October 28, 2015 04:13 PM

Ray Kachatorian

Laura Prepon is the first to admit that she used to struggle with her weight.

Despite trying everything from Atkins to appetite suppressants, the Orange Is the New Black star could never seem to find the right food strategy and constantly felt sick to her stomach, which led her to write her new diet and wellness cookbook, The Stash Plan (on stands March 2016).

“When I got to my early twenties, I started having issues with my digestion,” Prepon, 35, tells PEOPLE. “I was gaining weight just when I didn’t need to be, and my energy levels started to plummet. Not to mention I was bloated and puffy most days.”

She continues: “I had just started working on That ’70s Show and was very worried, so I became obsessed with reading diet and health books, looking for answers. I have stacks of them in my house!”

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But her research was just the first step. “I spent thousands of dollars getting my body tested, and nobody could figure out what was wrong with me. This went on for years.”

Fifteen years to be exact. That is, until she met Elizabeth Troy — an integrated nutritionist and co-author of the The Stash Plan — three years ago. “It was one of those kismet things where I knew she was going to heal me and that’s what happened,” says Prepon.

The actress learned that her liver and gallbladder were essentially “stuck,” which meant they could no longer metabolize even nutritious food properly.

Under Troy’s guidance, though, she slowly changed her eating habits. Now Prepon follows the 80/20 rule, sticks to organic, gluten-free food that is non-GMO and swears by bone broth. “As long [the food] hasn’t been altered I’ll eat it,” she says. “I put brown sugar in my tea. There’s nothing wrong with sugar. You have to be able to have fun and live your life.”

Along with this new approach to food, Prepon also adopted Troy’s unique stretching and strengthening technique to improve the function of her organs, specifically her liver and gallbladder. (Similar to acupuncture, it promotes energy flow to the organs.)

“I’m in the best shape of my life,” says Prepon, whose book includes instruction on the targeted stretching that she learned from Troy. “The book is a three-week program to jump start your gallbladder and liver and get them working,”

Courtesy The Stash Plan

“Once we had the breakthrough with the stretching in combination with the food, it legitimately changed everything for me,” says Prepon, who gave up high-intensity gym sessions —”I worked out more than anyone I knew!” — for stretching. “Now it’s the only workout I do.”

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And along with hours at the gym, her weight worries have also disappeared.  “It’s freedom,” says Prepon. “I used to be so tortured. Now I can feel good in my body. I used to be so sensitive that if I ate one morsel of something that was [bad for me], I would completely puff up and feel sick to my stomach with piercing pains. I would joke with my sisters that I had baby tummy. I was like, ‘Am I only supposed to be eat baby peas?’ “

–Michelle Ward Trainor

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