The next Saw movie should be all about fatties.  "I want to play a game. The room you are in will slowly contract and crush you over the next 72 hours. The room is equipped with carbon dioxide sensors and the door will only unlock when they have sensed you have lost 10 pounds of fat through respiration. Fresh meals from McDonald's will be constantly available but 3 times any amount eaten is added to the required weight loss for the door to unlock."