Keto diet: here’s why some people experience fatigue, nausea, headaches after starting it

After we eat, the body converts carbohydrates into blood sugar (known as glucose), which it uses for energy. But the ketogenic diet is based on research from the 1920s that found lowering the availability of carbohydrates made the body rely more on using other substances (such as fat) for energy. By metabolising fat to produce glucose or energy, the body generates ketones in the process – hence the term “ketogenic”. Any diet containing less than 20g per day of carbohydrate is deemed to be ketogenic.