No human population has ever lived in a permanent state of ketosis. Ketogenic diets are dangerous for pregnant women and developing fetuses, and the only human population that has ever subsisted on this dietary pattern advocated by keto diet proponents could only do so because of a genetic mutation that prevents them from going into ketosis. Unfortunately, it has the unintended but unavoidable consequence of reducing the survival prospects of their infants.
On a ketogenic diet, your entire body switches its fuel supply to run mostly on fat, burning fat 24-7. When insulin levels become very low, fat burning can increase dramatically. It becomes easier to access your fat stores to burn them off. This is great if you’re trying to lose weight, but there are also other less obvious benefits, such as less hunger and a steady supply of energy. This may help keep you alert and focused.