1 of 12
Admit it: 48 never looked this good! The Aussie model, known around the world as "The Body," ignited bikini envy from a whole new generation of beachgoers when she flaunted her fit form in the pages of PEOPLE. "I do get jitters," says Macpherson of donning a two-piece 20-plus years after gracing four Sports Illustrated covers. "I was comfortable [at the shoot]. But I had to get my self-conscious 'maybe I don't look my best' head out of the way and go with, 'Let's celebrate where I'm at.'"
2 of 12
The 35-year-old True Blood star, who will bare all in the upcoming stripper flick Magic Mike, worked out with Hugh Jackman's trainer Ron Matthews, who gave the actor a program of low-weight, high-rep, cardio-intensive workouts. "I didn't want to be like one of those statuesque eighties action stars," he told Details magazine.
3 of 12
The dancer-turned-actress, 23, enlisted the help of celeb fitness trainer Marco Borges, who pushed Hough during rigorous 2-hour workout sessions at least 5 days a week. "We were doing everything from stand-up paddleboarding…to doing 5-mile runs to doing 50 stories in a building," Borges told PEOPLE of the Rock of Ages star's typical routine. "She's very driven and self-motivated."
4 of 12
The Australian actor, 28, said he never lifted weights until he trained for 2011's Thor, for which he packed 20 lbs. of muscle onto his 6'3" frame. Though weight training was "all pretty new" to Hemsworth, the athletic star grew up surfing, boxing and playing Australian Rules Football (a mix of soccer and rugby).
5 of 12
6 of 12
"Girls have come up, ripped my T-shirt and all that stuff," Levy told PEOPLE – and we secretly don't blame them! The telenovela star, 31, gave audiences even more reason to tune in to Dancing with the Stars – to see salsas, sambas and some major washboard abs. "I have never heard it that loud in there," pro partner Cheryl Burke said of Levy's ballroom appeal.
7 of 12
8 of 12
9 of 12
When Efron signed up to play a marine in The Lucky One, the former Disney heartthrob put on more than 18 lbs. of muscle with a protein-packed diet and exercise regime. "By the end of the movie I didn't recognize myself," Efron, 24, told Men's Health. "You hear about guys like Christian Bale who dive into it and are really able to transform. I've always wondered if I had the willpower to actually do it. And I'll always have pride around the sense that I can."
10 of 12
"As I aged I noticed that my face looked a little fuller or I had a little backfat," the Think Like a Man star, 39, told PEOPLE of how her body changed with age. "It had a lot to do with junk food and fast food. I've started to read labels more. And I'm actually preparing meals like brussels sprouts and meatloaf." But looking super-skinny isn't something Union embraces: "I love looking like a woman," she says.
11 of 12
"It's not about being skinny, it's about being healthy!" says the Extra correspondent and season 14 DWTS standout. Menounos, 33, who was a size 14 during college, stays active with sports, from basketball and running to the Israeli martial art Krav Maga. "I squeeze things in every which way I can," she told Fitness magazine.
12 of 12
12 Stars Who Are in On the Joke — About Themselves
Celeb Quotes of the Day: Natalie Portman, Ashton Kutcher & More