I have found since my gallbladder was removed(2010), that I can’t tolerate high fat consumption, else I get what I affectionately call the ‘Xenical effect’. I put this down to not having that little reservoir of extra bile, normally stored in your gallbladder, ready to help digest any fatty meals, so unable to digest the high fat content, my body just rejects it – the very next day in a rapid way :). I just have to watch the fat content of food and not over indulge in cake and cream(worst offenders). Not all bad I suppose as I won’t gain any extra weight, but it does mean I have to have half portions of cake and go easy on the cream and chocolate. At least I can eat, albeit smaller portions, of those foods I couldn’t when I had gallstones.
I have a more of a tummy now but I think this is more age(perimenopausal) and after two kids, plus surgery, rather than just surgery alone – my tummy muscles had disappeared after the second child 🙁
Maybe try cutting down the high fat content foods may help with the diarrhea, certainly helps with me. You don’t have to stop them altogether, I find just maybe having half the portion of something fatty helps, though try to stick to less than 5% fat is best of all.
Hope that helps x”