March 25, 2015 8:36 AM EDT

He may have finished his first 5K of 2015 in last place, but Derek Mitchell gets a blue ribbon for spirit.

The 577-lb. Missouri resident plans to complete at least 12 additional 5Ks this year, giving him plenty of chances to beat his current best time of 1:27:44.

“I made a New Year’s resolution to be healthier, so I stopped drinking soda, I started eating better, and my sister, who is a marathon runner, told me that I needed to actually get out and do some exercise,” Mitchell, 34, tells PEOPLE. “I began by walking a mile a day, and my sister said, ‘Instead of just walking, why not try to attain a goal?’ So her idea was for me to walk a 5K.”

Mitchell signed up for the Big 12 5K in Kansas City, Missouri. While he was walking in the March race, he got the idea to do a 5K each month to stay motivated to keep up with his physical activity.
“Since then, it’s kind of exploded,” he says. “Now I’ve got two scheduled for May, and probably two scheduled for June. I’m pretty much going to be walking one every other week!”

Mitchell has long struggled with his weight as the result of prolactinoma, a noncancerous brain tumor that prevents his body from producing testosterone. Because testosterone controls metabolism, energy and drive, it has been very difficult for him to lose weight in the past.

Still, Mitchell hopes to lose 250 lbs. by the end of the year. He’s been sharing his health progress and goals on his Facebook page, which already has 8,000 likes.

“Now I have so many eyes on me, and because of this following I can’t quit now,” he says.

People from all over the world have asked Mitchell to walk with them at local 5Ks. Much closer to home, he’s inspired his best friend to sign up for his first 5K, and they will be walking April 11’s Rock the Parkway 5K together.

“I want to encourage people,” Mitchell says. “If I can walk a 5K, anybody can. All it takes is just to go out for a walk and get active and get your body moving. Even if you can only walk to the end of the block, walk to the end of the block, because at least that’s something.”

This article originally appeared on People.com

 

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