Fasting to Reset and Heal the Digestive System

Written and medically reviewed by Nicole Grant, RD

Fasting has long been recognized as a powerful practice for improving overall health and well-being. Beyond its effects on weight management and metabolism, fasting offers specific benefits for resetting and rejuvenating the digestive system. In this article, we’ll explore the reasons why fasting is considered an effective method to restore digestive health and promote optimal functioning.

Why Fast to Reset the Digestive System?

Adults of all ages and backgrounds are likely to encounter digestive troubles — in chronic or episodic bouts — and often seek ways to reset their digestive system. Factors such as poor diet, stress, sedentary lifestyles, and the use of certain medications can contribute to digestive discomfort, bloating, constipation, or diarrhea. Fasting can help by allowing the digestive system to take a break from the work of processing food.

By abstaining from eating for a specific period, you can provide your digestive system an opportunity to heal and regain balance. This can help address issues such as irregular bowel movements, inflammation, or imbalances in gut microbiota. Resetting the digestive system through fasting allows individuals to regain control over their gut health and establish a fresh start, promoting improved digestion and overall better gastrointestinal well-being.

How Long to Fast to Reset Your Digestive System

The time it takes for the gut lining to repair itself varies based on factors like age, the extent of damage, overall health, and dietary habits. Typically, the gut lining can begin repairing itself within a few days due to the high turnover rate of intestinal cells, facilitating minor damage repair and maintenance of the intestinal barrier function.

While a prolonged fast of 3–5 days aligns with the gut lining’s turnover rate and facilitates cell regeneration, studies have shown that shorter fasts of around 16–24 hours can still yield positive changes in the gut microbiome, offering digestive benefits without the need for an extended fast.

It is important to note that more severe damage or conditions like intestinal permeability may require a longer healing period, ranging from a few weeks to several months. If you feel you may have serious digestive issues, it’s crucial to address the root cause of the damage and seek a comprehensive healing plan under the supervision of a medical professional. 

In more severe cases, it is best to partner with your health care practitioner in order to decide which fasting protocol might work best in conjunction with other lifestyle changes. Fasting longer than seven days is typically not recommended without close medical supervision; however, a regular practice of time-restricted eating along with occasional extended fasts might be a more sustainable option. For example, a routine TRF habit in which you regularly fast for at least 16 hours can provide a great baseline in which your gut has time for rest and recovery. Extended fasts may be something you engage in less frequently, or on an as-needed basis.

After the holiday season might be a great time to allow for more intensive gut-rest fasting. If you would like to improve your gut health for a specific reason, extended fasts might be something you engage in every 4 to 8 weeks. If you are taking a more preventative approach, you might prefer extended fasts for gut rest quarterly, or biannually. Healthy, whole foods are important for the gut, but intermittent-fasting research in animals and humans demonstrates that the gut is better able to maintain the living cells and the microbiota when it has some time free of digestion demands.  

How Fasting Works to Reset the Digestive System

Intermittent fasting provides periods of rest for the digestive system, reducing the constant workload of digesting and absorbing nutrients. This rest period can reduce inflammation in the gut and improve issues such as bloating and irregular bowel movements. Intermittent fasting can also influence the gut microbiota, promoting the growth of beneficial bacteria and reducing harmful ones.

The migrating motor complex (MMC) is a pattern of electrical activity observed in the gastrointestinal (GI) tract that occurs approximately every 90–120 minutes during a fasting state. It is a housekeeping wave that sweeps undigested material through the digestive tract. When you’re constantly eating, the MMC doesn’t get a chance to complete its cycle, but with intermittent fasting, the MMC can function more effectively, which can help to prevent the buildup of undigested food and unwanted bacteria in the gut and improve overall gut health.

Benefits of Fasting to Heal Digestive Problems

Fasting can support your digestion by contributing to lower inflammation, better gut health and even result in a healthier body weight.

Reduced Inflammation

Although research is still emerging, a few animal studies have demonstrated that the shifts seen in the gut microbiome in relation to fasting can reduce proinflammatory microbes and enhance antioxidant microbial pathways. These findings suggest that fasting might have potential health benefits by promoting a favorable balance of gut bacteria that helps reduce inflammation. 

Improved Gut Health

Fasting can contribute to improved gut health in several ways. Firstly, it provides rest for the digestive system, allowing it to recover and enhance its future function. Digestion requires energy and resources from the body. By fasting, you provide a break for the digestive system, allowing it to rest and recover. Proper rest can also enhance the future function of your gut. Intermittent fasting has been shown to enhance parasympathetic activity (or the “rest and digest” response), resulting in the release of digestive enzymes, increased blood flow to the digestive organs, and promotion of bowel movements.

Secondly, fasting has been shown to improve the gut microbiome. It can positively influence the composition and diversity of the gut microbiome — the trillions of microorganisms residing in the digestive tract. A healthy gut microbiome is essential for proper digestion, nutrient absorption, and overall gut health. Fasting may help promote the growth of beneficial bacteria while reducing the populations of harmful microbes.

Lastly, fasting supports enhanced nutrient absorption. Fasting can help improve digestive processes by allowing the body to clear out any accumulated waste or toxins. This can optimize nutrient absorption and utilization when you resume eating. Additionally, fasting has been suggested to increase digestive enzyme production, potentially aiding in the breakdown and assimilation of nutrients.

Promoting Weight Loss

The gut microbiome plays a critical role in weight management by influencing metabolism, digestion, and nutrient absorption. Certain bacteria in the gut, such as Firmicutes and Bacteroidetes, are found in differing proportions in obese versus lean individuals. When the natural synchronization of our internal body clock is disrupted due to irregular eating patterns, an imbalance in these microbiota, known as dysbiosis, is often linked to weight gain and metabolic disorders. 

Fortunately, fasting has been shown to help better regulate your internal clock and the natural circadian rhythms of your cells and microbes within your body. 

Types of Fasting to Consider for a Digestive Reset

Time-restricted eating, alternate-day fasting, and multi-day fasting are dietary approaches that incorporate periods of fasting to enhance digestion and overall health. Ranging from daily cycles of fasting and eating to extended multi-day fasts, these practices provide varying levels of rest for the digestive system, promoting cellular renewal and a healthier gut environment.

Intermittent Fasting

Time-restricted eating, commonly referred to as intermittent fasting, involves alternating periods of fasting and eating within a daily cycle. The most popular method is the 16:8 fast, where you fast for 16 hours and restrict your eating window to 8 hours. This approach can provide beneficial effects for digestion, microbiome, and overall health when practiced consistently over an extended period of time.

Alternate-Day Fasting

Alternate day fasting is a form of intermittent fasting where individuals alternate between fasting days and non-fasting days. On fasting days, calorie intake is significantly reduced or eliminated, while non-fasting days allow for normal eating. This type of fast can help reset the digestive system by giving it a more extended period of rest and promoting autophagy, a cellular repair process. To obtain the best gut-rest benefits with this protocol, it’s ideal to consume zero calories on fasting days.

Multi-Day Fasting

Multi-day fasting involves fasting for multiple consecutive days. Common durations for multi-day fasts range from 2–7 days. These types of fast can allow for complete cellular turnover of the intestinal wall, since the typical rate is between 3-5 days. This creates an environment free of potential irritants from food, allowing for your gut to rebuild itself in a time of rest.

However, extended fasts should only be attempted under medical supervision, as they require careful monitoring of hydration levels and nutrient intake to avoid potential risks. Always speak with your health care practitioner to help determine if fasting is right for you.

Tips for a Successful Digestive Reset Fast

A digestive reset fast is essentially a way to ‘reset’ your digestive system by giving it a break from processing food. This can help to improve gut health and reduce inflammation. Here are some tips to make your digestive reset fast successful.

#1) Be Mindful of What Breaks Your Fast

Fasting for gut rest is a bit different from fasting for metabolic health or weight loss. In the latter examples, there is a bit more leniency on what breaks your fast, usually allowing for a small amount of calories from food, supplements, and coffee. Gut rest fasting is a bit more strict, typically allowing only for those foods, beverages and supplements that have 0 calories and that do not stimulate the gut — usually water, plain electrolytes, and herbal teas only. 

For example, even though black coffee contains minimal to no calories, it does promote functions of digestion. Coffee stimulates gastrin (a hormone that stimulates secretion of gastric acid), gastric acid secretion, and gallbladder contraction, all of which have an impact on our gastrointestinal tract. 

#2) Stay Hydrated

During a fast, it’s crucial to stay hydrated. Keeping up with your water intake is important. Plus, for extended or multi-day fasts, electrolytes are typically needed. If electrolytes such as sodium, magnesium, and potassium are plain, without other added ingredients, they will not break your fast for digestive rest.

#3) Choose the Right Fasting Period

The length of a fast can vary, and it’s important to choose a period that suits your lifestyle and health. Intermittent fasting, such as the 16:8 method, can be a good goal to start. If you’re new to fasting, you can even consider a few days of 12:12 fasting and work your way up from there.

#4) Exercise Moderately While Fasting

Physical activity can help maintain a healthy digestive system, so it is important to keep up your exercise habits while fasting. However, during a multi-day fast, it’s also good not to overdo it. So, in that case, opt for gentle exercises like yoga, walking, or stretching.

Breaking Your Fast to Maximize Digestive Health Benefits

Breaking your fast in a mindful way is crucial for maximizing digestive-system health benefits. After a fasting period, especially if it’s a prolonged fast, your digestive system has been in a resting state, so reintroducing food should be done carefully to avoid discomfort and make the most of the benefits your fast has provided. Start by consuming small quantities of easily digestible foods. You could consider a light soup or bone broth, or perhaps a smoothie made with fruits and protein powder. It’s beneficial to include easily digested proteins in your first meal, such as eggs or a protein shake, to help replenish your body’s protein stores without overtaxing your digestive system. 

Hydration is also key during this time, so consider water, herbal teas, or bone broths to support both hydration and gut health. It’s advisable to avoid large meals, as well as foods high in sugar after your fast, as these could be challenging for your digestive system and may lead to discomfort. As you continue to eat post fast, slowly incorporate more complex foods, including a gradual increase in fiber. Easing into fiber consumption can help prevent any sudden changes in your gut and support better digestion. 

By gradually reintroducing food to your system in this way, you allow your digestive system to adjust smoothly, ensuring you reap the maximum benefits from your fasting period.

How to Maintain Digestive Health After a Fast

Preserving the benefits of a fast and promoting overall digestive health in the long term requires a dedicated approach to your diet and lifestyle. Minimizing intake of processed foods and added sugars is one of the key steps to maintaining good gut health. These types of food can negatively impact the balance of your gut bacteria and lead to inflammation, so substituting them with whole foods is advisable.

Focus on upping your fiber intake. The USDA recommends 14 grams of fiber per 1,000 kcal. So, focus on nuts, seeds, legumes, whole and unprocessed grains, fruits, and vegetables to help meet your goals. Fruits and vegetables are not only rich in digestion-aiding fiber but also contain antioxidants and phytochemicals that promote gut health. 

Including fermented foods in your diet, such as yogurt, kefir, sauerkraut, or kimchi, can also be beneficial, as these foods are rich in probiotics that contribute to a healthy gut microbiome.

Staying well-hydrated is essential for overall health, but it is particularly important for digestion. Water aids in softening stool and promotes regular bowel movements, helping to prevent constipation. 

In addition to diet, moderate exercise plays an important role in maintaining a healthy digestive system. Regular physical activity can help stimulate the natural contraction of intestinal muscles, aiding in digestion and preventing constipation.


By providing periods of rest to the digestive system, fasting aids in the restoration of gut health, including the repair of the gut lining and the rebalancing of gut microbiota. Depending on individual needs, one can choose from fasting practices such as time restricted feeding, alternate-day fasting, or multi-day fasting. The process must be approached carefully, with a focus on proper hydration, moderate exercise, and breaking a fast with digestible foods. Post fast, maintaining digestive health requires a balanced diet, regular physical activity, and adequate hydration.

Nicole Grant, RD
Posted in Health & Science

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