I am on occasion an office feeder myself (via). Usually for the sorts of non-nefarious reasons that the Jezebel post describes. Maybe this is a real social phenomenon elsewhere, n=1, etc., but I've also never encountered the sort of co-worker who vigorously pushes sweets on me or anyone else. In most offices where I've worked, would-be feeders typically send out mass e-mails to the effect of "Peach cake in the kitchen" and let others take or leave as they choose. (And yes, mostly, people take.)
Also, I'm hard pressed to think of a time when offering a non-body-image-related reason to decline -- such as "Thank you, that looks lovely, but I'm just not hungry right now" or "That looks delightful, but I ate just a little while ago"-- has not been sufficient. I do find it in better taste to avoid mentioning one's diet or weight issues, as all too often, this sort of thing comes off as sanctimonious. It's also difficult for the feeder to back off gracefully, as assenting can signal "Yes, I do think you are actually fat, never mind," which is not really so gracious, either.
Relevant Seinfeld video below also, because nobody's brought it up so far...
Clyde Schechter defends IRBs (from the comments)
50 minutes ago