One of the most grueling part about being an actor is looking the part right. And sometimes, that involves some body changes and diet. From either dropping pounds or gaining them, these actors take their dedication to the role to the next-level. Check it out below:

Tom Hardy

Packed on 30 pounds to play Bane.

Bradley Cooper

Gained 40 pounds to bulk up for American Sniper.

Natalie Portman

Dropped 20 pounds to play the ballerina in "Black Swan."

Mila Kunis

Dropped 20 pounds for her role in Black Swan.

Hillary Swank

Gained 19 pounds of muscle for "Million Dollar Baby."

Ryan Gosling

Gained 60 pounds for "The Lovely Bones" but was fired for being 60 pounds heavier than he was supposed to be.

Demi Moore

Worked out with an ex-seal personal trainer for G.I. Jane.

George Clooney

Gained 30 pounds for his role in Syriana.

Charlize Theron

Gained 30 pounds for "Monster" and then dropped it right after.

Renee Zellweger

Gained and lost 20 pounds for Bridget Jones' Diary, Chicago and Bridget Jones: The Edge of Reason.

Vincent D'Onofrio

Gained 70 pounds for his role in "Full Metal Jacket."

Ben Kingsley

Shaved head and lost 20 pounds to play Gandhi.

Chris Pratt

Lost 60 pounds for Guardians of the Galaxy.

Anne Hathaway

Lost 16 pounds for "Les Miserables" and shaved her head for the role.

Jake Gyllenhaal

Lost 30 pounds for his role in "Nightcrawler."

Matt Damon

Put on 30 pounds for "The Informant."

Ryan Reynolds

Put on 25 pounds for "Blade Trinity" and kept it on for "Green Lantern."

Tom Hanks

Went from 225 pounds to 170 for "Castaway."

Christian Bale

Dropped 63 pounds for "The Machinist."



And then gained 44 pounds for "American Hustle."