The rumbling or gurgling sounds that originate from the abdomen are medically known as borborygmi. Hearing these noises when a meal is nowhere in sight can be confusing, as they are often associated only with hunger pangs. These sounds confirm that the digestive tract is actively working, whether processing a recent meal or performing a regular cleaning cycle. Understanding the mechanism behind these sounds reveals why they are not always a signal demanding food.
How Digestive Noises Are Generated
The growling sound is produced by the movement of gas and liquid through the hollow, muscular tubes of the gastrointestinal tract, including the stomach and intestines. This movement is driven by peristalsis, a series of involuntary, wave-like muscle contractions. Peristalsis occurs constantly throughout the day and night to mix contents and propel them forward.
The noise becomes audible when the contents being squeezed through the narrow passageways are primarily gas and fluid, rather than solid food. When the digestive tract is full of food, the solids act like a natural sound dampener, muffling the churning process. Because the intestinal walls are contracting over an empty space, the sound of the gas and liquid movement echoes and becomes much louder.
The Migrating Motor Complex
The most common reason for loud borborygmi when a person is not hungry is the activity of the Migrating Motor Complex (MMC). The MMC is a recurring electrical and motor activity that sweeps through the gastrointestinal tract during periods of fasting. This process is often described as the gut’s “housekeeper” function.
The MMC initiates approximately every 90 to 230 minutes when the stomach and small intestine are empty. Its purpose is not digestion, but rather to sweep residual food particles, unabsorbed mucus, and bacteria out of the small intestine and into the colon. This cleansing action helps prevent bacterial overgrowth.
The MMC is a powerful wave of contractions, distinctly different from the gentler movements of digestion. The intense muscular activity in an empty environment, partially regulated by the hormone motilin, causes the loud, rumbling noise. Although the brain often associates this intense signaling with hunger because the MMC is only active when fasting, the sound is a byproduct of the gut’s self-cleaning mechanism.
Other Causes of Borborygmi
Borborygmi can also be intensified by factors unrelated to the MMC’s cleaning cycle or true hunger. Swallowing excess air, a phenomenon called aerophagia, is a frequent contributor to increased gut noise. This occurs from drinking carbonated beverages, chewing gum, or eating too quickly. The swallowed air must eventually move through the intestinal tract, creating noise as it passes.
Gas-Generating Foods
Certain foods lead to louder abdominal sounds by generating more gas in the intestines. Foods high in fermentable carbohydrates, such as specific fibers or high-FODMAP foods, are not fully absorbed in the small intestine. They travel to the large intestine, where bacteria rapidly ferment them, producing a large volume of gas that increases the noise of peristalsis. Food intolerances, such as lactose intolerance, similarly cause undigested material to ferment, leading to increased gas production and louder borborygmi.
Stress and Anxiety
The gut-brain axis means that stress or anxiety can accelerate gut motility. This causes muscles to contract faster and more erratically, contributing to increased noise.
When Stomach Noises May Indicate a Problem
While noisy abdominal sounds are almost always a sign of a healthy, working digestive system, specific accompanying symptoms may indicate an underlying issue. A medical evaluation may be warranted if borborygmi are persistently loud or frequent and occur alongside severe abdominal pain or cramping.
Other concerning signs include fever, persistent nausea or vomiting, or a sudden, unexplained change in bowel habits, such as chronic diarrhea or constipation. In rare cases, extremely high-pitched sounds can signal an early intestinal blockage. Conversely, a complete absence of bowel sounds (hypoactive bowels) can suggest a serious slowing of intestinal activity.