Biggest Loser's Jillian Michaels wasn't always in such good shape.
The 36-year-old admits to the July issue of Redbook (on stands June 22) that she weighed 175 pounds at her heaviest.
"Being big as a kid was pure hell," says the 5-foot-2 1/2 trainer, who began to pack on pounds at age 12 after her parents announced their divorce. "I spent all of eighth grade in my classroom because God forbid I ever left. I was terrorized."
Michaels had a troubled childhood, and entered therapy at age five.
"I was a really disturbed kid," she says. "You know how kids have night terrors? Mine were really bad. I thought sharks were coming out of the drain in the bathtub. I couldn't sleep at night, every night, waiting for aliens to come. I'm not kidding you: I. Was. Traumatized. And mom got me into therapy."
But she began really getting into trouble once her parents split after 18 years of marriage.
"They were kind of midlife-crisis-ing, and I was sort of the afterthought. I became pretty angry — no one wanted to deal with me — so when I was 17, my mom was like, 'You're not living here.' We were fighting," Michaels says of being kicked out of her home.
Deeply depressed and overweight, Michaels began doing martial arts. "Karate saved my life. It all stopped the day I broke two boards with a kick," she says.
From there, she eventually became a certified fitness trainer, and auditioned for The Biggest Loser at 30. Now, she stars on her own show, Losing It With Jillian, writes books, stars in exercise DVDs and acts as a spokeswoman for nutritional supplements.
"I learned a lot being on my own," she explains. "I grew up. I had to make money. I learned how to make decisions that are right for me."
The demanding trainer says the biggest misconception about her is that she's a "b-tch. I really don't have a mean bone in my body! Do you know how easy it would be to tell people what they want to hear? It would be heaven! But, unfortunately, it doesn't get the job done."
Now, she's proud of her success and svelte figure — but has skipped every high school reunion to avoid the kids who mocked her.
"Honestly, that's why I'm always with the underdog, because I'm always avenging that underdog part of myself," she says.
Her ultimate goal?
"I could never answer that without looking like a total monster. OK, [bleep] it: I would like to win a Nobel Prize," she jokes. "In a perfect world I'd like to get to that place where I walk away from everything. And then I can be pure Bill Gates. Cure smallpox. I want to turn around and be like, 'I cured smallpox. How about those apples?' You know what I mean? Or, like, "I reversed global warming. How 'bout that?"
For access to all our exclusive celebrity videos and interviews – Subscribe on YouTube!