The Flab Zone is an area inside of Bowser in Mario & Luigi: Bowser's Inside Story. In this area, Princess Peach gets kidnapped once again, this time, not by Bowser. She gets kidnapped by six Beta Kretins.
In this area, Mario and Luigi must trek through a maze similar to Joke's End in Mario & Luigi: Superstar Saga. There are ten Attack Pieces here which, when collected, grants the player the Jump Hat special attack.
After trekking the maze, the player must put up a difficult fight with the Beta Kretins, who melded together to form the all powerful Alpha Kretin. After destroying it, Peach is saved and the adventure switches to Bowser's role.