- “Michael Jenson, MD, a professor of medicine in the division of endocrinology, diabetes, and metabolism at the Mayo Clinic, calculated this breakdown of how your body processes food. 10 percent to the kidneys. Kidneys work to make sure the blood is balanced with the right amounts of water and nutrients. 5-10 percent to the heart. The heart gets most of its energy from fat, which provides more long-term energy for the hardworking heart than glucose can. 23 percent to the liver, pancreas, spleen, and adrenal glands. After the liver pulls out nutrients, it stores excess calories as glycogen. 25 percent to muscles. Muscles require a constant source of energy just to maintain their mass, so the more muscle you have, the more calories you burn. 10 percent to the brain. Glucose is brain fuel. It can’t be stored long term, which is why people often feel faint if they skip a meal. 10 percent to thermogenesis. The simple act of breaking down the food you just ate takes up one-tenth of your calories. 2-3 percent to fat cells. Your fat cells grow and eventually divide as more and more calories are deposited. 10 percent to no one knows where. Your body’s a big place, and some calories go unaccounted for.” The New Abs Diet: The 6-Week Plan to Flatten Your Stomach and Keep You Lean for Life (The Abs Diet) (David Zinczenko and Ted Spiker).