I lived in Japan for a year and for some reason, eating competitions were quite often shown on TV, so over there it's really popular entertainment. The best competitors (like the skinny guy who always wins the hot dog competition) are celebrities, and I wouldn't be surprised if they actually make a living of it professionally.
I watched one show where they followed some of the best eaters, (and none of them were fat) and besides their eating training, they did a lot of cardio training as well. They were as serious about it as professional athletes (only in Japan)
But I guess you need to be in good shape for your body to cope with something so extreme, if you want to stay alive.