Renee Zellwegger looks like the perfect weight at the premiere of Mrs. Potter in London this weekend. It’s wrong of me to say that, because it just perpetuates the evil cycle that these Hollywood women go through to look good, but she’s not super skinny any more and looks really healthy. Would it kill her to use some gloss on those lips though?

Zellwegger said that not having time to eat while she’s working on the movie set helps her stay thin. She also claims that she’s a little bit intimidated at the thought of working with her once-rumored lover George Clooney because he’s a notorious prankster. They will start shooting the movie “Leatherheads” together in January.

Renee Zellweger, who showed up looking svelte at Sunday night’s London premiere of her new movie, Miss Potter, credits her slim figure to her work.

She says that the 20-minute lunch breaks she was allotted while making another movie, Case 39, helped her stay fit.

“That’s all we got on the set,” the Cold Mountain Oscar winner tells PEOPLE. “At that point, I was like, you know, forget it. And running around … everywhere, that helps.”

Zellweger, 37, joked that she finds out what diet she’s on by reading media reports. “I’m like, oh, oh, I’m doing that diet now – that’s fantastic! Good for me!”

As Peter Rabbit author Beatrix Potter, Zellweger is playing an English woman for the third time, having portrayed Bridget Jones twice. It’s having an effect, too: “I understand (and) crave the beans and toast breakfast,” she says.

But when it comes to living in the high-priced British capital, “I don’t know if I can afford it,” she told reporters. “I move around so much with work that I don’t really live anywhere.”

Next up for the actress: Leatherheads, with George Clooney. Shooting starts in January.

And how does she feel about working with PEOPLE’s Sexiest Man Alive? “I’m scared,” she admits. “I hear he’s a terrible prankster and really had patience… Like when you least expect it.”

As a result, “I’m going to be on alert, I’m never going to sleep, I’m sure of it. I’ll be watching my back, George!”

Considering that Clooney probably banged her a few times, it seems like she made a Freudian slip when she said she’ll be watching her, uh, back. Clooney is said to enjoy… entering establishments by the back door.

Renee is shown with Ewan McGregor, her costar in the film “Miss. Potter” at the premiere. (You know that people are still going to comment and say “that’s not George Clooney, duh.”) Here’s the trailer. Thanks to Faded Youth for these pictures.