut microbiome to produce healthier types of bacteria. These bacteria produce compounds that feed the gut lining so it in turn helps to repair the gut.
Fascinatingly, fasting improved the microbiome while also improving immune cell populations compared to the dietary approaches to stopping hypertension (DASH diet) in people with metabolic syndrome. This, in turn, resulted in a reduction in blood pressure and BMI better than the DASH diet.
While this fast was a 5-day fast, shorter fasting windows have shown similar benefits as well. For example, a fast-mimicking type of fast resulted in an increase in Bacteroidetes while decreasing Lachnospiraceae and Ruminococcaceae. This shift in bacteria is related to improvements in butyrate levels.
Ramadan fasting results in similar changes in the microbiome. However, the foods eaten during this timeframe impact the microbiome too. Some, but not all, research shows that Akkermansia mucinophilia is also increased by this type of fasting. This is generally considered a very beneficial type of bacteria for the gut.
Fasting for Gut Health: Helps the Liver
Additionally, fasting helps improve liver health in people with nonalcoholic fatty liver disease according to a review of 14 clinical studies.
Liver health is critical for gut health because the liver makes important digestive compounds including bile. Bile helps carry waste out of the body. The liver also helps break down toxic substances which, in turn, is better for gut health.
May Help You Digest Foods Better
The microbiome promotes a healthy gut. This is partly because probiotic bacteria make digestive enzymes that help break food down into absorbable parts. And because fasting helps to promote a healthy microbiome, it indirectly helps you digest your foods better.
By promoting a concentrated bile amount in your gallbladder, you can digest and absorb your nutrients better too after an intermittent fast.
Fasting for Gut Health: Improves Gut Movements
Another major benefit of fasting for gut health is that it helps promote normal gut motility via the migrating motor complex (MMC). Research shows that the MMC is more active when people are fasting.
In theory, fasting may also reduce symptoms of IBS because it supports a more normal gut motility and may even help with small bacterial overgrowth (SIBO) symptoms. Still, there is no research to prove this theory at this point. But it won’t hurt to try prolonging your fast if you suffer from SIBO or IBS to see if you feel better.
Fasting for Gut Health: Helps with Heartburn
Not surprisingly, fasting may also help reduce heartburn symptoms and gastroesophageal reflux disease (GERD).
After Ramadan fasting, heartburn and GERD symptoms decrease according to a study of 130 GERD patients.
Another study found similar benefits of fasting for heartburn relief.
While more research is needed to determine if other types of fasting may reduce GERD, it’s safe for most people to try.
Fasting for Gut Health Successfully
If you are a person who is used to grazing and snacking all day, it can take some time to get used to fasting.
The first step in breaking the snacking habit is to eat a nutritious and satisfying dinner. This will help prevent snacking later in the evening. As your body gets used to having fewer snacks, it becomes effortless to have a 14-10 fast regularly.
For a 14-hour fast diet, you should stay well hydrated during your fast. Make sure to have plenty of healthy beverages on hand that you enjoy that are calorie-free during your fast.
By the way, if you have less than 50 calories during the fasting window, this is still technically considered fasting.
Fast for Gut Health: More Tips
Having a pinch of Himalayan salt helps replace electrolytes so you can add this to your water or put a pinch of salt under your tongue during the fasting period. This practice can remarkably also help take away hunger pangs or any feelings of nausea or discomfort for many people.
A common window of eating for a 14 10 fast is to eat dinner at 6 pm and then have breakfast the following morning at 8 am. But, there is no right or wrong way to fast as long as you have a 14-hour window of not eating.
The Importance of Being Flexible
The best part about intermittent fasting is that food is not restricted during the eating period. But you should make sure to aim to eat a lot of healthy foods and prioritize protein so that you stay full.
Women may want to avoid fasting while having their menstrual cycles.
PMS hormones may amplify feelings of hunger and cause mood changes when fasting.
I recommend that women, when trying intermittent fasting, stick to fasting in the early part of their menstrual cycle, and try it if and only if their baseline diet is high-quality.
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Fasting for Gut Health: Meal Plan Ideas
As mentioned above, there are no right and wrong ways to meal plan during a fast, but it helps to have balanced meals.
Here are a few examples of an intermittent fasting plan that can help you make the best of a fast. Keep in mind that it can and should be flexible to help meet your lifestyle.
Fasting works more easily for a person who has a well-balanced diet. It is much easier to implement a fast for people who eat pretty well first, so cleaning up your diet first is a good place to start.
Here are some example meal plans for an alternate-day fasting schedule example that follows the 14-10 rule.
Day 1
You ate dinner at 6 pm the night before so your eating window starts at 8 am.
- 6 am: Coffee or tea
- 7 am: Water with a pinch of salt or electrolyte replacement powder
- 8 am: 2 eggs with ½ avocado with herbal tea
- 12 pm: Beef and vegetable stew leftovers and fresh fruit and water
- 6 pm: Salmon with rice and vegetables, herbal tea
- 8 pm: Herbal tea
Day 3
You had a snack at 10 pm the night before so the eating window starts at 12 pm.
- 6 am: Coffee or tea
- 7 am: Water with a pinch of salt or electrolyte replacement powder
- 12 pm: Honey mustard chicken with vegetable and potatoes leftovers
- 2 pm: Herbal tea or water
- 4 pm: Cheese and nuts
- 8 pm: Pork Chile Verde stew with fresh fruit and herbal tea
Day 5
Your last food was at 9 pm so your eating window starts at 11 am.
- 8 am: Coffee or tea
- 10 am: Water with a pinch of salt or electrolyte replacement powder
- 11 am: Plain whole milk yogurt with honey and fruit, fresh green salad with sardines
- 2 pm: Walnuts and cashews
- 7 pm: Mediterranean chicken and olives with quinoa and veggie salad
- 9 pm: Cheese and gluten-free crackers
Other Health Benefits of Intermittent Fasting
Regardless of the type of time-restricted eating, they all affect similar pathways in the body with the end result of less inflammation. By reducing inflammation, fasting potentially reduces the chances of many diseases.
Fasting may help with many conditions, especially the following:
Rheumatoid arthritis-Ramadan fasting reduces inflammatory markers in people with this condition.
High blood pressure-is reduced by fasting, especially with longer fasts. Fasting may help lower blood pressure by promoting better sleep, reducing fasting insulin levels, and an increased ability to relax. The body increases its loss of sodium during a fast as well.
Cancer risk-fasting reduces the risk of cancer and reduces the chance of cancer recurrence and cancer mortality.
Metabolic syndrome-fasting reduces body fat levels, reduces fasting insulin, and increases insulin resistance. Therefore, fasting is an important tool for helping prevent type 2 diabetes.
Improving cardiometabolic health-fasting helps to reduce body fat, body weight, calorie intake, and inflammation. It also may help reduce triglycerides and improve cholesterol ratios.
May help prevent diabetes-fasting may help promote the health of the pancreas and therefore help reduce the risk of type 1 diabetes.
Obesity-a good fasting plan helps increase fat burning especially when combined with exercise. Fasting results in better weight loss than calorie restriction or high-protein diets.
Improves hormones-fasting helps to improve hormone levels, including insulin, adiponectin, and leptin.
May extend lifespan and healthspan-results from fasting trials indicate that by reducing inflammation, and body weight, and improving sleep cycles, fasting may improve lifespan.
Is Intermittent Fasting Effective for Weight Loss?
Yes. Restricted eating windows reduce body weight according to some research. Another study found that 14 10 intermittent fasting results in greater weight loss than 12 12 fasting in combination with a weight loss program for people who are obese.
Of 27 clinical trials in humans, all found that all types of fasting help promote weight loss. The reason that fasting improves weight loss is that restricted feeding improves insulin sensitivity and promotes fat burning during the fasting state.
As logic would have it, the amount of weight that you lose is going to depend on how much exercise you do and what foods you eat when you fast as well.
Does Timing of the Fast Matter?
Fasting later in the day may prove more effective than skipping breakfast.
For example, one research study found that people who ate less than 30% of their calories in the evening had reduced inflammation markers and reduced 24-hour blood glucose markers compared to those who ate more calories in the evening.
Nighttime eating has been linked to an increased risk of cancer as well. Eating late at night also increases the risk of obesity by changing how we store fat. By eating late, you are more likely to suffer from heartburn as well, which can interrupt healthy sleep.
Other Types of Fasting for Gut Health
Many types of fasting exist; in fact, there are infinite ways to “fast.” Here are some of the most common.
Water Fasting
Water fasting is exactly what it sounds like taking in water only for a determined period of time. Some people do it for days in a row. This is a type of fast to ONLY do under complete medical supervision, and as you might imagine, can be very unpleasant.
Side effects are sometimes large, ranging from fatigue to pain and digestive discomfort.
However, water fasting doesn’t seem to have as severe of side effects as some might imagine, at least in research. A large body of data collected only saw 1 hospitalization and no deaths.
Research isn’t without its flaws, however, so I don’t recommend this form of fasting, mostly because it can be quite unpleasant.
Fast-Mimicking
A fast-mimicking diet is a vegan-style fast with 10% of calories as protein. It also has lowish calories for 3-5 days, between 800-1000 calories per day. Following the 3-5 days, people resume their normal eating schedule.
The reduction in protein for a short period of time is done because it can help shut down growth factors that drive inflammation.
In a fascinating study of 100 generally healthy people, simply following a fast-mimicking diet for 5 days out of the month reduced blood pressure, cholesterol, inflammation, body fat, body weight, and fasting glucose compared to “regular” eating.
Fast-mimicking diets also may help repair and replace damaged cells in the setting of autoimmune diseases, according to early data.
In my experience, a fast-mimicking diet is much more difficult to follow than a typical intermittent fast, however.
Religious Fasts
Every religion has fasting in some way, shape, or form.
Food deprivation for short periods of time is thought to bring about closeness to a higher power and enhance the spiritual experience.
It is a form of sacrifice as well as a way of honoring a higher power. Ramadan fasting is a common type of religious fast.
My Personal Fasting for Gut Health Experience
It is important for healthcare providers to be open-minded and as such, open-minded to trying fasting. What better way to learn about it than to do it?
I read a lot of research, and after all these years, I know that research can never describe the human experience.
That is why I am sharing it here with you today. After all, healthcare is both an art and a science.
First, a little bit of information about me. I tend to be lean and thin, regardless of what I eat, so a fast may affect me differently than someone who has a lot of extra pounds.
I have an ectomorph-type build and have a hard time putting on muscle. This is a sign that prolonged fasting should never be in my repertoire. If this describes you, please also avoid extended fasts.
But, as I get older, keeping the weight off my belly has become increasingly harder than when I was young.
By intermittent fasting, I have been able to almost effortlessly lose my belly fat.
When I first started intermittent fasting, I used the 12-12-hour fasting schedule. This allowed me to adapt to less snacking at night and sometimes forgoing breakfast too.
It was a bit challenging at first, but after a couple of days, it was quite easy.
Gradually, I extended my fast to 16 8-hour fasting, and this has become quite easy too. It helps to add in an electrolyte replacement powder drink to get over any feelings of deprivation in the morning or evening.
Fast mimicking, on the other hand, is not my preferred method of fasting. It had some untoward effects on my psychology of eating for me for a while. For example, it made me a little preoccupied with eating when I went back to a normal eating schedule.
This could be a problem for those predisposed to eating disorders. In contrast, I don’t feel any of these problems when I use a 14-10 intermittent fasting schedule when I allow myself to eat the foods I love.
Some people may waste muscle with a fast-mimicking diet. I lose muscle really easily, especially in my upper extremities.
In other words, I much prefer a 14 10 fast or a 16 8 fast to fast-mimicking personally because I keep my muscle mass and energy.
Who Should Fast and Who Should Avoid Fasting?
The potential health benefits of fasting are broad; it can have a “cleansing” effect by dampening down inflammation, reducing the risk of diabetes, reducing body weight, and more.
Some people, such as children and adolescents and those on medications that affect blood sugar, should not try fasting without medical supervision.
Fasting should be done in the context of a usually balanced and healthy diet. If this isn’t you, work on getting your diet balanced first.
Fasting for Gut Health Summary
Fasting for gut health is safe for most people and is effective in helping achieve many health goals.
As always, make sure you inform your healthcare provider BEFORE starting any new health regimen.
Can I get diarrhea from fasting?
Intermittent fasts don’t cause diarrhea as long as they are done properly. However, reintroducing foods might if you don’t eat healthy meals. That said, if you get diarrhea from a fast, you should talk to your healthcare provider.
Can I get constipation from fasting?
Not likely. In fact, fasting is more likely to help alleviate constipation because it may help improve gut movements as described above. However, make sure you don’t allow yourself to become dehydrated during a fast as that can contribute to constipation.
Prolonged fasts, greater than a day, however, may contribute to constipation, although no research has found this.
Is fasting good for your bowels?
Most likely, although no research has been conducted to confirm this.
Does fasting reduce nausea?
Not necessarily. No research has been conducted to determine this.
Should I fast if I’m underweight?
An intermittent fast doesn’t necessarily make people lose weight if they are already lean. Most research shows that fasting can be safely done by anyone. If you want to fast and you are underweight, just make sure to check with your healthcare provider first to determine if it is safe for you. And make sure that you eat enough to support keeping lean muscle during the feeding times.
Heidi Moretti, MS, RD is The Healthy RD. A registered dietitian for 23 years as well as a book author of the new book Gut Fix and The Whole Body Guide to Gut Health, Heidi has a passion for functional nutrition and natural medicine. She has researched supplements and natural medicine throughout her career. One of her biggest loves is helping people gain function and vitality by tackling the root causes of illness.
