People adapt to ketogenic diets differently. While some may experience weeks of keto-flu symptoms, others may adjust to the new diet with no adverse side effects.
The symptoms people experience are tied to how their bodies adjust to a new fuel source.
Usually, carbs provide the body with energy in the form of glucose.
When carbs are substantially reduced, the body burns ketones from fat instead of glucose.
Those who typically consume lots of carbs, especially refined carbs like pasta, sugary cereal and soda, may have a more difficult time when beginning the ketogenic diet.
Thus, the transition to a high-fat, very low-carb diet may be a struggle for some, while others are able to switch between fuel sources easily with little to no keto-flu symptoms.
The reason some people adapt to ketogenic diets easier than others is unknown, but genetics, electrolyte loss, dehydration and carbohydrate withdrawal are believed to be the driving forces behind the keto flu.