The protein-rich bounty of the football training table is supposed to grow the biggest and strongest athletes in professional sports. Kansas City Chiefs tight-end Tony Gonzalez was afraid it was going to kill him. "It's the Catch-22," says Mr. Gonzalez, 31. "Am I going to be unhealthy and play football? Or be healthy and get out of the league?"
So last year, on the eve of the biggest season of his career, Mr. Gonzalez embarked on a diet resolution that smacked head-on with gridiron gospel as old as the leather helmet. He decided to try going vegan.