The ketogenic diet has become explosively popular and with it, the keto flu has become a widespread problem. This is not a type of communicable disease that you can pass to your family, friends and co-workers, but it is still very real.

The keto flu is a phase that occurs very early in this eating strategy. The majority of people who follow this eating strategy find that they feel absolutely miserable for a stretch of time right at the beginning.

What is the Keto Flu?

The keto flu is a sensation that is extremely influenza-like in terms of the symptoms it produces. It often occurs right at the beginning of the ketogenic diet when you’re first changing everything you eat. This can make it very difficult for many people to push through and continue on with this type of dieting.

Suddenly eating a large amount of fat at the start of the diet can come with a range of side effects that most people would really rather avoid. That said, for those who do keep up with the diet, the symptoms will usually subside in favor of feeling quite energized.

Why Does Keto Flu Happen?

To start, it’s important to note that this is not an actual disease. It may have similar symptoms, but it’s not contagious. It isn’t caused by a virus, bacteria, yeast or even an allergy. Instead, the symptoms appear as the body acclimates to an entirely different type of diet. When you’re not used to eating that much fat, your body isn’t used to having to process it. It needs time to adjust.

The symptoms are quite similar to a regular flu, including fatigue, nausea, body aches, dizziness and headache, among others. It doesn’t, however, include the dry cough, chills and certain other flu symptoms.

The Goal: Ketosis

Once the body adjusts to the new diet, it enters into a process called ketosis. This is the goal of the keto diet. It occurs when the body starts using fat as an energy source instead of relying on carbohydrates. During the transition, the body actually goes into carb withdrawal. It is that withdrawal that comes with the symptoms that are synonymous with starting this diet.

For some people, the symptoms come and go within a day or two. However, others suffer for notably longer, having to try to push through the flu-like symptoms for up to two weeks.