Why does your
stomach growl?
For anyone whose stomach has betrayed them in a quiet room
Can't play sound? The illustrated version is right below.
Read the transcript
The full narration of the video.
The quietest second of the meeting, and your stomach growls. Everyone says that's your stomach crying for food. Yet sometimes, right after lunch, it rumbles anyway. So where does the sound come from? Follow one little bubble through your belly and you'll see.
Your stomach and intestines are one soft tube, several meters long, lined with rings of muscle. One ring squeezes, the next follows, wave after wave, pushing everything forward. Besides food, the tube holds water, plus air you swallowed and gas made while digesting.
A wave comes through, the bubble gets squeezed through a narrow spot, and: rumble. So it's not just the stomach; the small intestine growls too. What you hear is gas and water being squeezed along. Then why is it so loud when you're hungry?
Picture the tube as a street, and food as the cars. Right after a meal, they crawl along bumper to bumper. The squeezing goes on, but the bubbles are wrapped in food, so the sound is muffled. Once the food has moved on and the street is empty, out comes the street sweeper.
It's an extra-strong squeeze. It starts at the stomach and sweeps all the way down the small intestine, pushing out leftover crumbs, mucus and bacteria. It comes around every one to two hours, and each pass lasts ten to twenty minutes. On an empty street there's nothing to muffle it, just gas and water. When the sweeper rolls by, the rumble is loud.
Doctors call this sweeper the migrating motor complex. The rumble itself is called borborygmi. Put a stethoscope on a belly, and that's what you hear. When the sweeper sets out, it also sends the brain a note. In one experiment, people felt hungriest during the strongest minutes of the sweep. That's why hunger and growling often arrive together. But hunger doesn't cause the growl. The sweeper just happens to be passing.
Eat something, the cars return, and the sweeper clocks off. One breakfast can park it for over three hours. So why does it growl when you're not hungry? Right after eating, digestion keeps pushing in waves. With enough gas inside, it still rumbles, just more softly.
Soda and beans mean more gas, and a louder rumble. Eating fast or talking while you eat means swallowing plenty of air too. And sometimes the food is long gone, you don't feel hungry yet, but the sweeper shows up on schedule anyway. A growl now and then just means your gut is doing its job. But if it comes with pain, frequent diarrhea or weight loss, see a doctor.
Next time you're worried before a meeting, eat a couple of crackers. The sweeper will most likely clock off. Where was your most embarrassing stomach growl?
The rumble is a squeeze
Your stomach and intestines are one soft tube, several meters long, lined with rings of muscle. One ring squeezes, the next follows, and wave after wave pushes everything forward.
Besides food, the tube holds water, plus air you swallowed and gas made while digesting. When a wave comes through, a bubble gets squeezed through a narrow spot, and you hear a rumble.
It's not just the stomach.
The small intestine growls too.
This ring-after-ring pushing is called peristalsis. Doctors call the rumbling borborygmi. Put a stethoscope on a belly, and that's what you hear.
The street sweeper in an empty belly
Picture your stomach and intestines as a street, and food as the cars. Right after a meal, they crawl along bumper to bumper. The squeezing goes on, but the bubbles are wrapped in food, so the sound is muffled.
Once the food has moved on and the street is empty, out comes the street sweeper: an extra-strong squeeze that starts at the stomach and sweeps all the way down the small intestine, pushing out leftover crumbs, mucus and bacteria. It comes around every one to two hours, and each pass lasts ten to twenty minutes.
On an empty street,
nothing muffles it.
When the sweeper rolls by,
the rumble is loud.
The sweeper's real name is the migrating motor complex: the gut's big clean-up between meals. The street is your stomach and intestines, the cars are food, and the sweeper is that strong squeeze on an empty stomach. One difference: a real sweeper drives in from outside, but nothing drives into your gut. The tube wall squeezes itself, ring by ring.
Hunger and growling often arrive together
Eat something, the cars return, and the sweeper clocks off. One breakfast can park it for over three hours.
Hunger has other sources too: see why we crave food when we're not hungry, and whether you can skip a meal when you're not hungry.
When it growls even though you're not hungry
Where does all that gas end up? See the one about farts.
When to ignore it,
when to get it checked
isn't hunger.
It's the sweeper passing by.
Quick check
Your stomach rumbles right after a meal. Where does the sound come from?
What you hear is gas and water being squeezed along. On an empty stomach the sweeper's squeeze has nothing to muffle it, so it's louder.
