PHOENIX - Shawn Cannon is on a mission. He's walking his way to a healthier life, one step at a time.

"I'm happy where I am now," Cannon told 12 News.

But that wasn't always the case.

Just two years ago, Cannon, 23, weighed 327 pounds. He was a thin boy growing up, but he was diagnosed with hypothyroidism at age 13. It's a condition where the thyroid gland doesn't produce enough thyroid hormone, which can drastically slow the metabolism.

"I kept gaining and kept gaining all the way until I was 18. And that's where it topped out," Cannon said.

Doctors couldn't figure out how to fix Cannon's thyroid. They tried synthetic replacements, but the medicine didn't work. And Cannon kept gaining weight.

"They couldn't even find a vein in me at all," Cannon said. "They were always poking me and there were bruises all over.

"They wanted to stick cameras and everything up my nose and break my face, telling me -- they needed to crack my skull to see if there was a tumor in there."

At the same time, Cannon's cousin, who was also obese, died from a heart attack. And Cannon was scared for his life.

"I got to a point where I'm done with this. I can't keep going," he said.

So Cannon started to get going. He began walking and cut sugar out of his diet. Plus, his doctors switched him to a natural thyroid medicine.

"I felt better," Cannon said. "I started walking more and the weight started coming off rapidly, like crazy fast."

A year and a half later, Cannon has lost 160 pounds. He's almost half the man he used to be and his old clothes prove it.

"I'm so proud of him," said Karen Cannon, Shawn's mother. " Yes. It brings me tears sometimes just all that he's accomplished and he's doing."

Karen can't believe Shawn now climbs mountains, runs 5K's and dives into obstacle course races. And she's thrilled Shawn's sharing his story on Facebook and inspiring others to be healthy.

"It all comes down to will power, finding it in yourself and not giving up," Shawn Cannon said.

He certainly didn't and now his mission is to make sure others don't either.

Follow Shawn Cannon's journey on his Facebook page here.