What causes bloating and distension?

You might think that bloating and distension would be due to excess gas. But more likely the discomfort is due to irritable bowel syndrome and the distension is the result of relaxation of the muscles of the abdomen and diaphragm (the muscle that separates the abdomen from the chest). Scientists have measured gas content and abdominal size in people who have bloating and distension and have not found that people with these symptoms have more gas than people who don't.

Abdominal wall strength or function seems to play a role. For example, abdominal muscles relax during meals to accommodate large volumes of food. In distended patients, the abdominal wall may relax to an abnormally exaggerated degree and the diaphragm may drop, causing further distension. Think of the opposite of the typical upright military posture which requires sucking in abdominal muscles and diaphragm to pull in the stomach and thrust out the chest. In patients with distension, the diaphragm drops, abdominal muscles sag, and waist abdominal circumference grows. Excessive descent of the muscles of the diaphragm, which separates the chest from the abdominal cavity, may also play a role.

There are no surefire treatments for bloating and distension, but because it often goes hand in hand with irritable bowel syndrome (IBS) patients, it is treated the same way.