(NSFW?) What makes up...#2?

…for lack of other SFW euphemism.

What exactly goes into human faeces? (In UK now, using British spelling.) Theoretically, would someone “use the loo” less if their diet included very little waste? I know insoluble fiber, found in veggies, is poo glue, so if you cut it out it must decrease the volume, right? And a lot of things must exit via the urea route rather than the faecal route.

So, what are the main ingredients in human waste? Other than corn and flax seeds, which I think we can all recognize :)

Thanks!