1 of 11
Itsy-bitsy bikinis were practically second skin for the former star of The Hills and Laguna Beach, but Cavallari tells PEOPLE, "[It] wasn't until I moved to L.A. – with all the paparazzi – that I became really aware of how I looked." So how does the recently engaged star (to Chicago Bears quarterback Jay Cutler), 24, get the body confidence to rock a two-piece and deal with cameras 24/7? "Everyone is their own worst critic," says Cavallari, who plays up her favorite feature – her legs! – with string bikinis. "Sometimes you just have to take a step back and say, 'Okay, it's actually not that bad.'"
2 of 11
At 42, Aniston has still got it – just ask Spike TV, which awarded the actress with a Decade of Hotness trophy at its Guys Choice Awards in June. But the real honor goes to the actress's yoga instructor pal Mandy Ingber, whom the Horrible Bosses star thanked in her acceptance speech while vowing to "keep downward dogging until the fat lady sings." Amen.
3 of 11
Fans are used to seeing ... ahem, a little more of the Twilight star, 26, in his CK underwear ads – not that he minds. "I won't lie about it," says the actor, who trained and stopped eating candy to shape up for the shoot. "I started getting text messages ... people were always commenting on the billboard and asking for pictures for their daughters."
4 of 11
She may have a weakness for junk food, as the 29-year-old actress told Self, "but I also absolutely love fruit and vegetables." So it's no wonder that four years after her breakout role in The O.C., Bilson – who can be seen this fall in the CW pilot Hart of Dixie – has maintained her enviable California girl beach body.
5 of 11
Though Stefani, 41, has said, "Yoga or Pilates – they don't work for me," clearly the rocker mom (to Kingston, 5, and Zuma, 2) is doing something right. Her strategy for looking half her age? Cardio intervals and weight training four times a week with trainer Mike Heatlie, and several small meals a day of "lean meats, sweet potatoes for carbs and lots of green vegetables."
6 of 11
While his wife Gwen Stefani gets major props for her rocking body, the 45-year-old singer looked equally impressive putting on his own trunk show while vacationing in the South of France in May. His secret? Tennis. "[Most] mornings, five or six days a week, I'm doing stuff," the father of two told Tennis.com of his dedication to the sport.
7 of 11
KIM KARDASHIAN & KRIS HUMPHRIES
"Probably the sexiest thing about him is his personality," the reality star has said about her new fiancé, NBA star Kris Humphries, 26. We're guessing his washboard abs don't hurt either. As for her own much talked-about body, Kardashian, 30, admits she's had to come to terms with "huge boobs and a butt." These days, she tells PEOPLE, "I love my curves."
8 of 11
"Hugging him is like hugging a piece of furniture," Ellen DeGeneres marveled of the Criminal Minds actor. "You're so rock hard solid." And at 41, the former underwear model, who put his enviable body on display in Miami Beach in May, certainly looks as impeccable as he feels.
9 of 11
10 of 11
Topping last year's Most Amazing Bodies list, Efron, 23, isn't one to slack off – even managing to outdo himself while preparing to play a marine in an upcoming movie. "Zac put on 18 lbs. for his role in The Lucky One," a source tells PEOPLE. "Since then, he's lost weight but he's keeping up a fitness routine."
11 of 11
"I like anything green and I love steak," Cox once told PEOPLE. And by the looks of it, the Cougar Town star, who turns 47 on June 15, can afford to tuck into what she calls her favorite New York meal thanks to the Tracy Anderson Method. "It kicks my ass and I love it," she has said of the combination of dance aerobics and toning workout. "I was turned onto it in July , and I've seen a big change in my body."
To see the complete list of PEOPLE's Most Amazing Bodies of 2011, pick up the issue on newsstands Friday!