Jonah Hill regains weight… on purpose?

He was plump. He lost weight. And now, he has gained it back.

Do Jonah Hill fans care either way? Similar to devotees of Oprah Winfrey -- whose weight has famously fluctuated over the years -- they sure don't seem to.

After losing more than 30 pounds before filming "21 Jump Street" last year, the Oscar nominated actor, now 28, seems to have gained it all back. It's possible, however, that he has done so purposefully for a character -- or two.

[Related: Jonah Hill on OMG!]

Hill's initial weight loss took place after filming "Moneyball" with Brad Pitt -- for which he was nominated for a best supporting actor Oscar. He is thought to have dropped weight for "21 Jump Street," co-starring Channing Tatum, to be in shape for the action sequences in the updated, comedic film version of the late '80s television show -- which starred Johnny Depp.

His decision to trim down in his words [via Metro, Sept. 2011]:

I went to a nutritionist. I wanted to be healthier. It's really as simple as that.

[Related: John Cusack, Anne Hathaway, and the Legacy of Robert De Niro's Weight Gain for 'Raging Bull']

Hill also told NY Mag that losing weight is a sign of "maturity":

...when I was 21 or 22 years old, with "Superbad"... I was a kid — I was drinking beer, smoking weed all the time. ... being healthier came along with maturity. And it's hard, because a lot of times people want you to be the guy you were when they met you. And I love doing funny movies, but I want to mature, literally, in how I treat myself. ... I just want to be a good man and to make my family proud. And, you know, I want to live a long time.

So what happened?

We do know he is in "The End of the World" with his buddies Seth Rogen and Jason Segel -- both of whom have also opened up about dropping weight. A slew of other stars are in the movie, which is currently filming, including James Franco, Rihanna, Emma Watson and Aziz Ansari. In it, everyone plays themselves -- at party at Franco's house during the impending Apocalypse. Could Hill have been tasked with looking extra Hill-y for the part?

[Related: Jessica Simpson's weight loss plan?]

Hill is seriously in demand as he has about seven yet-to-be released film projects he is attached to including the Martin Scorsese-directed "The Wolf of Wall Street," also starring Leonardo DiCaprio. In that film, due in theaters next year, Hill plays a man who gets caught in a life of greed and excess. (Could that include excessive eating?)

Stars most famous for their on-purpose fluctuating weight include Renee Zellweger (who put on about 20 pounds for her role as Bridget Jones) and Christian Bale (who dropped significant weight for both "The Fighter" (2010) and "The Machinist" (2004).

Methinks Hill -- or his publicist -- will comment soon on his gain-back.

Hill stars in the comedy "The Watch" with Ben Stiller and Vince Vaughn, in theaters July 27.

Watch recent Jonah Hill film scenes:

Clip from 'The Sitter' Clip from 'Moneyball' Clip from '21 Jump Street'