Do probiotics make you poop more? If so, why?

I don’t know if you mean “you” as in me or as in the general “you.” I don’t know what they’re supposed to do for people exactly, but I can definitely say they work ass-backward on me. They give me the runs and yeah I end up pooping a lot more. But then my digestive tract is anything but normal.

Other people have much nicer results from them, I think.

No, just more regularly.

About 60% of the dry weight of an average person’s feces is composed of bacteria. So it would follow that a person whose intestinal flora had been wiped out (e.g. by antibiotics) would produce less poop. Reestablishing the bacterial population with probiotics would ratchet up the poopage.

”...ratcheting up the poopage”. Now, there’s an image.

Not that I’ve noticed.

But I’m giving you a GQ for your details. :)

Just to add this: The population of bacteria in your gut will be self-limiting. It can’t grow beyond what can be supported by the amount of food you send its way. So if your gut already has a healthy flora population, then it will already have pretty much all of the flora it can support down there. Taking probiotics in that case may change the makeup of the population, but not the overall biomass, so no extra poop.

It depends on your health when you start. It usually makes your stool more consistent, less firm if you are the hard constipated type, but more collected is you are the loose watery type.