SIBO, Gas and Bloating
SIBO, Gas and Bloating
Medically reviewed by:
Dr John Freeman
Gas associated with Small Intestinal Bacterial Overgrowth (SIBO) is often far more painful and disruptive than “normal” gas. This is because gas in SIBO forms in the small intestine, an area that is not designed to store or manage large volumes of gas.
Why SIBO gas feels worse than normal gas
Under normal conditions, gas is primarily produced in the large intestine (colon). The colon contains a high concentration of bacteria, and gas production there is expected. Its wider structure and natural exit pathways allow gas to pass with minimal discomfort.
In contrast, the small intestine:
Contains relatively few bacteria in healthy individuals
Is narrow and lined with sensitive smooth muscle
Is responsible for nutrient absorption—not gas storage
When excess bacteria ferment food in the small intestine, gas builds up in a confined space. This creates pressure that can:
Cause sharp abdominal pain
Push upward on the diaphragm, contributing to acid reflux
Create feelings of early fullness, even after small meals
How gas contributes to gut damage in SIBO
The stretching caused by trapped gas in the small intestine can:
Irritate and inflame the intestinal lining
Damage brush border enzymes, which are essential for proper digestion
Worsen intestinal permeability (leaky gut)
This inflammation further impairs digestion, allowing more undigested food to ferment—creating a vicious cycle of gas, inflammation, and worsening symptoms.
FixBIOME’s clinical approach addresses this cycle by focusing on reducing bacterial overgrowth while supporting digestive function and gut barrier integrity, rather than masking symptoms alone.
Anti-gas (“de-gas”) medications: why they help short-term
Over-the-counter anti-gas products typically contain simethicone. This compound works by breaking large gas bubbles into smaller ones, making them easier to pass.
While simethicone can provide temporary symptom relief, it does not address the underlying cause of gas in SIBO—bacterial fermentation in the small intestine. For this reason, it may be useful in acute situations but is not a long-term solution.
Why you may look “pregnant” by the end of the day
Some degree of bloating later in the day is normal, as digestion can take up to 36 hours. However, bloating that becomes severe, painful, or visibly distends the abdomen is not normal and may indicate an underlying condition such as SIBO.
With SIBO:
Gas is produced in both the small and large intestine
Fermentation begins earlier in the digestive process
Gas becomes trapped without an easy exit
As the day progresses and more food is consumed, gas accumulates—often leading to intense discomfort and visible abdominal distension.
Many people with SIBO experience upper or “full-tummy” bloating, rather than lower abdominal bloating. However, symptom patterns can vary from person to person.
Pimentel M. Gas and bloating in functional gastrointestinal disorders
Rao SSC et al. Mechanisms of bloating and abdominal distension
Quigley EMM. Small intestinal bacterial overgrowth: roles of motility and gas production
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