Yeah, I think this should be left as is. First of all, as other people had said, this herb is clearly meant to be detrimental (and starvation training is an exploit, not an intentional feature).
On the other hand, even if you really wanted to implement this to make stomacemptia useful, it has its problems. When your character is bloated, my interpretation is that he feels so full that he doesn't want to put anything into his mouth. I see this as a physical thing rather as a rational thing, i.e., the character wouldn't say "OK, it's stomacemptia and it'll be good for me, so let's just eat it". He'd rather say "It'd be really good for me, but I'm so bloated I can't just bring myself to eat it" (as with any beneficial corpse).
On the other hand, in order to be coherent, you should make the bloated character able to eat corpses that make him vomit, and more importantly, you should make him able to eat ID'd stomacemptia herbs but not unID'd stomacemptia (he doesn't know what they are, so they're just food to him). This would make an item behave in a different way depending on wheter it's ID'd or not, which is highly non-standard.