I've got a project, though it's secondary to the main novel I'm working on, that does involve weight gain to an extent; it's a sci-fi premise in which a certain synthetic drug is put into circulation as a contaminant in certain street drugs, primarily heroin. This drug has a latency period, but eventually it causes a person to either gain or lose weight at a supernaturally impossible rate, depending on which variant on a certain gene the person is. Extreme weight gain, weight loss, feeding, anorexia, etc. are going to be major themes in the book. I've only got a couple of chapters at the moment, but once I've got it more fleshed out and have more to offer I wouldn't mind making it available if anyone is interested. It does involve the feeding fetish/FA to an extent, but it is not quite the primary focus of the story.