Fuels and feeds your brain: Ketones provide an immediate hit of energy for your brain, and up to 70% of your brain’s energy needs when you limit carbs. Fat also feeds your brain and keeps it strong. Your brain is at least 60% fat, so it needs loads of good fats to keep it running. Essential fatty acids such as omega-3s help grow and develop the brain, while saturated fat keeps myelin — the layer of insulation around the brain — strong so your neurons can communicate with each other.
Normal dietary fat contains mostly long-chain triglycerides (LCTs). Medium-chain triglycerides (MCTs) are more ketogenic than LCTs because they generate more ketones per unit of energy when metabolised. Their use allows for a diet with a lower proportion of fat and a greater proportion of protein and carbohydrate, leading to more food choices and larger portion sizes. The original MCT diet developed by Peter Huttenlocher in the 1970s derived 60% of its calories from MCT oil. Consuming that quantity of MCT oil caused abdominal cramps, diarrhea, and vomiting in some children. A figure of 45% is regarded as a balance between achieving good ketosis and minimising gastrointestinal complaints. The classical and modified MCT ketogenic diets are equally effective and differences in tolerability are not statistically significant. The MCT diet is less popular in the United States; MCT oil is more expensive than other dietary fats and is not covered by insurance companies.