Gaining

Feederism is a growing fetish, pun intended, so I think with more and more feeders and feedees growing up and going through college many are bound to end up in the sciences, and a few will almost certainly end up going into medicine or biochemistry. So I don't think it's too far fetched to think that something like this could, eventually, appear. Though I doubt it'll be widely marketted because of the relatively small niche that would be actually interested in it.

Yes, the laws of conservation of mass and energy make it a bit trickier to make something like this but that doesn't mean that an instantly fattening serum or shake won't be created. That was more along the lines of what I was thinking about in my earlier post anywho.