There's a drug called Orlistat, which blocks absorption of fat from the gut. The obvious side-effect is that your poo becomes very fatty and disgusting. Hence

There's a drug called Orlistat, which blocks absorption of fat from the gut. The obvious side-effect is that your poo becomes very fatty and disgusting. Hence the affectionate nickname for Orlistat in the biz: "Orlyshit" (i.e. Oily Shit)