Why does your stomach growl?

Your digestive system is lined with muscles that contract in waves, a process called peristalsis, to push food, liquid and gas along. When the stomach and intestines contain mostly air and fluid, these contractions produce rumbling noises that echo like sound in an empty room. About two hours after the stomach empties, a pattern called the migrating motor complex begins, sweeping leftover material through the gut and often producing loud growls. Hunger hormones such as ghrelin also help trigger these contractions, which is why growling often coincides with feeling hungry. The noises happen after meals too, but food muffles them so they are harder to hear.