Having done pure liquid diets (with significantly reduced caloric loads) on numerous occasions (not by choice, unlike these fellows) this is mostly true. One will typically see bowel movement frequency drop dramatically, although not entirely to zero in my case.
That said, I am missing a significant length of digestive tract, so my experience may be atypical. I would also note that that as calories increase, to or above your metabolic needs, that this effect would likely diminish.
That said, I am missing a significant length of digestive tract, so my experience may be atypical. I would also note that that as calories increase, to or above your metabolic needs, that this effect would likely diminish.