The essence of a keto diet is that with a diet low in carbohydrates and high in fat, the body goes into a certain metabolic state - ketosis. It will turn you into a fat burning machine. The subtlety is that you have to drastically reduce your overall carbohydrate intake. This is extremely important - even with a slight excess of the carbohydrate norm, your body will end ketosis, without which a keto diet is impossible. Thus, despite its high effectiveness, the keto diet may seem too strict.