Matthew McConaughey and More Stars' Extreme Weight Loss

Aug. 30, 2012 — -- intro: Matthew McConaughey appears to have melted.

The formerly buff actor struggled to fill out his suit on the set of "The Wolf of Wall Street" in New York this week. He's losing 30 pounds to play an AIDS patient turned drug dealer in the upcoming movie "The Dallas Buyer's Club," which starts shooting next month. He told Larry King he views not eating as a cleanse.

"It's a bit of a spiritual cleanse, mental cleanse," the 42-year-old actor said in an appearance on the veteran newsman's Ora TV online show. "[I'm] 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," McConaughey said. "I should not look healthy by the time I'm doing this."

Yikes. McConaughey's not the only actor to push the boundaries of health for a role. Click through to see six more who've gone to extreme and sometimes unhealthy measures to get into character:

quicklist: 1title: Anne Hathawaytext: There are diets, and then there are diets. Take, for example, Anne Hathaway: In preparation to fit into her Catwoman suit for "The Dark Knight Rises" and play the tuberculosis-ridden prostitute Fantine in the upcoming movie version of "Les Miserables," the 29-year-old actress subsisted on a 500-calorie diet of radishes and hummus.

"I'm on day six of detox," she told Allure magazine. "This diet makes me break out, so I love that. Nothing like living on hummus and radishes and then be all, 'And I got a pimple. Yeah!'"

On top of that, she worked out.

"The Catwoman suit. It was a psychological terrorist," she said. "The suit, thoughts of my suit, changing my life so I would fit into that suit. ... It dominated my year. I went into the gym for 10 months and didn't come out."media: 16606257

quicklist: 2title: 50 Centtext: When Curtis Jackson, better known as rapper 50 Cent, decided to make "Things Fall Apart," a movie about his childhood friend's cancer battle, he committed to getting as skinny as possible.

"I had so much muscle on me that it was hard for me to lose definition even as I got lighter and slimmer," he told Parade magazine. "I started running to suppress my appetite. Toward the end it was really difficult. It was like, if I don't get close enough to what my best friend looked like to me at that point before he passed, then I'm not doing the story any justice."

When the going got tough, he took to the Internet to read how actors like Christian Bale and Tom Hanks lost weight for their own projects.

"I actually got on the computer," he told the Associated Press. "When it started getting difficult, I was looking to see what their experience was like, and I got a chance to see all the interviews they had at different time periods when they were doing promotion for the projects."media: 17108433

quicklist: 3title: Natalie Portmantext: When Portman dropped more than a dozen pounds to play a ballerina in her Oscar-winning movie "Black Swan," even her director worried the petite actress had gone too far.

"At a certain point, I looked at [Natalie's] back, and she was so skinny and so cut," director Darren Aronofsky told "Access Hollywood." "I was like, 'Natalie, start eating.' I made sure she had a bunch of food in her trailer."

A year before shooting "Swan," Portman went through extreme ballet and cross-training, shedding 20 pounds from her 5-foot-3-inch frame.

"I think it was just the physicality of it all that was the most extreme," she told UsMagazine.com. "I mean, I had never gotten that much training -- to be doing five-to-eight hours a day ... was really a challenge."

As soon as filming wrapped, Portman, who'd danced as a kid, was happy to leave the ballet world behind. She told "Access Hollywood" that she immediately ceased working out and began carbo-loading to bulk up again.

"I was like, pasta, pasta, pasta! No working out," Portman said. "It was pretty immediate. I was ready to leave the ballet life.media: 16606173

quicklist: 4title: Mila Kunistext: Portman's "Swan" co-star Kunis also dropped 20 pounds to play a ballerina.

For three months, the "That '70s Show" alum trained, through ballet, cardio exercises and Pilates four-to-five hours a day, seven days a week.

In the end, she became frightened by her own reflection. "I could see why this industry is so f**ked up, because at 95 pounds, I would literally look at myself in the mirror, and I was like, 'Oh my God!'" the 5-foot-3-inch actress told E! Online. "I had no shape, no boobs, no ass. ... All you saw was bone. I was like, 'This looks gross.'" She told E! that it took her only five days to put the weight back on.media: 16606160

quicklist: 5title: Gwyneth Paltrowtext: Paltrow packed on 20 pounds to play an alcoholic singer in "Country Strong" but admitted she panicked at the thought of not being able to stick to her strict diet and workout regimen, which includes exercising two hours a day, six days a week, afterward.

"The nightmare thing about it is I had to stop working out," she told Chelsea Handler on "Chelsea Lately." "At first I panicked, so I would work out a little bit, and then I had to lie and be like, 'No I didn't work out.' I'd be on the treadmill and be like, 'I really have to stop this.'"

Her trainer, Tracy Anderson, also had a hard time watching Paltrow bulk up.

"That was tough for me because we've worked so hard on her body," Anderson told ABC News' New York station WABC. "She went down from six days a week of training to three, and she ate everything in sight. Fried chicken, mashed potatoes. They filmed in Nashville, so it's a good place to have some comfort food."

But even if few others seemed to notice a heavier Paltrow, the actress couldn't wait to shed the excess with Anderson's combination of dance, cardio and weight exercises.

"It didn't take her very long to lose the weight. It only took her a couple of weeks. It didn't want to be on her anyway. Extra weight isn't something that she owned," Anderson told WABC.

And it was just in time for her debut singing appearance at the Country Music Awards.media: 16606108

quicklist: 6title: Amanda Seyfriedtext: Seyfried credited the raw food diet for helping her get the slim physique she displayed in 2009's "Chloe."

"It's intense. And sort of awful," Seyfried told Esquire of the diet that forbids eating cooked or processed foods. "Yesterday for lunch? Spinach. Just spinach, spinach and some seeds."

But Seyfried was willing to suffer for her art.

"I have to stay in shape because I am an actress," Seyfried told Glamour magazine. "It's twisted, but I wouldn't get the roles otherwise."media: 16606052