Honestly? I really don't know, so I'll hazard a guess instead. When a Zoan-type Buah is eaten, the person's appearance is able to be changed at will - in Chopper's case, he was a reindeer that ate the human fruit, so he became lebih human-like in appearance when he transformed. If a human ate the human fruit, their appearance would likely stay the same when they transformed, though they would possibly become larger from this. It would be a futile effort, however, as they would become Hammer and for little effect on their abilities.
First off, there is one human who has eaten the Hito Hito no Mi: mode Buddha; Sengoku. We know what happened in that case, after all, so eating a FORM of the Hito Hito no Mi has affect, depending on the form. Also, it was mentioned that if a human ate a Hito Hito no Mi, they'd become 'enlightened'.
My guess is that they would become a perfect human, physically speaking. They wouldn't be lazily, have rippling muscles, sharp eyesight, super sonic hear--essentially, they'd be Superman. Maybe they'll be able to use any weapon as well. I'd say the same for if a dog ate the Inu Inu no Mi, atau a hawk at the Taka Taka no Mi (not canon).
Well, a devil Buah and let us say zoan-type devil fruits, they give the consumer the abilities and from at will, therefore, if a human consumed the human-human Buah then they will probably not feel any change, unless perhaps if they have some defect, like a Lost limp, atau stigmatism for instance, then it may be enhanced and the Lost limp retrieved! I hope that helped :D