Sharee Samuels had always been of average weight as a child, but at 13 she was on her own after school. She gorged on chips, pretzels and cookies.

"When I started weighing myself at 13, I never saw below 200," she said. "I had unlimited access to anything I wanted. I no longer had parental control over my food."

She used to hide food so her parents wouldn't find out how much she was eating, and in her senior year of high school, her weight peaked at 256 pounds.

Courtesy Michael Holcomb

Michael Holcomb can probably relate. When he was 13 years old he tipped the scale at nearly 500 pounds, and when he graduated he gained another 100 pounds.

"I didn't do much, and what I did do was eat. So I played video games, I would watch TV and I ate, and I was good at it," he said.

But Samuels and Holcomb are no longer obese.

Samuels and Holcomb are both featured in People magazine's special issue that focuses on people who'd lost about half their body weight. They both appeared on "Good Morning America" to share their weight-loss strategies.

For Samuels, a graduate student and Zumba teacher from Federal Way, Wash., one on of her lowest points was having to shop with her mother because, at 17, she couldn't wear what her friends were wearing.

Three Women Lose Half Their Body Weight

"I had to shop at women's plus-size stores," she said.

After her second attempt at weight loss, she had a breakthrough.

"I was sitting in the car with my mom crying. I felt like I had let my parents down. I had all these resources, two supportive parents and I was just sabotaging myself," she said. "That was the moment I said 'I'm done.'"

She worked with her husband, Andre, to lose weight. She also adopted a vegan diet, and always has healthy snacks available.

Samuels, now 24, lost 121 pounds, and now weighs 135. Her weight loss was so dramatic that she had loose skin removed. Her husband went from 310 to 217 pounds.

Courtesy Sharee Samuels

For Holcomb, 26, the change began five years ago when he was involved in a minor car accident. It got him thinking about his own mortality.

"The next day I [lay] down on my couch and the cable went out, the screen turned black and I was lying there without my shirt and I saw my stomach hanging over the side of the couch, and I broke down and I cried and I promised myself I would change. And from that day onward, I have changed for the better," he said.

When he decided to change his life, he weighed 607 pounds. He now weighs 230, which means he lost 392 pounds.

Just how did he do it? He gave up fatty sandwiches for healthy salads, and started walking. The Escondido, Calif., man now works as a personal trainer.