It might seem counterintuitive that adding more fat to your diet can lead to weight loss. Normally, your diet is high in carbohydrates, which are broken down into glucose, or blood sugar, for use as energy. As glucose enters your bloodstream, your body releases insulin to store excess glucose as fat. The more carbohydrates, the more glucose. The more glucose, the more insulin, and the more insulin, the more fat.

The keto diet takes advantage of the fact that when your meals are high-fat and low- carbohydrate, there is no insulin spike, and you don't add to your fat reserves. Instead, fat from diet and stored fat are broken down to ketones ("keto" is short for "ketogenic" producing ketones). Like glucose, ketones can be used for energy, keeping your body running without increasing blood sugar or putting on excess fat.