Stars' Hot Bodies: As Seen on Twitter, Instagram

Rihanna

The "We Found Love" singer thanked designer Matthew Zink on Instagram for making "what has to be my favorite bikini of all time," a tan string two-piece. Also in the Instagram pic, Rihanna showed off her massive ribcage tattoo that honors her late grandmother.

Anna Kendrick

"I'm bringin' sexy back," Pitch Perfect's Kendrick joked, referencing Justin Timberlake's 2006 hit single "SexyBack" when sharing this snapshot from a trip to Puerto Rico. "'No tans lines' doesn't have scandalous implications for me. I'm basically see-through."

Bar Refaeli

"I don't feel the need to be super-skinny, but being in shape is important," explains Refaeli, who practices martial arts-based Krav Maga. "My trainer taught me all kinds of kicks and they work everywhere -- your abs, your butt."

The Rock

Credit: Courtesy of Dwayne Johnson

"It wasn't easy. It's a lot of hard work," pro wrestler Dwayne Johnson told USA Today of bulking up to play a bodybuilder in Pain & Gain opposite Mark Wahlberg. The actor said his added muscle appeared much larger on the big screen than it really was. "Onscreen, that small amount of extra pounds translates to 50 pounds, making my character look like an 800-pound silverback gorilla just released from jail."

Emmy Rossum

Credit: Courtesy of Emmy Rossum

 To keep her bikini bod (seen here in a carefree snap posted to Twitter) in perfect shape, the Shameless actress tries to cook for herself as often as possible. "I like making some vegan dishes, although I'm not vegan. I like making scrambled tofu with spinach and rice pilaf in a curry sauce," the actress tells Us. "Lots of good flavors you can add without adding too many unhealthy fats."

Harry Styles

Credit: Courtesy of Danny Simpson

The tattoo-covered singer -- who went shirtless with band mates Niall Horan, Zayn Malik, Liam Payne and Louis Tomlinson in One Direction's "Kiss You" video -- posed for an Instagram pic with English footballer Danny Simpson. After Styles' visit to Newcastle United's training camp, Simpson posted the pic to Instagram with the caption "proper safe guy."

Heidi Klum

Credit: Courtesy of Heidi Klum

"Island speed," the America's Got Talent judge captioned this Twitter shot from a vacation getaway, which showed her lying on her stomach (and flashing sideboob), tanning topless in only black bikini bottoms.

Justin Bieber

Credit: Courtesy of Justin Bieber

How does Bieber maintain his sexy six-pack? "He's pretty good about his diet," his voice coach Jan Smith tells Us. "He eats healthy. He doesn't eat a lot of junk food."

Maria Menounos

Credit: Courtesy of Maria Menounos

"I like to jog and I try to focus on floor-based Pilates to strengthen and lengthen," the super-fit Extra cohost (showing her midriff in a Twitter snapshot) tells Us. "I'm not someone who carries any kind of serious routine. I try to keep a healthy attitude about it. I deal with whatever it is. The most I will do before a beach trip is run a few nights before."

Mariah Carey

Credit: Courtesy of Mariah Carey

Welcoming twins Moroccan and Monroe in April 2011, the American Idol judge dropped 30 pounds in just three months by following a Jenny (formerly Jenny Craig)-approved diet and exercise routine."I feel incredible," the "#Beautiful" singer (pictured here in a Twitter snap from April 2013) said when unveiling her stunning weight loss in Us Weekly. "I'm proud of how hard I worked to get my body back...I had to do this for me."

Miley Cyrus

Credit: Courtesy of Miley Cyrus

No stranger to posting selfies on social media, Cyrus flashed her abs in a Twitter picture, which featured her in a bra top and studded leather jacket. In a recent interview with Elle U.K., Cyrus claimed she doesn't want to oversell her sex appeal. "A star is someone who doesn't have to take her clothes off to be sexy because you naturally have star power," she told Elle. "Sex does sell, but you have to find a way that's not just showing your tits. I don't want to be a glorified model."

Nicki Minaj

Credit: Courtesy of Nicki Minaj

"I don't mind the fascination . . . People are sitting in the barbershop talking about my butt. It's conversational," Minaj (posing in sky high heels and a curve-hugging pink frock on Twitter) told MTV in 2011. "That's what people are gonna do. As long as they're talking about Nicki Minaj, I'm good."

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