Gardner won gold at the 2000 Olympics by beating a Russian who hadn't lost in 13 years. Gardner's challenge to all comers now: Finish the burger plus a basket of fries and a 44-ounce drink in 20 minutes.
The Casper Star-Tribune reports Gardner's best is 8 minutes, 23 seconds.
Gardner is competing to lose weight on the NBC show, "The Biggest Loser." He weighed in at 474 pounds, more than 200 pounds heavier than when he won gold.