Low Carb diets also control hunger. A diet rich in carbohydrates releases an abundance of insulin which stimulates the appetite center in the brain. Low carb diets produce ketones, as a natural by product of fat metabolism. They are beneficial, as they can be used as a source of energy, thereby sparing lean muscle tissue. As carb levels decrease, protein intake must increase.
Extra protein is needed to supply energy without adding any more insulin to the body.
The types of calories consumed is the key to this whole thing. The body is capable of rendering energy from either any combination of protein, fat and carbs. By restricting carbs to less than 100 grams per day, closer to 60 grams if possible, the body gradually uses up most of it's glycogen, and the body begins to liberate stored fat and use it as it's primary fuel source. Insulin release is directly related to carbohydrate intake, elevated insulin levels are antilipolytic and slow down the mobilization of fat from adipose tissue. Keeping carb levels low limits insulin release and speeds the fat burning process.