So, what do Rx weight loss drugs actually DO?

BarbieAS

I know, I know, mess you up, etc. I get that. I'm really just curious about the science-y side, like what these drugs do to cause weight loss, and I'm not smart enough to read actual evidence and work it out on my own.

I know there are different ones and that they act differently. From what I've gathered, you've got your appetite suppression options and your Alli/Orlistat options, both of which will affect the "calories in" side of "CICO," though obviously in different ways (eating less vs. absorbing less calories from fat). And then something like Qsymia, which seems to have an appetite suppressant component in addition to some other ingredients that I'm not totally sure how they aid in weight loss. So, do any of them actually do anything significant on the "calories out" side (beyond what, like, the caffeine in an extra trip to Starbucks or something would do for you)? Or employ some other process that somehow disrupts the standard "calories in - calories out" nature of weight loss?