Film records effects of eating only McDonald's for a month 25.01.2004 12.00pm - By DAVID USBORNE NEW YORK - Normally sane actors have been known to gain or lose huge amounts of weight for their art. Think of Renee Zellweger in Bridget Jones's Diary. Directors, of course, never have to undergo such torture. Or so it used to be, until Morgan Spurlock had a bright idea for a film project. The first clue to his particular misery comes in the title of his documentary, which has become the darling of this year's Sundance Film Festival. It is called Super Size...