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(CNN) -- Jonathon Walters didn't know where to begin. He just knew he had to start somewhere, or he wouldn't be alive for much longer.
His weight had caused him problems for years. In high school, he was wearing size 50 pants. As a junior, sick of the bullies and comments from teachers, Walters went to his father and told him he was dropping out of school.
He recalls his dad saying, "John, quitting is unlike anything else in life. It is only hard the first time you do it. After that it is habit and almost impossible to break."
His dad was right. Walters received his high school diploma through home schooling in 2006. But in the years that followed, he quit college and multiple jobs.
Now, though, the comic book colorist from Benton, Illinois, is finally sticking with something. His father's death motivated him to lose 200 pounds in the last nine months, and he says he isn't looking back.
'My world had collapsed'
On May 6, 2013, Walters received devastating news: His father had died from a heart attack. He was 53.
According to Walters, his father wasn't overweight or really out of shape, so his death was unexpected.
"My world had collapsed," Walters said.
Walters was despondent. He left his job as a telecommunications sales rep and didn't speak to practically anyone besides his wife and three young boys.
Already heavy, Walters began packing on more weight in the weeks after his father died. He ate to numb the pain he felt, every night feeling the crushing weight laying heavy on his chest.
"At first I played the role of the victim and slowly let my obsession with food consume me," he said. But then he had a realization about his father's death.
It hit him that he too would "eventually run out of tomorrows." On July 18, he woke up and decided he had had enough. He was done.
"I was done being a burden to my family. I was done feeling pain every second of every day. I was done being stared at in grocery stores. I was done being the regular customer at fast food restaurants. I was done being the unhealthy version of me.
"I was done quitting everything I started. I was going to not only lose the weight, I was going to obliterate it. I was going to stop giving up. I quit quitting."
Walters made a doctor's appointment for the next day. He had no idea how he would do it, but he was determined to lose weight without surgery and knew he needed help. At the doctor's office, he had to sit in the bench-style chairs because he was too large to fit in the regular seats.
Facing reality was hard. He weighed 477 pounds, had high blood pressure and high cholesterol, as well as a severe fatty liver.
He left the doctor's office and started exercising the next day.
"I could barely walk without getting winded. After every time I went walking, I could feel pain in my legs and feet. It hurt so bad to keep going, but I knew it was temporary and giving up was permanent."
Walters would walk a quarter mile, then rest for 5 minutes. Slowly, he worked himself up to greater distances. Soon, he was up to 3 miles a day and was down 50 pounds.
A few months later, he started running. Walters now runs 10 miles a day, lifts weights and works out on machines at the gym. He has completely changed his diet, lowering his carbohydrate intake, eating more vegetables and fruits, and increasing his protein consumption. He also cut out fried foods and soda.
The 6'3" man currently weighs 270 pounds. He still wants to lose an additional 30 to 40 pounds, but at a much slower pace through weightlifting. He started a Facebook page to hold himself accountable and is inspired by all the messages he gets each day.
Terri Hartman, a nurse practitioner who worked with Walters early on in his diet, said she's thrilled with his progress. Besides changing his own life, she's seen his lifestyle changes inspire others, including his two sisters, to become healthy. Walters has found new strength and willpower, Hartman says -- something that will aid him the rest of his life.
This time, Walters is determined not to quit.
"It isn't about me anymore. My mission is to bring motivation to the masses and show them it doesn't take any surgeries, pills or other products," Walters said. "I have three boys and a wife that count on me daily. ... Imagining my sons and wife without me, makes every ounce of effort I put in worth it."