Well, looking at the top competitive eaters, they don't seem to be fat at all, so no, it seems pretty unlikely they'll become obese. Choking also doesn't seem particularly likely, because of all the health officials they'd have on hand. If anything, this seems like by far one of the safest sports people do. I mean, it might be terrible for them overall, but not in the ways you mentioned, and hell, given the risks of other sports, it's definitely not the worst.