A keto diet is actually a very restrictive diet. In the classic keto diet for example, one gets about 80 percent of caloric requirements from fat and 20 percent from proteins and carbohydrates. This is a marked departure from the norm where ketozin the body runs on energy from sugar derived from carbohydrate digestion but by severely limiting carbohydrates, the body is forced to use fat instead.Some people may find after a week or two of using the diet they start to feel better as their brain can switch over to using ketone bodies as a fuel source, but others may never find they begin to feel better.
https://goldencondor.org/ketozin/