You might have the idea that acting is an easy job, and maybe sometimes it totally is (see Meryl Streep in Mamma Mia!). For the actors in the following roles, though, that certainly wasn’t the case. These actors made total transformations and proved some serious commitment to their craft.

#20. Jake Gyllenhaal in Southpaw

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He had to gain 45 pounds after Nightcrawler, most of it muscle.

“I went into full training-camp mode and I got myself—what I consider in my mind as an actor—in shape to fight. I was literally learning the skills of boxing, which is not only for the body, but also for the mind. You can’t play a boxer and just look like a boxer; you have to believe you can exist in that world.”

#19. 50 Cent in Things Fall Apart

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Telling his best friend’s story was worth the 54 pound loss.

“I had so much muscle on me that it was hard for me to lose definition even as I got lighter and slimmer. I started running to suppress my appetite. Towards 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.”

#18. Matthew McConaughey in Dallas Buyers Club

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He lost 47 pounds for his Oscar-nominated role.

“That was rough. I got down to 143 pounds and I was always hungry, and irritable. My body resembled a baby bird with its mouth open, crying, ‘Feed me, feed me,’ and you realize momma bird ain’t going to feed you. It’s hard.”

#17. Tom Hanks in Cast Away

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“The hardest thing was the time. I wish I could have just taken a pill and lost all the weight but the reality was that I had to start in October knowing that we were going to go back in February. The idea of looking at four months of constant vigilance as far as what I ate, as well as two hours a day in the gym doing nothing but a monotonous kind of work-out, that was formidable. You have to power yourself through it almost by some sort of meditation trickery. It’s not glamorous.”

Welcome to being a woman, Mr. Hanks. Congrats on the ability to drop 50 pounds.

#16. Robert De Niro in Raging Bull

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You might have forgotten in recent years that De Niro used to be a serious actor – like in Raging Bull, when he packed on 60 pounds.

“The first 15 pounds was fun, the rest was hard work.”

#15. Anne Hathaway in Les Misérables

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For her role as Fantine, Hathaway hired a nutritionist to help her lose 25 pounds-10 before filming started and another 15 (by basically starving herself) during the 13-day shoot.

#14. Matthew Fox in Alex Cross

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His thoughts on losing 44 pounds:

“If I’m honest, sometimes I f**king hated it. I guess if you removed the ‘result’ part of it then I can’t say I enjoyed it.”

#13. Matt Damon in The Informant

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I know these have their downsides, but it has to be more fun to gain than lose, right? Thanks for being honest, Matt Damon.

“It was very, very easy to gain the weight. It was very, very fun, probably the funnest time I had working, because I didn’t have to go to the gym after work and I just ate everything I could see.”