Everyone's favorite girl on Girls has been making quite a splash on the celebrity scene, and on the brink of the show's third season, Allison Williams has never looked better. The daughter of NBC Nightly News anchor Brian Williams surely owes her natural beauty to her genes, but that glowing skin and serious six-pack in the

Girls Season 3 promo don't come without hard work. We sat down with the star to learn more about the new season and how she stays in shape.

SHAPE: There's so much focus on weight gain and loss when it comes to you and your Girls castmates. Why do you think that is?

Allison Williams (AW): I think weight fluctuation is part of this decade that we're portraying on the show. So in a way, us just living our lives as twenty-somethings is mirroring what's happening in the show. It's not anything any of us are vigilant about or particularly preoccupied with. It's a healthy and sane set with regards to that it's not a part of the conversation.

SHAPE: How do you avoid nibbling all day when there are always snacks on the set?

AW: It's harder at the beginning of the season. Until you get kind of desensitized to it, the fact that there is a table of donuts sitting there for eight hours is like a test of something. Once you break the seal, if you have one donut hole, then you have six, and then eight, and then it's just over! So you have to be mindful of it because of the sugar rushes. You don't want to keep giving yourself a sugar spike and then crash and get exhausted and need coffee because you shoot for a long time. On set I eat a lot of peanut butter and apples, things that have actual energy and protein in them to keep me going.

SHAPE: What is your diet like regularly?

AW: I'm not a dieter. I have the palate of a 7-year-old boy, although I'm working on it. I order of the kids' menu! I'm working hard to eat more fruit and veggies and round it all out, but I'm a big pretzels and Diet Coke kind of girl.

SHAPE: What about your typical weekly fitness routine?

AW: I do two different things. For cardio I do SoulCycle. I really don't like to run, plus I have terrible knees and get bored on the elliptical. SoulCycle is basically a dance party on a bicycle, and you burn calories and it's so fun. Then I also do Core Fusion at Exhale Spa locations. It mixes together Pilates and barre method. It's really hard and kicks my butt, so those two together work perfectly. On a good week, I'd like to do two of each, but on a realistic week, it's one or two.

SHAPE: Tell us about your skincare routine.

AW: In order to have skin that glows and looks healthy and actually is healthy, you need to look at the whole picture and have a holistic approach to it. A lot of it is exercising regularly, drinking enough water, getting enough sleep, and keeping stress down. Otherwise, I use Simple Skincare cleansing wipes and protecting moisturizer, which has SPF and can go on under my makeup. And since I wear a lot of makeup when we're shooting, I use the foaming cleanser and eye makeup remover pads.

SHAPE: What's your go-to trick if you have a skin emergency?

AW: I'll just make sure I can set aside a day of no makeup and drinking a lot of water and relaxing. Maybe I'll put my face in a bowl of steam.

SHAPE: Has your dad ever given you on-screen skincare or makeup tips throughout the years?

AW: Oh my gosh, no! I would be mortified if he gave me makeup tips! I think we have a pretty different makeup routine, but it is funny that it's part of his job as well.

SHAPE: And what teases can you give us for next season of Girls?

AW: Well, Marnie is a little sad at the beginning of the season because Chris Abbot left the show, so we'll see her try to pick herself up after that. This season is one where the four girls are very proactively trying to start their lives. They're all deciding to become introspective and put in some effort. We get to see what happens when they really start trying.

Catch the Season 3 premiere of Girls on HBO on January 12 at 10 p.m. EST.