Diabetes mellitus, often simply called diabetes, is a common disorder in which the body cannot properly use the carbohydrates (starches and simple sugars), fats and proteins in foods. All of these nutrients can be processed by the liver into one type of simple sugar, glucose, which then enters the bloodstream. All body cells require glucose for energy. Glucose enters body cells with the help of a hormone called insulin, which acts somewhat like a gatekeeper. If the body becomes less responsive to insulin, or if the body is not producing insulin, glucose cannot pass through the cell wall and the cell "starves". Because the glucose cannot enter cells, it remains in the blood, which is why people with diabetes have high blood sugar. As a result of cellular starvation and high blood sugar, the body has to work harder to keep functioning, and organs and systems can suffer severe damage.