Your stomach can growl at any time — not just after you've eaten — but when there's food in your stomach or small intestine, the growling is less obvious. It's like when you put a pair of sneakers in the dryer by themselves versus with a load of towels. The towels muffle the noise of the shoes as they bounce around.
But if you're hungry and your stomach is empty, that's when you notice your stomach growling the most. Are those same muscle contractions that digest food to blame here as well? Sort of.
When your stomach is empty, your brain releases an appetite-stimulating hormone called ghrelin. It signals the digestive muscles to restart the process of peristalsis, or to contract. This is again the rumbling you hear.
But why? Two reasons: First, those contractions are "sweeping up" any food bits they might have missed the first time around. Second, those vibrations and rumblings of your empty stomach are designed to make you hungry. The muscle contractions will come and go about every hour until you eat again.
In some cases, of course, excessive grumbling could be a sign of an upset stomach, but you shouldn't be too concerned unless the sounds include cramping, nausea, vomiting or constipation.
So now that we know what causes stomach growling, is there any way to control it? One tip to mute a noisy belly is to eat many small meals instead of a few large ones. Your digestive system will have less opportunity to create those peristalsis rumbles if your body has something tasty in it. Also, eating fewer foods that cause gas may help decrease the growling.