Renée Zellweger: You don't want to see what's going on under this turtleneck

Renée Zellweger, 33, was born in Houston and raised in rural Katy, Texas. Her first major role came in 1994 with The Return of the Texas Chainsaw Massacre. By 1996 she was playing opposite Tom Cruise in Jerry Maguire. Best known for her work in Bridget Jones's Diary, Zellweger now stars as Roxie Hart in the screen musical Chicago and is currently filming Cold Mountain with Anthony Minghella in Romania. Recent loves: Jim Carrey, George Clooney. Current flame: coffee (status: inseparable).

I see you're still addicted to Starbucks

Oh, isn't it pathetic? It's so sad, it's ridiculous. I even brought my own stash of beans to Romania for Cold Mountain. Every night I was grinding coffee. And every morning I was making it for everyone because, eventually, they all found out about it. I was, and remain, The Bean Queen.

So you stay in shape with a strict caffeine diet?

Well, I also did The Transylvania-Romania-Cold Mountain Workout. Basically it's running up and down a mountain all day, every day. Because Anthony [Minghella], God bless him, would want to see it again and again and again. I'd have a big potato sack on this arm – you should feel these biceps, I'm very proud of them right now – and a huge rifle here. We were mending fences, shovelling crap out of the barn, loading up the horse, unloading the horse. I'm telling you, yard work ain't what it used to be.

How did you train for Chicago?

We spent three months with [director] Rob Marshall, just singing and dancing on stage. It was kind of like school. "OK, Missy, you just get up there and do it!" And that was that. We didn't have time to step back and say, "How are we doing?" It continued like that until we were shooting. And even then he would step in and make changes, teaching us something new on the spot. It was an ongoing process until, well, just a few weeks ago.

Had you seen it on stage?

Never. I didn't know what the story was. I hadn't heard the songs. Nothing. I mean, I always feel like an imposter, but this time I really felt like one. I've never opened my mouth to sing in front of a bunch of people and I've certainly never danced a lick in heels, except for my prom. And I didn't care because I liked that guy. Rob was so smart and so brilliant that I was going to be a part of anything he was going to create. I didn't care if we had to do it at the Veterans' Hall down the street and my mom made the costumes and only my neighbours came to see it. I don't know why Rob thought this would be a good idea, but he did. And I'm glad he did.

You seem to go to extremes with your films

I like roles that offer an opportunity to develop a side of yourself that you haven't been called on to develop before, that make you grow in some way, that broaden your perspective in some way. Whatever you do, isn't that your goal ultimately?

And off-screen?

I don't need to go to the moon. I don't need to go to the bottom of the ocean. I'm very happy just sitting right here. Sad but true – I'm very boring.

Judging from your racy photo shoots for Chicago, I'd say anything but

Roxie Hart is a character who uses sexuality as currency. But me? Well, I'm not that self-aware. I don't guss myself up every day and ask, "What am I using today?" It's not interesting to me. I like to put on a pair of high heels every now and then because I like 'em. I'll wear a skirt when it feels appropriate or a gown if it's an opportunity to dress up. But not because I'm afraid of what people will say if I wear sweats.

You seem to be more confident now than ever. What happened?

I'm not a girl anymore. I'm growing up and I'm learning – about myself and my boundaries. Fame is a job which comes along with the job I love so much. No one is born with the faculties to deal with being a public figure. But I've learned that fame only exists from the outside. I get up in the morning; I clean the poop off the floor, and there's no fame. I walk the dog, feed the cat, and there's no fame. I call my mom and there's no fame. I take my shower, drive my car down the road, go to work, get blisters on my feet, and there is no fame. I just go from one thing to the next without thinking about things that are projected on to me.

It's been said that your vulnerability on screen has been your greatest asset. Are you truly that vulnerable?

That's one of those questions that would require me to walk around and ask myself how endearing I am... I would say that I care. There's nothing that's superficial in my life; I don't have time for it. Not my friends, not the choices that I make, not my work, not what I do with my day. Maybe that makes me sensitive – that I care about stuff too much.

Will you make a sequel to Bridget Jones's Diary?

Maybe. They're talking about doing it. But I cherish Bridget and all that came along with that experience from the moment I opened the book. So it's something I'd be very careful with. I don't want to do it just because there's a book there and we can. If it's special and if it needs to be made, I think that she has more stories to tell.

Would you put the weight on again?

That would be part of doing it right. That would be part of maintaining what's special about her, which is becoming her. Just like I'd go and get a dumb haircut for a role. Just like I have a rash all over my neck now from Romania. That's part of the job.

A rash and a haircut can be fixed up quickly, whereas with weight...

Actually, it depends on the rash. I've got a pretty nice, heavy duty Romanian one going on right now. Trust me – you don't want to see what's going on under this turtleneck.

'Chicago' opens nationwide on 17 Jan