At age 33, Missy Hendricks has spent her entire lifetime at war with her weight.

"My maiden name was Blinkenship and they'd call me 'Battle Ship' and that just stuck in my head," Hendricks told ABC News.

By the age of 20, Hendricks weighed nearly 300 pounds.

When her new husband began to cheat within a year of their marriage, Hendricks turned again to food for comfort.

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"I would eat a whole box of Honey Combs [cereal], the family size, just because I was mad at him," she said. "I felt that I wasn't good enough."

Hendricks divorced her husband but the pain of his infidelity caused her to binge, nearly doubling her weight. Three years later, at age 23, the newly-single Hendricks carried 526 pounds on her 5'8? frame.

"I felt unwanted and I didn't want to be unwanted for the rest of my life, so I had to change," she said.

Hendricks began to follow the Atkins diet and today, 12 years later, she weighs 131 pounds.

While it was divorce that motivated Hendricks to change, it was a wake-up call from a doctor that got Richard Neal to take another look at his health.

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Weighing in at 426 pounds, the 28-year-old Neal, like Hendricks, had been overweight his entire life.

"Even at night, when I was a kid, I would go in and sneak in the fridge and eat packs of hot dogs," Neal said. "I would just binge eat and binge eat until I literally wanted to throw up."

"Eventually I was just eating my worries and pain away," he said.

A doctor told Neal that if his eating habits remained the same, he would not live to see his thirtieth birthday and he would never have kids again.

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Around the same time, a friend loaned Neal a workout DVD that became his tool for transformation.

"I was sitting on the couch," Neal recalled. "I just got done eating a box of cereal and I just thought about that DVD and I was like, 'Hey, I'll try it out.' I had a window air unit and I went and put it on, turned the DVD player on, popped the DVD in and pressed play."

Neal went on to lose more than half his body weight and is now a fitness coach himself.

"This is what I do," he told "GMA" of his career as an independent coach for Team Beachbody. "I help people get their lives back because that's what matters."

Neal, who now weighs 200 pounds, has been able to keep the pounds off by staying focused on his lifestyle, not a quick-fix diet.

"It's all about maintenance," he said. "It's going down to making that lifestyle change because diets are temporary. Lifestyle changes are forever and it's understanding that."

Watch more amazing weight loss stories on "20/20: Half Their Size" Friday at 10 p.m. ET on ABC.