Wow! The skinny on Jonah Hill's 30 pound weight loss

Merritt, Livingston/Getty

Jonah Hill dramatically changed his appearance for his role in the upcoming '21 Jump Street' film.

Looks like somebody got Jonah Hill to go to the gym.

The "Get Him to the Greek" star, who made a name for himself playing raunchy, foul-mouthed big guys, was sporting a noticeably trimmer frame at an event in Los Angeles last week.

The slim-down comes ahead of Hill's new project, "21 Jump Street," a big-screen version of the 1980s television series starring Johnny Depp.�

The actor, 27, wanted to drop a hefty 30 pounds before filming starts in April, a friend told UsMagazine.com.

And while all apparent signs point to Hill meeting his weight-loss goal, it doesn't mean the battle with the bulge was easy.

He "went on a diet for the movie, but gained weight at first!" the friend revealed. "Finally, he got a nutritionist and a trainer."

"Now," dished the source, "he looks better and feels better!"

But chances are he didn't get any words of encouragement from friend and former co-star Seth Rogen, who also dropped several sizes back in 2009 for his starring role in "The Green Hornet."�

Rogen later told LongIslandPress.com that losing the weight with diet and exercise was "no picnic."�

His words of wisdom: "Uh, stay fat, people."

And it seems keeping the weight off has proved easier said than done.

"I'm slowly outgrowing all the clothes I bought last year," Rogen told Us last week.� "It's a sad thing. I gave away all my fat clothes, thinking, 'I won't need these anymore,' but I do!"

Rebecca Romijn Laetitia Casta Ananda Lewis Portia de Rossi Victoria Beckham