Matthew McConaughey's taking his upcoming role in The Dallas Buyer's Club super seriously ... the actor has to drop 30 pounds for the upcoming role of real-life AIDS victim Ron Woodroof. The actor showed off his slender frame as he waiting for a cab Friday in NYC.

The movie tells of a heterosexual Texas electrician who was diagnosed with AIDS in 1986; doctors gave him just a few months to live but he refused to accept their prognosis. Instead, Woodroof started an underground alternative treatment operation through which he smuggled illegal medicine to as many AIDS patients as he could. He ended up living six more years and prolonged the lives of countless others.

Whew! Pretty heavy, but pretty awesome -- can't wait to see this film!

Meanwhile, Matthew, 42, has got a third baby on the way and while wife Camila Alves gains weight in her baby bump, MM's got to avert his eyes while she's eating. He told reporters of his weight loss plan: "I am drinking a lot of tea. It takes a while for your body to understand that it has to feed off of itself and that you’re not going to give it something else from the outside."

Rihanna is a true fashionista! One day she's wearing a necklace with a four-letter word, and the next she's wearing a classic-style piece.

While leaving her favorite dinner spot Giorgio Baldi in LA, RiRi rocked a leather ensemble and a stunning Victorian cameo brooch. So chic!

We love when Rihanna wears minimal makeup. Watch her leaving the hotspot in our video below.

Christina Aguilera's latest single "Your Body" has leaked onto the web, and whoa, Xtina is gettin' nasty!

The songstress, who posted the above photo from the song's music video set, is singing the following lyrics: "All I wanna do is f**k your body, tonight's your lucky night I know you want me."

The Voice mentor said the following to Rolling Stone about her upcoming music:

"I'm one that likes to collaborate. I love feeding off the creative energy, and it only makes me better. I'm on a continual path both personally and professionally. All-around, it's my goal to better myself as a person and an artist, and the show is one of those contributing factors and the guys are great friends at this point. It's fun collaborating with them at this point."

Aguilera, who has been dating Matt Rutler for over two years now, sings: "I came here tonight to get you out of my mind, I’m gonna take what I find. So open the box, don’t need no key I’m unlocked. And I won’t tell you to stop."

X-Rated Xtina ... loves it!

Katy Perry and John Mayer's brief affair is over, reports claim.

The couple started dating earlier this summer and have been spotted together at the Chateau Marmont, a private party and a couple of dinner outings.

Perry, 27, is fresh off her divorce from Russell Brand, while Mayer, 34, has been out of the spotlight fo ra bit, since dating his last high-profile girlfriend, Jennifer Aniston.

So who's next for Katy and who's John's next conquest? Click through to tell us who YOU think the next victims are ...

Lance Armstrong announced Thursday he's giving up his battle against the US Anti-Doping Agency and will no longer defend their accusations that he's guilty of illegal doping during his decorated career. The USADA announced, thereafter, that it will strip Armstrong, 40, of his seven Tour de France titles and ban him from cycling for linfe.

Armstrong said in a statement on his website:

"There comes a point in every man's life when he has to say, 'Enough is enough.' For me, that time is now. I have been dealing with claims that I cheated and had an unfair advantage in winning my seven Tours since 1999. Over the past three years, I have been subjected to a two-year federal criminal investigation followed by [an] unconstitutional witch hunt. The toll this has taken on my family, and my work for our foundation and on me leads me to where I am today – finished with this nonsense."

USADA CEO Travis T. Tygart said: "This is a heartbreaking example of how the win-at-all costs culture of sport, if left unchecked, will overtake fair, safe and honest competition, but for clean athletes, it is a reassuring reminder that there is hope for future generations to compete on a level playing field without the use of performance-enhancing drugs."

Armstrong has twice retired from the sport -- first in 2005 and again in 2011. He battled testicular cancer in 1996 at age 25 and beat if with surgery and new chemotherapy treatments.

Armstrong wrote on his LiveStrong site:

"Today I turn the page. I will no longer address this issue, regardless of the circumstances," Armstrong said. "I will commit myself to the work I began before ever winning a single Tour de France title: serving people and families affected by cancer, especially those in underserved communities."

Snow White and the Huntsman director Rupert Sanders paid a visit to his estranged wife Liberty Ross Thursday -- it's one of a handful of visits he's made since photos of him in an illicit love affair with Kristen Stewart were splashed on magazine covers worldwide just weeks ago. Ross was in the pool with Sanders arrived. And note: he's still wearing his ring ...

For her part, Ross hit the red carpet Wednesday night for the Lawless premiere after-party. She was there to support her screenwriter pal Nick Cave.

Ross also returned to the blogosphere, posting a photo of a condor on her Vogue UK blog, which drew much speculation of its meaning. She titled the post, "Liberty," with comments leaving words of encouragement such as: "Free as a bird? Good luck to you Liberty,” and “lib, are you ok? Be strong for your kids."

Kim Kardashian acts her heart out in the upcoming Lifetime show Drop Dead Diva, set to air this Sunday at 9/8c.

You think Kim has a chance to make it in the acting world? ... If you don't already consider her "reality" show an acting effort!

Spider-Man co-stars and off-screen loves Emma Stone and Andrew Garfield showed some PDA in Malibu this week, with a hot and heavy make-out session on the beach!

Their stay-cation started Monday, when the pair hit the mall to pick up a sexy swimsuit for Emma. Tuesday we spotted the pair out celebrating Andrew's 29th birthday, with dinner at sushi hotspot Nobu.

Earlier on Tuesday, though, the sexy couple embraced on the beach, during the afternoon hours, while friends and a few other beach-goers looked on. "They were so cute - they look like best friends who are obsessed with each other. It was really sweet when they kissed," our source on the scene tells us.

Both Emma and Andrew caught some waves on a boogie board and played some beach volleyball with friends.

And as the crew headed home after a long, sandy day, Emma donned a t-shirt with her birthday message for Andrew ...