Can a keto diet cause constipation?

People who follow a keto diet may experience mild constipation that lasts a few days to a few weeks.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, people who have constipation often experience one or more of the following symptoms:

• fewer than three bowel movements per week
• hard, dry, or lumpy stools
• pain or difficulty passing stools
• partially passing stool, which is called incomplete evacuation

Reasons why someone might experience constipation while on a keto diet include:

Transitioning too quickly

Drastic changes to a person’s diet can negatively affect their digestive system and even cause symptoms, such as nausea or constipation.

The body needs time to adjust to a diet. Gradually transitioning to a low carbohydrate diet over a few weeks may help prevent undesirable digestive side effects.

Not eating enough fiber

People who follow a keto diet usually consume 20–50 g of carbohydrates per day. This amount is much lower than the recommended daily value of 300 g of carbohydrates per day.

Although people can benefit from limiting their intake of simple carbohydrates and processed foods, keto diets restrict all types of carbohydrate, including those present in high fiber fruits, vegetables, and grains.

The digestive system cannot break down fiber, so it stays in the GI tract and adds bulk to stools by drawing water into the intestines. This added bulk and water helps keep stools soft and bowel movements regular. Without fiber, constipation may be more likely.

Treatment

The side effects that occur when people transition to a keto diet should clear up once the body adjusts. However, these side effects may discourage people from continuing the diet.

People who experience persistent constipation or have just started a keto diet may wish to consider the following treatments to manage their symptoms:

• staying hydrated
• exercising regularly
• walking after meals
• eating high fiber, low carbohydrate foods, such as cauliflower, cabbage, and berries

If a person’s constipation does not improve after implementing these lifestyle and dietary changes, they can try using a low carbohydrate laxative, such as polyethylene glycol (MiraLAX).

Fiber supplements can also help relieve constipation. However, these products may contain carbohydrates, which could impair the body’s ability to maintain ketosis.

People should speak with a healthcare professional before starting a new medication or supplement.

The transition to a keto diet can result in symptoms that resemble those of withdrawal, such as confusion, irritability, and increased sugar cravings.

The normal balance of electrolytes and other minerals changes when the body stops using glucose as its primary source of energy and starts converting fat into ketone bodies.

This imbalance can lead to flu-like symptoms, which people often refer to as keto flu. Some of these symptoms include:

• increased urination
• dehydration
• fatigue
• lightheadedness
• sweating
• chills
• nausea
• muscle soreness

The following tips may make the transition to a keto diet easier by lowering the risk of side effects, such as constipation and keto flu.

When switching to a keto diet, people may find the following steps helpful:

• reducing daily carbohydrate intake gradually over a few weeks
• drinking plenty of water
• exercising regularly
• avoiding simple carbohydrates
• eating high fiber and low carbohydrate foods, such as vegetables, berries, and chia seeds
• avoiding foods that may upset the digestive system, such as processed foods or fast food

Summary

A keto diet has several potential health benefits, but it does come with risks, including constipation.

With a careful transition to a keto diet — for example, gradually reducing carbohydrate intake, staying hydrated, and including high fiber foods in the diet — people can avoid this.

If constipation or other adverse effects of the keto diet persist, a person should see a doctor.