Credit: Eric Ray Davidson for DETAILS

It's no secret that Adam Levine has a hot body. What is surprising is that the 32-year-old Maroon 5 frontman hasn't lifted a weight or been to the gym in five years.

"Weights made my neck thick, and I would be like, 'I'm turning into a monster!'" Levine tells the December/January issue of Details. "Yoga takes what you have and molds and sculpts it, which is a much more natural way to look and feel."

Though yoga is relaxing, Levine also realizes that it's helped transform his body. "I don't like how people bullsh-t about how yoga is not about vanity," he says.

Before Maroon 5 takes the stage, Levine can usually be found in a room backstage marked YOGA. "Playing a show before thousands of people is a highly unnatural state," he tells Details. "When I get on the mat and do an hour of yoga before the show, I come out physically relaxed."

The Voice mentor works with New York City yoga instructor Chad Dennis, who Levine says "will take me on a friggin' obstacle course of yoga." The payoff? "It's an investment in happiness for the rest of my life."