1. Stomach Growls Come from Muscles Moving Food and Gas Through Your Gut
In medicine, stomach noises are called borborygmi. The walls of your stomach and intestines are made of muscle. These muscles squeeze and relax to push the contents forward. This movement is called peristalsis. As the muscles move, the gas and liquid inside your gut move with them. Harvard Health Publishing explains that the sound is created when gas is pushed by the contraction of the intestinal walls [1]. Scientific American also notes that the rumbling occurs when muscles push food, gas, and liquid together while moving them along [2]. However, the exact physical details of how the sound is created are not fully understood yet. It is best to read these explanations as things that are thought to happen, rather than absolute facts.
2. Why an Empty Gut Makes Stomach Noises Louder
It is explained that the growl sounds louder when you are hungry because there is less content in your gut. When there is less in your gut, there is less to dampen the sound [2]. Some explanations also suggest that the empty space inside the stomach can make the sound resonate and grow louder [5]. However, growling is not only about being hungry. Stomach noises happen during and after meals as well. When there is food present, the sound is muffled, so people usually do not notice it [5].
3. The Cleaning Wave: Muscle Contractions in Your Stomach Between Meals
Between meals, when there is little food, your stomach and small intestine are not resting. They perform a regular pattern of contractions called the migrating motor complex (MMC). This happens at intervals of about 90 to 230 minutes. Eating interrupts this movement [4]. The MMC is divided into phases I to IV. In phase III, the contractions are strongest for about 5 to 10 minutes. This wave is said to move hard-to-digest items, like bones or fiber, from the stomach to the small intestine, and then to the large intestine. Because of this, it is sometimes called the "housekeeper wave" [4]. This wave is listed as one cause of the noises heard when you are hungry. The gut hormone motilin is thought to be involved in this wave [7]. It is safe to think of it as just one possible cause. The timing varies from person to person; it is not exactly every 90 minutes. Think of it as happening every 90 minutes to several hours.
4. How Scientists Found the Cleaning Wave in Dogs and Measured It with a Balloon Tube
In 1969, J. H. Szurszewski at the Mayo Clinic described the MMC in the small intestines of fasting dogs. He thought it might be a movement that cleans the digestive tract between meals [6]. Going back further to 1912, there was an experiment by physiologist Cannon and graduate student Washburn. Washburn swallowed a tube with a balloon attached. When he felt hungry, he pressed a key. It is reported that the stomach contractions were recorded at the same time he pressed the key, matching the records well [8]. This experiment is known as an example showing a link between the feeling of hunger and stomach movement. However, the original paper has not been verified directly. Also, we cannot say that hunger is determined only by stomach contractions.
5. Is a Stomach Growl Always a Sign of Hunger?
The growl is a sound that stands out when you are hungry, but it is not only that kind of sound. It happens during and after meals, and it can also occur during the periodic contractions when you are not eating [3]. Stomach noises are generally considered normal digestion sounds, and there is usually no need to worry. However, if you have stomach pain, or if the sound or its frequency concerns you, it is advised to consult a doctor [1]. This article is not intended for diagnosing symptoms. If you have concerns, please talk to an adult or a doctor.
6. A Home Experiment and Topics to Look Up About Stomach Sounds
If you want to investigate this yourself, you can try a simple experiment at home. Get two empty boxes. Leave one empty and fill the other with towels. Tap them gently with your fingers and listen to the difference in sound. This helps you imagine how "contents soften the sound." However, this play does not prove that the same thing is happening inside your stomach. You can also visit a library and look for books on the human body or digestion. Compare how they describe peristalsis and the MMC. You can also read explanations about the digestive system from medical institutions or public agencies. If you are worried about stomach noises or your health, consult a doctor with an adult.