Leveling Up, by Only Eating!

The main character is stricken by a rare condition that affects only two people in the entire world, bulimic deficiency. He organizes his daily meals to survive, but his hope of survival grows dimmer as the days go by. He consults a doctor, who suggests playing the Alternate Reality Game ‘Athens’, where he can eat as much as he wants without gaining any weight. He plays the game to save his life and become stronger by doing nothing but eating!