Watching YouTube fitness star Cassey Ho smile as she does a million squats (at least that's what it feels like if you've tried her most popular video, Call Me Maybe Mighty Squat Challenge
), you would never guess she grew up chubby.
"There were some mean kids back then, and that affected me," says the bubbly host of YouTube channel Blogilates
, which has 1.3 million subscribers. "I became conscious of my body at a young age."
But it wasn't until high school that Ho discovered fitness – from an infomercial. "I was 16, and Mary Winsor was on TV trying to sell her Pilates DVD. And I was like, 'That's really cool!' So I asked my parents to buy me the DVD and absolutely fell in love."
Now a certified Pilates instructor herself, L.A.-based Ho, 27, is helping viewers tone, tighten and toughen up – for free. Her Blogilates channel includes workouts for nearly every body part. "It's honestly all based on what my fans want," she says. "Whatever they want, that's what I do."
Ho didn't plan on becoming an online fitness phenomenon. "I started the YouTube channel about five years ago when I moved to Boston for my first corporate job after college as a fashion buyer," she says. To stay in touch with her Pilates students, "I'd put up a video for them so they could work out. But as it turned out, people all over the world started watching."
In addition to her YouTube channel, Ho has started an online Blogilates fitness community
, which features exercise plans, recipes and motivating blog entries. She also designs and sells her own workout gear, making good use of her fashion background.
But her true passion is health and fitness. "It makes me feel good internally in a super happy type of way," she says. "When you feel good, you feel that you look good, and then you perform even better. It's an amazing cycle."
What advice does she have for people who may have trouble getting that cycle started? "Find something you think you may be interested in and give it a shot," suggests Ho. "The most important thing about living a healthy lifestyle is picking something that you don't think is a chore."
To learn more about the hottest workouts on YouTube and feast your eyes on Hollywood's Most Talked About Bodies, pick up the latest issue of PEOPLE, on newsstands Friday