Intermittent fasting is a pattern that involves eating for certain periods throughout the day and fasting for others. Some people experience constipation while intermittent fasting.

It is possible that dietary changes related to intermittent fasting — for example, eating fewer carbohydrates and fiber or consuming less water— might explain why some people have constipation. However, more research is necessary to fully explain the link between them.

People who experience constipation can try home remedies and simple measures to alleviate symptoms, but prolonged or severe constipation warrants a conversation with a healthcare professional.

Read on to learn more about the relationship between intermittent fasting and constipation.

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Researchers have not systematically studied the link between intermittent fasting and constipation. However, research on intermittent fasting has found that some people experience constipation.

Constipation can occur when a person changes their diet or fluid intake or when the health of their gut changes. Fasting may, therefore, indirectly cause constipation in one of several ways:

  • Consuming fewer carbohydrates might cause constipation. This is especially true if a person reduces their intake of complex carbohydrates that are rich in fiber.
  • Eating fewer fruits and vegetables. Both are sources of fiber that can reduce constipation.
  • Not drinking enough water and fluids. Often, people may forget to drink it when fasting.

Dietary fiber is important in preventing constipation and helping regulate intestinal motility. Motility refers to how muscles contract in the gastrointestinal tract to help the digestion process. Both soluble and insoluble fiber are beneficial to health.

Additionally, people get much of their daily fluids from food. So people who are fasting may consume fewer fluids, especially during periods when they are not eating.

People with other risk factors for constipation may find that their constipation worsens when fasting. Some risk factors include:

  • taking certain medications
  • drinking too much alcohol
  • overusing laxatives

Anecdotally, some people who intermittently fast report that their constipation goes away after an initial introduction period of a few days to a few weeks.

Some people may continue getting enough fluid and fiber when fasting and may not experience constipation.

Learn more about intermittent fasting.

Doctors usually define constipation as fewer than three bowel movements per week. However, a person may feel constipated whenever they experience a decrease in the number of bowel movements they have.

Some symptoms a person might notice include:

A person who eats less while intermittent fasting might also have fewer bowel movements, but this alone does not necessarily mean they are constipated.

Learn about having constipation and still passing stool.

A person should use the same strategies for intermittent fasting-related constipation that they would use for any other type of constipation. Strategies include:

  • drinking plenty of water
  • avoiding low fiber foods, such as fast food, chips, and processed foods
  • eating many high fiber foods, including fruits, vegetables, and whole grains
  • exercising more often, as this can help to promote greater movement in the digestive tract
  • using the bathroom on a regular schedule

If constipation persists, ask a doctor about the next steps. Sometimes laxatives can help relieve short-term constipation.

Chronic laxative use, however, may make a person dependent on laxatives for bowel movement.

Learn how to treat constipation naturally.

Some tips for people to reduce the risk of constipation while intermittent fasting include:

  • trying never to delay a bowel movement
  • filling a large bottle with water and carrying it throughout the day
  • avoiding fasting for prolonged periods
  • pre-preparing high fiber snacks in advance and keep them in the fridge for daily use
  • remaining or becoming physically active while fasting – people who feel too tired to exercise when fasting may need to try a different strategy

Learn more about staying on track when trying intermittent fasting.

Constipation can be painful and unpleasant, but it is not usually dangerous. Some strategies to prevent constipation are very effective, and people considering intermittent fasting should also consider approaches for lowering their risk of constipation.

If constipation persists for several weeks or continues after a person stops fasting, they should see a healthcare professional. Sometimes health problems, such as anatomical issues, muscle weakness, nerve damage, or digestive health problems cause constipation, but these are typically treatable.