What is the keto flu?

By now, you've likely heard of the ketogenic diet — or keto, for short. Originally designed to treat epilepsy in children, the high fat, low-carb diet has become a popular weight loss method in recent years (via Cleveland Clinic). While data on the diet's effectiveness for weight loss is limited, some evidence suggests it may help people lose a few pounds, at least at first, according to Harvard Health Publishing. But the eating plan can come with side effects, including the dreaded "keto flu." The illness is not an actual medical diagnosis but has become a popular term for a group of symptoms, including nausea and fatigue, many people experience within the first week of starting the keto diet.

Typically consisting of 70 to 80 percent fats, 20 percent protein, and 5 to 10 percent carbohydrates, the diet forces the body to switch from burning glucose to burning ketones for energy, a process called ketosis. This results in a sped-up metabolism, decreased hunger, and increased muscle mass (via Cleveland Clinic).

What are the symptoms of keto flu and how do you feel better?

Keto flu may appear two to seven days after beginning the new eating plan. Symptoms include headache, brain fog, nausea, vomiting, diarrhea, constipation, muscle aches, weakness, fatigue, dizziness, trouble sleeping, irritability, and sugar cravings (via Healthline). Despite its name, it is not related to the flu, the illness caused by the influenza virus. You will not experience a fever and the symptoms should not be very severe.

It is unclear what exactly causes the keto flu, but experts believe the dietary change may come as a shock to the body and lead to withdrawal-like symptoms in some people. It's important to note that not everyone who tries the keto diet will develop the keto flu. If you experience symptoms, make sure to stay well-hydrated, as the keto diet can cause the body to rapidly shed water, which increases the risk of dehydration. Avoid strenuous exercise and get plenty of rest. If you're having a really hard time adjusting to the diet, you may need to take a more gradual approach, slowly reducing carb intake rather than a quick cut all at once.