I use lamb fat as my main fat source and also use coconut as my main carb source. Too much lamb fat does make for loose and oily stools. Overall I find that if I eat enough red meat with the lamb fat my digestion is great. I have had severe fungal issues and it seems that a high fat diet with coconut, lemon water, egg yolks, high meat seems to cleanse as well as nourish.
I have never tried to do just fat.