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Does fasting cause diarrhea is a question you might have asked yourself a couple of times before. The answer is yes, fasting may cause diarrhea, even if it’s not common. 2

Millions of people around the world fast for reasons that vary between religious or health beliefs. Although Fasting has many health benefits for different body parts1, it is a double-edged sword in which it might cause dehydration, headache, heartburn, Dehydration, and other side effects.9

Why do people fast?

Fasting is simply described as a period of time when you fully or partially quit eating.3 People fast for a variety of reasons which include:

Religious or Spiritual Obligation

Almost all major religions, including Christianity, Hinduism, and Islam practice fasting.3 For example, Muslims fast for 30 days from dawn to dusk during the holy month of Ramadan. They must not consume any food or drinks, including water, during this time.. 4 On the other hand, Catholic Christians fast 40 days before Easter and consumption of dairy, wine, meat, fish, and oil is off limits. 6

Health Reasons

People often fast due to health aims such as losing weight or preventing or even reversing some forms of disease. 3 Intermittent fasting is an eating plan that switches between fasting and eating on a regular schedule. Research shows that intermittent fasting has many health benefits, including managing your weight, boosting memory, improving blood pressure and heart rates, and reducing blood glucose levels and preventing obesity.7

On the other hand, and from a health point of view, Ramadan fasting significantly lowers the risk of diabetes, heart disease, and total and LDL cholesterol. But this information needs more investigation to be more applied. 5

What happens to our body during fasting?

Energy is something that the body will always need, and in most cases, people acquire most of their glucose from meals. But once we stop eating, the glucose that has been stored in the muscles and liver is released into the bloodstream as needed. Fasting, however, alters this mechanism.8

After a fast of approximately 8 hours, the liver will use the last of its glucose reserves. The body now starts a process known as gluconeogenesis where it starts making its own glucose from fat. Then it starts to break down muscle when glucose is low.8

As long as the person is healthy, skipping meals for a day is normally safe. 8 But, In some cases, fasting might be associated with many side effects that people can experience. 9 What are the side effects of fasting?

5 Fasting Side Effects to Watch out for


Occurs when you use or lose more fluid than you take in, and your body doesn’t have enough water and other fluids to carry out its normal functions.


Results from dehydration, hunger, or a lack of sleep during a fasting period.


occurs due to an empty stomach continuing to produce the acids it typically uses for digestion.


results from engaging in very long fasting periods and not replenishing the body with enough nutrients. 11


occurs because of an oversecretion of water and salts in the GI tract.10 Fasting doesn’t cause diarrhea on its own. It can happen, but it’s uncommon. 3

Does fasting cause diarrhea?

As mentioned above, diarrhea is not a common side effect of fasting but it happens. Some people suffer from diarrhea while fasting, others suffer from diarrhea after breaking fast. So, why does this happen?

Diarrhea while fasting

Drinking caffeinated beverages like tea or coffee is one of many causes that can cause diarrhea while fasting. Other causes include: 10

  • Lactose intolerance
  • Poor diet
  • Infection
  • Food allergy

Diarrhea after breaking fasting

Diarrhea after breaking fast is more common.10 Most of the time, breaking your fast increases your risk of developing diarrhea compared to keeping it. This is since when your bowel isn’t used, its capacity to work effectively declines. And When food and liquid move too quickly through your digestive tract, this might result in diarrhea. 2

Intermittent Fasting Diarrhea

People can experience diarrhea while practicing intermittent fasting because they are drinking water to stay hydrated when they are not eating solid food. So, the relationship between intermittent fasting and diarrhea is that your kidneys can suffer damage from having too much water in your body because they are unable to excrete the extra water. This may result in nausea and diarrhea. 11

Treatment of diarrhea

You can treat diarrhea that is caused by fasting using these tips: 12

  • Stay Hydrated: Drink a lot of liquids, such as juices, broths, and water and make sure to avoid alcohol and caffeine.
  • Choose your food carefully: gradually introduce semi solid and low-fiber foods to your diet such as: toast, eggs, rice,or chicken until your bowel motions become regular. Also, try to avoid dairy products and fatty or heavy food.
  • Think about probiotics: Although it is unclear if they can shorten an episode of diarrhea, these microorganisms may help restore a healthy balance to the intestinal system by increasing the quantity of good bacteria. For example, ENTEROGERMINA® is one of the products that can be used in the prevention and management of diarrhea in order to improve and restore the gut’s health. 13
  • Try over-the-counter anti-diarrheal medications: For example loperamide Which may help decrease the frequency of watery bowel movements and manage severe symptoms.

To conclude ..

During a fasting state, diarrhea and its side effects, such as lightheadedness, can be distressing and dangerous. Your body is already more likely to feel lightheaded, exhausted, and queasy while fasting. If fasting causes diarrhea, it only makes these conditions worse.10

Therefore, it is advised to break your fast until your symptoms get better, and then to continue it after you feel better. 10


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