In this video (published March 22, 2018), Dr. Patrick Nemechek discusses a pattern he commonly sees in practice: people with bacterial overgrowth (SIBO) who notice stool changes—especially constipation—after using interventions such as inulin or rifaximin. In his explanation, those changes can be confusing because it may feel like something “caused” constipation when, in his view, it simply revealed what was already there.
Dr. Nemechek frames bowel symptoms through two overlapping influences: bacterial overgrowth and autonomic dysfunction. He outlines how each tends to push bowel function in different directions—and what can happen when both are present at the same time.
Educational note: This article summarizes a short video explanation and reflects Dr. Nemechek’s clinical terminology and framework. It is not a diagnosis and is not a substitute for personal medical care.
How Dr. Nemechek distinguishes SIBO stool patterns
Dr. Nemechek describes one of the most common intestinal features of bacterial overgrowth as loose or more frequent stool. Importantly, he notes that stool does not have to be fully watery to fall into a “diarrhea” pattern—he explains that more frequent stool can still be considered diarrhea in clinical terms. He also gives examples of how some people notice that they eat and then need to use the bathroom right away, and that this can become their “normal.”
In his description, SIBO may also present as watery stool or occasional watery stool. He mentions that certain foods can be a trigger for watery stool in some individuals (he gives tomatoes as an example). In this framework, SIBO tends to push bowel function toward looser, more frequent stool.
Autonomic dysfunction as an “intestinal conveyor belt” problem
Dr. Nemechek then shifts to autonomic dysfunction and how, in his words, the autonomic nervous system controls the intestinal tract. He describes thinking of this system as the body’s “intestinal conveyor belt”—moving contents through the esophagus, stomach, small intestine, and colon.
In his explanation, when autonomic function is not working well, the conveyor belt slows down. He describes potential effects along different segments of the GI tract:
- Stomach: heartburn
- Small intestine: some cramping
- Colon: constipation due to “poor conveyor belt action” and poor emptying
Within this model, Dr. Nemechek summarizes constipation as typically linked to slowed intestinal function related to autonomic dysfunction.
When both problems coexist, bowel habits can look “normal”
A key point in the video is what happens when both forces occur together. Dr. Nemechek explains that if someone has fast, watery stool from SIBO and also slow intestinal function from autonomic dysfunction, those influences can partially offset each other.
In that situation, he says stool function can seem “kind of normal” or at least not overly troublesome. A person might have occasional constipation, followed by looser stool that “fixes things,” making the overall pattern more tolerable and less obviously abnormal.
Why inulin or rifaximin may appear to “cause” constipation
Dr. Nemechek addresses a common observation: after using rifaximin or inulin to help with bacterial overgrowth, someone may notice that their stools become less loose—and constipation becomes more obvious.
In his explanation, this does not mean the intervention created a new problem. Rather, he explains it this way:
- When the SIBO-driven watery/loose stool component improves, that “fast” influence diminishes.
- The underlying autonomic-related slowing can then become more visible—so the person is “left with” constipation.
As he states directly in the video, rifaximin and inulin did not cause constipation in this scenario. In his framework, they made the watery stool portion go away, revealing constipation that was already present underneath due to autonomic dysfunction.
His practical rule of thumb from the video
Dr. Nemechek offers a concise “general rule” based on the pattern he describes:
- Constipation tends to reflect autonomic dysfunction.
- Loose, watery stool tends to reflect bacterial overgrowth (SIBO).
- When both occur together, symptoms may seem more “normal” because one can mask the other.
Timeline: SIBO improvements vs. autonomic improvements
Dr. Nemechek also comments on timing. He explains that once the watery stool portion improves, the remaining autonomic problem is part of the “brain stuff” that takes longer to fix. In his description, constipation related to autonomic dysfunction tends to get better over time as “we fix the brain.”
Medical disclaimer
This content is for education only and summarizes Dr. Nemechek’s statements from a short video. It is not medical advice and is not intended to diagnose, treat, cure, or prevent any disease. If you have persistent diarrhea, constipation, abdominal pain, dehydration, blood in stool, unexplained weight loss, or symptoms that concern you, seek personalized evaluation from a qualified clinician.
