Question 1

What are the main symptoms of SIBO?

Accepted Answer

The hallmark symptoms are bloating and abdominal distension (often worsening through the day), excessive gas, abdominal pain or cramping, altered bowel habits (diarrhoea, constipation, or both), and a feeling of fullness disproportionate to how much was eaten. Systemic symptoms include fatigue, brain fog, nutrient deficiencies (particularly B12 and iron), and skin changes.

Question 2

Can SIBO cause fatigue and brain fog?

Accepted Answer

Yes. Bacterial overgrowth interferes with the absorption of B12, iron, and fat-soluble vitamins, which affects energy and cognition. Bacterial byproducts (including endotoxins) can also cross into circulation and produce systemic inflammation, further contributing to fatigue and brain fog.

Question 3

Does SIBO cause weight gain or weight loss?

Accepted Answer

Both are possible. Methane-dominant SIBO (IMO) is associated with weight gain and constipation, likely due to slowed transit and altered energy harvest from food. Hydrogen-dominant SIBO more often causes weight loss through diarrhoea and malabsorption.

Symptoms

Digestive

Systemic

When to test

Questions about symptoms.

Knowledge is the first step to healing.