"As the weight kept getting bigger and bigger, I just thought, 'That dream was dead,'" he told Eyewitness News.
Cook was able to cheat death, losing more than 250 pounds. Although gastric bypass surgery helped, changing his lifestyle and way of thinking are what really made the difference.
"I'm on a plant-based diet now. For the last five months, I run, I bike, I swim. I'm training for the Texas Ironman," he said.
He is now carrying about 60 pounds of loose skin, but he says it doesn't bother him one bit -- in fact, it has become part of his journey to encourage others.
"I'm gonna finish the Texas Ironman with my skin just to prove to someone that they can do it," he added.
WHY WE RUN: Houston marathoners' inspirational stories