Stand sideways in front of a mirror at 8 a.m., then again at 4 p.m. For many women with bloating, the difference is obvious: a flatter morning belly and a rounded afternoon one. The natural assumption is that the belly has simply filled up with gas.
Research from a group in Barcelona suggests that's only part of the story. In people with functional bloating, how far the belly sticks out depends a lot on how the muscles of the trunk respond, not just on how much gas is inside. That's useful to know, because muscles, breathing and posture are things you can influence.
A bloated belly may not hold much extra gas
In one study, researchers took CT scans of 56 people whose main complaint was bloating, first on a normal day and then during a severe bloating episode. In the 47 people with a functional gut disorder like irritable bowel syndrome, the front of the belly pushed out by about 14 mm, yet the total volume inside the abdomen rose by only about 0.3 liters. At the same time, the diaphragm, the dome-shaped breathing muscle under the lungs, had moved down (Accarino et al., 2009).
People with a diagnosed gut motility disorder looked different. Their abdominal volume rose by about 1.4 liters during bloating. In the functional group, though, the scans pointed to the belly's contents being shifted down and forward rather than a large increase in gas.
When the diaphragm works against you
In a follow-up experiment, the same research group gave a gas load to the colon of 20 people with bloating and 15 healthy volunteers. In the healthy volunteers, the extra gas relaxed the diaphragm and slightly increased tone in the front wall of the belly, which helps the abdomen make room. People with bloating did the opposite: their diaphragm contracted, and one of the deep abdominal muscles relaxed, so their bellies expanded more with the same amount of gas (Villoria et al., 2011).
Researchers call this abdomino-phrenic dyssynergia, which is a mouthful that means the diaphragm and belly muscles aren't coordinating. It's an involuntary response, not something you're doing wrong.
The response can be retrained
In a later study, 45 patients with visible belly distension, 42 of them women aged 24 to 71, were scanned and monitored with muscle sensors. During distension, the diaphragm contracted and dropped by about 12 mm, the muscles between the ribs contracted, lung volume rose by about 500 mL and belly girth grew by about 32 mm (Barba et al., 2015).
Fifteen of these patients then had a median of two biofeedback sessions, in which live readings from muscle sensors guide the person toward a different breathing pattern. Afterward, activity in the diaphragm and the muscles between the ribs fell, a deep abdominal muscle became more active, and girth decreased by about 25 mm. A control session before treatment didn't produce the same change.
The American Gastroenterological Association's 2023 clinical practice update lists diaphragmatic breathing as one of the approaches used for this pattern (Moshiree et al., 2023).
Where everyday posture fits in
Body position also changes how gas moves. In eight healthy volunteers who had gas infused into the small intestine, gas moved through much more easily when they were upright than when they lay on their backs. After an hour, about 13 mL was retained in the upright position, compared with 146 mL lying down (Dainese et al., 2003).
These studies don't prove that changing your posture will stop bloating. But they point to a few reasonable habits:
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Stay upright after meals. Gas moved more slowly lying flat than upright in the study above, so sitting up is a better choice than sprawling on the couch right after dinner.
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Notice your breathing when you feel bloated. If your chest is lifting and your belly is pushing out, try a few slow breaths with a long, relaxed exhale instead of bracing.
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Keep moving. Gentle activity, like a short walk, is another easy way to keep gas moving.
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Consider guided help. Clinician-guided biofeedback is not the same as breathing exercises at home. If visible distension is a daily problem, ask your doctor whether a gastroenterologist or a specialized physical therapist could help.
A simple breathing reset
- Sit tall in a chair with your feet flat and your shoulders relaxed.
- Rest one hand lightly on your chest so you notice if it starts to lift and tense.
- Breathe in slowly through your nose without forcing it, keeping your chest and shoulders quiet.
- Breathe out slowly through slightly pursed lips, a little longer than the in-breath, and let your belly and ribs soften.
- Repeat for 3 to 5 minutes, especially in the afternoon or after a meal.
This hasn't been tested the way clinical biofeedback has, so think of it as a low-risk experiment rather than a proven fix.
When to get checked
Most bloating that comes and goes isn't dangerous. But see a doctor if bloating is new and happens most days, especially with early fullness, pelvic pain or urinary urgency, or if you have blood in your stool, unexplained weight loss, anemia or symptoms that wake you at night. You can also read more about why the gut changes after 40.
Sources
- Accarino A, Perez F, Azpiroz F, Quiroga S, Malagelada JR. Abdominal distention results from caudo-ventral redistribution of contents. Gastroenterology. 2009;136(5):1544-51. PMID 19208364
- Villoria A, Azpiroz F, Burri E, Cisternas D, Soldevilla A, Malagelada JR. Abdomino-phrenic dyssynergia in patients with abdominal bloating and distension. Am J Gastroenterol. 2011;106(5):815-9. PMID 21540894
- Barba E, Burri E, Accarino A, et al. Abdominothoracic mechanisms of functional abdominal distension and correction by biofeedback. Gastroenterology. 2015;148(4):732-9. PMID 25500424
- Moshiree B, Drossman D, Shaukat A. AGA clinical practice update on evaluation and management of belching, abdominal bloating, and distention: expert review. Gastroenterology. 2023;165(3):791-800.e3. PMID 37452811
- Dainese R, Serra J, Azpiroz F, Malagelada JR. Influence of body posture on intestinal transit of gas. Gut. 2003;52(7):971-4. PMID 12801953
This article is for general information and isn't medical advice. Talk to your healthcare provider about bloating or visible distension that is new, frequent or getting worse.
