Why does the keto diet cause flu-like symptoms?

People following the ketogenic diet may experience minor, short term symptoms, such as nausea, fatigue, and headaches. Some call this the keto flu.

Another name for the keto flu is keto induction, as these symptoms tend to occur when people start the diet. The symptoms develop when the body enters a state of ketosis, during which it burns fat for energy.

People can manage or prevent the keto flu by:

> altering the types of fats that they eat

> taking certain medications

> consuming more fiber, vitamins and minerals, and water

In this article, we describe the keto flu and offer tips for preventing and managing these symptoms.

What is keto flu?

Keto flu refers to a set of symptoms that people may experience when they start the keto diet. These are usually minor and short term, lasting between a few days and weeks.

Symptoms of the keto flu include nausea, vomiting, headaches, and fatigue.

These symptoms arise as the body gets used to operating with fewer carbohydrates and as it enters a state of ketosis. The symptoms result from temporary imbalances in energy sources, insulin, and minerals in the body.

Why does keto flu happen?

Carbohydrates are the body's main energy source. On the keto diet, a person reduces their carb intake to fewer than 50 grams (g) per day, compared with the recommended 200–300 g per day.

When the body does not take in enough carbs to use for energy, the liver begins to produce glucose for energy, using its stores. This process is called glucogenesis.

Eventually, the liver will not be able to produce enough glucose to keep up with the energy demands of the body.

The body will then start to break down fatty acids, which will produce ketone bodies, in a process called ketogenesis. Body tissues then use ketone bodies as fuel, and the body enters a state of ketosis.

The medical community considers nutritional ketosis to be safe for most people. However, people may experience symptoms.

The lack of carbohydrates decreases the amount of insulin in the bloodstream. As a result, people may experience an increase in the amount of sodium, potassium, and water that is released in the urine, which will cause dehydration.

Insulin is also involved in transporting glucose to the brain. Before the brain starts to use ketones for energy, it will have less fuel. This will occur for about the first 3 days of the diet before blood glucose returns to regular levels.

Symptoms may reduce as the body reaches a state of nutritional ketosis. This involves the blood concentration of a particular ketone body, called beta-hydroxybutyrate, being 0.5 millimoles per liter or more.

According to one scientific profile of the diet, keto flu can involve the following symptoms:

> nausea

> vomiting

> headache

> fatigue

> dizziness

> sleeplessness

> difficulty with tolerating exercise

> constipation