Actors and actresses are pretty amazing beings. For each and every role, which may be completely different from the next, they literally transform themselves into a totally different character. Sometimes, the actor goes so far as to change their bodies to fit the needs of the character they’re playing.

Whether it’s losing weight, gaining weight, or whatever else, here are 17 actors who went to the extreme to completely transform what they looked like for certain movie roles. You won’t believe what they looked like!

1. Chris Pratt in Guardians of the Galaxy

   60 pounds lost in just six months!

2. Jake Gyllenhaal in Southpaw

   He gained 15 pounds of muscle after working out for six hours a day for six months.

3. Jonah Hill in Maniac

   He looked almost unrecognizable to previous roles.

4. Natalie Portman in Black Swan

   She thought she was going to die after a 20-pound weight loss from a crash diet and eight-hour rehearsal days.

5. Christian Bale in American Hustle

   He gained 42 pounds and shaved his head, not to mention suffered a herniated disc when giving his character a real-life slouched posture.

6. Tom Hanks in Cast Away

   Since he plays two characters in the film, he had to first put on 50 pounds, and then take a year to lose it, plus grow out his hair (head and facial).

7. 50 Cent in All Things Fall Apart

   A nearly 60-pound weight loss for the role of a cancer patient football player.

8. Matthew McConaughey in Dallas Buyers Club

   He lost more than 40 pounds to convey AIDS patient Ron Woodroof.

9. Demi Moore in GI Jane

   She actually competed real Navy SEAL training, among other exercises, for the role. Can we say hardcore?

10. Charlize Theron in Monster

    A 30-pound gain to play a real-life serial killer.

11. Zac Efron in Baywatch

    Definitely no carbs or sugar for Zac, plus 4-5 workotus a week with fitness trainer Patrick Murphy.

12. Anne Hathaway in Les Miserables

    A special diet and a noteworthy haircut later for this role.

13. Ben Kingsley in Ghandi

    Not only did he shave his head and lose 20 pounds for the role, he also got into the character side of it by studying yoga, starting to meditate and learning to spin cotton thread on a wooden wheel.

14. Renee Zellweger in Bridget Jones: Edge Of Reason

    She gained 30 pounds, going from a size 4 to 14. It took a while for her to re-lose it!

15. Colin Farrell in The Lobster

    A 40-pound weight gain in just two months!

16. Rooney Mara in The Girl With The Dragon Tattoo

    She went to the extreme with dieting to portray a “pale, anorexic” character.

17. Matt Damon in The Informant!

    He gained around 30 pounds to be more “doughy.” His secret? Beers and burgers and just having a good old time.

Wow—these transformations are insane! Would you ever transform yourself like this for a cool movie role?