Seeing the disappointment on his daughter's face because, at 400 pounds, her dad couldn't play with her, was the fuel one father needed to turn his life around after 25 years.

"I probably wouldn't be here if I didn't smarten up," David Murphy, 47, told Fox News. "So, instead of waiting to walk her down the aisle, she probably would have been walking me down the aisle."

In 1994, Murphy was attacked by three men and stabbed 13 times, with one wound just missing his heart and puncturing a lung. It took him seven months to recover from his injuries, including relearning how to walk after losing half of a calf muscle.

DAUGHTER'S DISAPPOINTMENT FORCES DAD TO CHANGE HIS LIFE:

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"I used that as an excuse to be lazy," he said. "Over the years, I ate a lot and drank a lot and put on a lot of weight."

Over the next two decades, Murphy gained 200 pounds, drank nearly every day and struggled with PTSD from the attack. 

david murphy weight loss

David Murphy lost 170 pounds and overcame his PTSD after suffering in silence for 25 years. (Courtesy of David Murphy)

"I hid it for almost 25 years — from friends, family" he told Fox News.  "I looked like the happy guy at the pub. But I was drinking to escape.

"And then she came along."

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The birth of his daughter, Chloe, in 2014 sparked a desire to turn his life around. Murphy went to a nearby gym. But just 20 minutes after getting on a treadmill, he heard two men mocking him, saying the back of his neck looked like "a pack of sausages." Crippling anxiety stemming from his PTSD prompted him to give up and go home.

Four years later, in 2018, Murphy was leaving a playground with Chloe when she asked him to race her home. 

"I said, ‘Sorry sweetie, you know dad can’t run,’ and the look of, not just sadness, but disappointment. I'll never forget it," Murphy said. "That lit a fire in me."

He posted on social media that he would lose 100 pounds in a year and pledged to donate $1 per pound to Can Praxis, a charity for veterans and first responders with PTSD

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He started boxing, eating healthy and stopped drinking. Murphy eventually lost 170 pounds and got his PTSD under control.

"Now, we race all the time, and she’s smiling all the time," he said of his daughter.

Once Murphy reached his 100-pound goal, people began matching his charity donation. 

"My $100 turned into over $20,000 for those charities," he told Fox News. "I wouldn't be here if it wasn't for first responders. So, I like to pay them back."

Murphy talks about his journey on social media and on his personal blog. His inbox is flooded with hundreds of messages from fathers who are struggling just like he was seeking advice. 

david and chloe murphy

David Murphy, 47, said his daughter, Chloe, 8, is the reason he remains motivated to stay healthy.  (Courtesy of David Murphy)

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"I know I can't reach everyone," he said. "I still have tons of messages to try and go through, but I'll get through them." 

Almost five years into his transformation, Murphy said Chloe remains his motivation every day. 

"I used to sometimes sit around and wonder what my purpose was and why I was kept around," he said. "And then I look at her and that's pretty clear." 

To watch the full interview, click here