Why Does Your Stomach Growl? Hunger Noises and the Gut’s Cleaning Cycle

A long rumble rising from your stomach in a silent meeting room, during an exam or in the middle of an important conversation — that small moment of embarrassment happens to almost everyone. Yet it is actually a sign your digestive system is working properly. So why is the stomach so noisy, and why does it get louder when you are hungry?

The digestive system is a conveyor belt that never stops

The digestive tract, from mouth to bowel, is about 8–9 metres long in an adult. Most of it is a tube with layers of smooth muscle in its walls. These muscles work involuntarily — we do not control them.

They contract and relax in waves to push the contents forward, a movement called peristalsis. It is rather like squeezing a tube of toothpaste from the bottom up.

These waves also move the gas and fluid in the stomach and intestines. As gas bubbles squeeze through narrow sections and fluids slosh about, a range of sounds is produced — the gurgles, rumbles and growls we hear.

These sounds have a name: borborygmi

Doctors call stomach and intestinal sounds borborygmi, from an ancient Greek word that imitates the sound itself. Most of the noise actually comes not from the stomach but from the small intestine — though we call it all “stomach growling”.

Three ingredients make the sound:

• Muscle contractions: the motor that drives the movement.
• Gas: swallowed air, fizzy drinks and gases produced by gut bacteria.
• Fluid: stomach acid, digestive juices and the drinks we consume.

Why does it growl more when you are hungry?

There are two reasons.

1. The soundproofing disappears

When there is food in your stomach and intestines, the sounds come through as if from inside a pillow — food dampens and muffles them. When your stomach is empty, there is little inside but gas and a small amount of fluid. Just as sound echoes in an empty room, rumbling in an empty stomach is far more noticeable.

2. The cleaning cycle starts

Even on an empty stomach, the digestive system does not rest. A few hours after your last meal, a special cycle called the migrating motor complex begins in the gut. It acts like a “housekeeping” routine, sweeping leftover food, bacteria and indigestible particles out of the intestines.

The cycle has three phases and repeats roughly every 90–120 minutes:

1. Quiet phase: contractions almost stop.
2. Irregular contractions: contractions become more frequent and stronger.
3. Strong cleaning wave: a few minutes of very powerful, regular contractions start in the stomach and travel along the small intestine, sweeping everything ahead of them.

The loudest rumbles are often heard during this last phase. The cycle is regulated by a hormone called motilin, and the moment you eat something it stops and the digestive system switches to normal digestion mode.

The hunger hormone plays a part

One of the key hormones that makes us feel hungry is ghrelin. It is released by the stomach wall when the stomach is empty and sends the brain a “time to eat” message. Ghrelin levels usually rise before mealtimes and fall after eating.

Ghrelin affects not just the brain but also the gut, and can increase stomach and intestinal movement. That is why hunger and growling so often arrive together. In people who eat at regular times, the body even “learns” the schedule, and the stomach may start rumbling as mealtime approaches.

Does it growl when you are full?

Yes. The digestive system keeps working after a meal, contracting to mix and move food along — and those contractions make noise too. Because food muffles the sound, though, these rumbles are usually less noticeable.

Some things can make your gut noisier even when you are full:

• Fizzy drinks add extra gas to the stomach.
• Eating quickly, chewing gum and talking while eating make you swallow air.
• High-fibre foods such as beans, lentils, cabbage and broccoli feed bacteria in the large intestine that produce more gas.
• In people with lactose intolerance, undigested dairy leads to extra gas and rumbling.

How to quieten a growling stomach

Stomach growling is completely normal, but you might want to keep it in check before an important meeting. These may help:

When to worry

On its own, stomach growling is almost always harmless. You should see a doctor if it comes with:

• severe or persistent abdominal pain;
• marked bloating and gas;
• prolonged diarrhoea or constipation;
• vomiting, blood in the stool or unexplained weight loss.

Interestingly, doctors listen carefully to abdominal sounds too. A completely silent abdomen can mean the gut has stopped working and sometimes points to a blockage or another serious problem. In other words, regular rumbling is a sign that everything is working as it should.

In short

Stomach growling is the sound of the muscles in the walls of your stomach and intestines moving gas and fluid along — medically known as borborygmi. It gets louder when you are hungry because there is no food to muffle it, and because a strong cleaning wave sweeps through the gut every 90–120 minutes on an empty stomach. The hunger hormone ghrelin boosts these movements too. A growling stomach is simply the natural sound of your digestive system doing its job.