Tummy growls are really just internal farts, according to Indiana Public Media's "A Moment of Science."

Basically, the involuntary muscle movements that push food through your digestive tract keep working even after most of that food has moved on down the line. Eventually, gas bubbles are all that's left to be squeezed, and you get a rumbling sound as they pop. It's part of how your intestine keeps itself cleansed—no expensive pills or powders required!

The same contractions that cause your stomach to growl also clean out the GI tract. To see how this cleaning movement works, picture a long hose made of a pliable material. If there were an object, say an egg, at one end of the hose, you could push it from that end to the other by squeezing all along the length of the hose. … In order to push out bits of food particles left over from a meal, your gastrointestinal tract creates waves of contractions all along the length of the intestines at a rate of two or three per minute.

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