The average human burns glucose (carbs, sugar, etc) as a fuel source. The body uses this fuel easily and tends to defer to this fuel by default. With a very low-carb diet (like keto), there isn’t enough carbs to burn for fuel and your body is forced to use something else instead – fat and/or ketones. Ketones are naturally produced by the body and obviously everyone has a certain amount of fat they can burn (even those that appear thin). With time spent in a carb deficit, the human body will learn how to better utilize fat and ketones as a fuel instead of carbs, hence the term fat-adapted. This is why people following a ketogenic diet typically consume higher amount of fat than your average person, because they need fat for energy since they’re not consuming carbs. This does take time, however, and there is a period of transition that is commonly referred to as “keto flu”, when your body doesn’t have the carbs it is used to but hasn’t quite learned how to burn fat instead. Supplementing with electrolytes can help with this and if you push through it, you can reap the benefits of a higher energy output from fat than carbs and along with it, a clearer mind and sharper focus from your brain using ketones!