Judging by one of the areas, more like water inflation (maybe milk inflation, too, since lactation is one of the depicted themes--there would be no shortage of it as the protagonist is made to lactate and there are cows to milk)...
That being said, I would put it in the same category as food stuffing. In fact, I'd combine the two and then increase the experience points required to expand the stomach and/or add more levels (currently stops at 15)--maybe it should ultimately fatten the entire body...
Food for thought! (Pun...intended!)