You do not have to eat carbohydrates to have them available for energy. Your body can make carbohydrates as needed, if the protein supply is adequate. Reducing your daily intake of carbs to 72 grams or less . . . will result in more energy at your disposal, as long as you eat plenty of fat and protein. [Further] many organs prefer fat for energy. . .We have all been led to believe that low-fat diets are heart-healthy. But did you know that your heart primarily uses fat for energy? Thatís right. Carbs contributes very little to the energy necessary to keep your heart beating, and the preferred fat is saturated fat.

From Life Without Bread: How a Low Carbohydrate Diet Can Save Your Life by Christian B. Alan, PhD and Wolfgang Lutz, M.D., p 56

Mitochondria are the power plants of the cell. Because they produce most of the energy in the body, the amount of energy available is based on how well the mitochondria are working. . . Mitochondria were specifically designed to use fat for energy. . . Fatty acids [unlike glucose] are transported into the mitochondria completely intact. L-Carnitine is the compound necessary to transport medium- and large-sized fatty acids inside the mitochondria from the cell soup (called cytosol) . . .L-carnitine is chiefly found in animal products [and] is one of many important substances that are only found in appreciable quantities in animal foods . . Ibid, p 64-65