The ketogenic diet, more commonly called the keto diet, involves a severely restricted carbohydrate intake. People who follow the keto diet compensate for this reduction in carbohydrates by increasing their intake of high fat foods and eating moderate amounts of protein.
These dietary adjustments can sometimes cause mild constipation. Keep reading to learn more about the keto diet, including how it may cause constipation and how to treat it.
When people think of carbohydrates, they often picture grain-based foods, such as bread and pasta. Although it is true that eating too many simple carbohydrates, such as refined sugar, can negatively affect people’s overall health, carbohydrates exist in both healthful and unhealthful foods.
The main types of carbohydrates in food include sugar, starch, and fiber, which are present in fruits, vegetables, and grains.
The term carbohydrate refers to a group of molecules that cells can break down into a simple sugar called glucose.
Glucose acts as the body’s primary source of energy because cells can easily convert it into adenosine triphosphate (ATP) through a process called glycolysis.
People who follow the keto diet consume very small quantities of carbohydrates, usually limiting the intake to less than 50 grams (g) per dayTrusted Source. This restricted intake means that their body will need an alternative source of energy.
In the beginning, the body will tap into its glycogen stores. Glycogen is a larger, more complex form of glucose that the body metabolizes after it burns through all of the readily available glucose.
When the body has exhausted its glycogen stores, the liver starts converting fatty acids into water-soluble molecules called ketone bodies. The cells can use these ketone bodies as an alternative source of energy when glucose is unavailable. When this happens, the body enters a state of ketosis.
According to the authors of a 2018 review articleTrusted Source, keto diets may have health benefits beyond weight loss. These include:
- improving blood sugar control
- reducing triglyceride levels
- lowering total cholesterol levels
The authors of a 2018 literature reviewTrusted Source noted that clinical evidence suggests that keto diets may reduce oxidative stress and inflammation.
They also found evidence to support the use of keto diets for treating various neurodegenerative and neuroinflammatory conditions, such as:
- Alzheimer’s disease
- migraine headaches
Unfortunately, keto diets have their downfalls. People may find it difficult to sustain an extremely low carbohydrate diet for a long time. The transition into ketosis can also cause some undesirable side effects that may discourage people from sticking to the keto diet.
Aside from fatigue and headaches, people may experience uncomfortable gastrointestinal (GI) symptoms. According to one large scale studyTrusted Source on the use of keto diets to treat childhood epilepsy, nearly 50% of children experience the following GI symptoms during the first few weeks of starting a keto diet:
- abdominal pain
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 dayTrusted Source. 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.
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
- 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
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.