Super Size Me (2004)
Super Size Me is a 2004 American documentary film directed by and starring Morgan Spurlock, an American independent filmmaker. Spurlock's film follows a 30-day period from February 1 to March 2, 2003 during which he ate only McDonald's food. The film documents this lifestyle's drastic effect on Spurlock's physical and psychological well-being, and explores the fast food industry's corporate influence, including how it encourages poor nutrition for its own profit.
More at Wikipedia.