Getting into ketosis If you stick to a normal diet, your body gets most of its energy from carbs. What happens, though, is that your body runs out of glucose and starts burning fat for energy when you cut back on carbs a lot, like on the keto diet. If your body is in this state, it's called ketosis. During ketosis, your liver makes ketones, such as BHB, which your brain and muscles use as their main source of fuel.
