On this year's cover, Sharee Samuels shows off her new 135-lb. figure, which she earned by walking two miles daily and weekly runs. A former junk-food addict who wore a size 24 as a teen, Samuels admits she would sneak chips and cookies when her family wasn't looking.
"If I was around my parents, I'd eat healthy meals," Samuels says. "But with my friends it was different. I remember a road trip where we ate fast food five times a day."
Now Samuels, 24, follows a vegan diet and loves trying new workouts. "I'd do Zumba with my roommates two times a week in our apartment," says the graduate student.
At her heaviest, Kaitlyn Ekstrom, 31, weighed 263 lbs. But after college, Ekstrom returned home to care for her mother, who was battling cancer. In an effort to make their household healthier, "I did my best to learn how to cook for her," she says.
Ekstrom turned her life around as well. Now 136 lbs. lighter, she is the director of fitness and aquatics at a retirement community in Massachusetts and credits her mom's strength as "a huge motivator."
"When you see someone you love face the fact they might not live much longer with grace, then you realize, 'I can skip dessert,' " she says. "That's such a small thing in comparison."
These ladies join more than 25 other success stories in this week's issue, which includes weight-loss winners who once tipped the scales at more than 400, 500 and 600 lbs., celebrity sidekicks who changed their bodies with the help of a famous friend, and Hollywood's hottest slim-downs of the year.
For more amazing transformations and diet tips that really work, check out PEOPLE's Half Their Size issue, on newsstands Friday