You might not absorb all of the calories if you purge, but you do get some of them. Binging is still going to affect your intake, even if you purge (by any of the methods). The same is true of meds. Sometimes people think that if they take meds and then vomit, the meds don't enter the system, so they might take more meds. It depends on the form of the medication, but some of it does get absorbed and people have accidentally overdosed because they kept taking more of a pain med or other med when they threw up.