Alan Faneca weighed more than 300 pounds during his 13-season career as an NFL guard, with nine Pro Bowl appearances.
Faneca has dropped 100 pounds in the two and a half years since retirement.
Faneca ran his first marathon in 3:56:17.
“I was very nervous about going from the slow long run pace to all of a sudden running 30-45 seconds faster,” he said. “I got the adrenaline thing but adrenaline doesn't last for four hours.”