People who find themselves consulates, irregular, or have to strain when they go should consider more fiber.
It doesn't, it can't. From paper "Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms" - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3435786/ :
"Whilst it is often stated in physiology textbooks that bulking agents improve peristalsis, there is no proof of this in practice nor experimentally. Regardless of the food ingested, small intestinal and right mid colonic contents are fluid and all ingestible dietary fiber is suspended therein. Dietary fiber, therefore, cannot act as solid boluses for the initiation of peristalsis. In fact, dietary fiber had been shown to retard peristalsis and hold up gaseous expulsion in human experiments[22]."
> "People who find themselves consulates, irregular, or have to strain when they go should consider more fiber."
They should consider less fiber; from the same paper:
"Dietary fiber is also associated with increased bloatedness and abdominal discomfort[22]. Insoluble fiber was reported to worsen the clinical outcome of abdominal pain and constipation[18-20]. In our recent study, patients who followed a diet with no or less dietary fiber intake showed a significant improvement, not just in their constipation, but also in their bloatedness. Patients who completely stopped consuming dietary fiber no longer suffered from abdominal bloatedness and pain.[...]"
"Stools only become well-formed in the sigmoid colon and rectum and by this time, especially in constipated subjects, more stools result in more evacuation problems. It is not logical to increase both the volume and size of stool in patients with idiopathic constipation and indeed for anybody with difficulty in passing stools, e.g., due to anismus or anal spasm from anal stricture, fissure or pelvic outlet disorders. We have shown that decreasing the bulk and volume of feces immediately enables the easier evacuation of smaller and thinner stools through the anal sphincter mechanism. This eliminates the need to strain in passing stools, and prevents the tearing of the anal sphincter and bleeding due to large and bulky fecal loads. None of our patients experienced anal bleeding or straining following complete abstinence from dietary fiber."
"The results of this study should lead us to reexamine popular beliefs in benefits of dietary fiber and more studies should be undertaken to confirm or repudiate these results."