There are some restaurants offering you so-called "challenge menu". When you eat up extremely big potion of food, you don't have to pay at all or in some restaurants, you even get some money after doing it.
When you're a big eater like Takeru Kobayashi, go to a Chinese restaurant, kagurazaka hanten in tokyo. You can choose one from following 4 menus.
2.5 kilo fried rice,
3 bowls of jumbo ramen noodle,
100 pieces of gyoza,
or one 2.5 kilo jumbo gyoza
in 60 minutes.
If you fail to eat them up, you've got to pay the fine.