Your body's metabolism is constantly in motion, even as you sleep or sit on a couch zoned out while watching TV. The body will seek resources it needs from the raw materials you feed it. And when those raw materials run low, the body will work its magic to create its own source wherever possible.

Case in point: Most cells can produce glycogen, which is a stored form of glucose. But the liver and muscle cells store the greatest amounts. After you eat, liver cells obtain the glucose from the blood and convert it to glycogen. Between meals, when blood glucose levels fall, the reaction is reversed, and glucose is released into the blood. This ensures that cells will have a continual supply of glucose to support life.

When you take in more carbs than your body can store as glycogen or are needed for normal activities, all that extra glucose becomes fat and is then deposited into your fat cells. The body has an almost unlimited capacity to do this type of conversion, which is why chronic overeating usually leads to obesity.