Hunger alone cannot exactly burn fat. Just being hungry does not mean your body is burning fat. The body uses sugar for energy in case of hunger and not the fat reserve. It might play a small role, though. However, keep in mind that this process is relatively slow and requires regular exercise, healthy eating habits, and calorie restriction for maximal results. The hormone ghrelin is released in response to a caloric deficit. Ghrelin signals your brain to release stored energy and create new muscle cells. Additionally, increased serotonin levels and norepinephrine may increase thermogenesis (the body's natural ability to burn calories).