Actor body transformations have become a modern Hollywood tradition, though few examples exist prior to Robert De Niro’s iconic portrayal of boxer Jake LaMotta in 1980’s “Raging Bull.”

For the role, De Niro not only increased his strength and skills, but gained significant weight to depict LaMotta’s later physical decline – one of cinema’s most famous transformations.

Since then, numerous actors have followed suit, pushing physical limitations to fully inhabit important roles. The intense commitment likely imparts a mental effect as well, helping the performer walk in their character’s shoes. Though sometimes the accompanying film disappoints, the actor’s total commitment does not. (On a related note, here are the hardest-working actors in Hollywood)

To compile notable transformations, various sources like IMDb were consulted for instances of actors losing or gaining substantial weight or muscle for a specific part. The movie or TV show each actor participated in had a major body transformation come from IMDb.

Click here to see actors who made major body transformations for roles