How does the keto diet work?

As Ewoldt explains, a typical American diet consists of 50% or more carbohydrates, which convert to glucose in the body. Your cells burn that glucose as fuel. But when you switch to a very high-fat, low-carb diet, your body, by necessity, shifts away from glucose and instead uses fatty acids and ketone bodies for energy. This process is called ketosis — hence the diet's name.