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I should have known Christina Applegate would have a cozy living room. It's a "take your shoes off" kind of place in Los Angeles, and Christina, 40, is barefoot on her couch. She's wearing cargo pants and a sweater wrap, with a gold "Sadie" necklace. As for her 14-month-old daughter, Sadie? She's napping upstairs, but Christina is on high alert for the baby monitor.

"I love wake-ups," she says, smiling.

It's a rare break for the star of Up All Night, who likes to spend her downtime with Sadie and fiancé Martyn LeNoble. With her dog huddled at her feet, Christina talks about what she thinks now of the breast cancer she battled four years ago and the hopeful future she sees for herself and other women, too.

Is it true that Up All Night pulls from your own life as a mom?
Silly things. The birth episode had a lot of things that happened during my birth, having to have a headband and having my competition with myself pushing.

What are your favorite ways to stay fit?
Um, I'm not fit anymore—I had a baby! I haven't been working out because of the show. But when I was, I loved running. I'm looking forward to the show filming to be over so that I can get back to my schedule, which was five days a week, working my butt off. I miss moving my body.

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How do you eat healthy? Do you have go-to snacks?
I don't really snack so much. I meal it. I know there's the whole "You should eat five times a day," but I say eat when you're hungry. Because [that's when] your body's asking you to eat. I've been trying to keep a macrobiotic diet, but I do go off it when I feel like it during the week. Sometimes it's nice to have something that is enjoyable!

When did you start with the macrobiotic diet?
That all started when I found out I had cancer in 2008. I always ate really well anyway, so it wasn't an incredible change in my diet. But there's a certain way in which it's prepared and a certain way that you're eating that's geared toward healing.

After your breast cancer diagnosis when you were 36, you had a double mastectomy. Does that affect how you live today?
It's a scary thing that happened, and there is a lot of fear surrounding it still. Even though I'm four years out, it intensifies when you have a child. Your own health is really important. So I'm probably more—unfortunately, at this point—paranoid than I'd ever been before about when I go get my checkups and everything. I'm just scared. And I don't want to be. But that does add that kind of cloud when you have a baby. You want to make sure you're OK.

You founded Right Action for Women [which spreads awareness and helps fund breast cancer screening for women whose insurance doesn't cover it]. That must be so gratifying.
It feels wonderful. We just got some testimonials back today that I can't wait to put on the website [rightactionforwomen.org]. It's really, really wonderful for women who, because we were able to pay for their MRIs, found out that they had cancer early and are going to be OK. That is why I wanted to start the organization. And to bring awareness to the fact that it's not a woman-over-40s disease—not in the least.

Does it get any easier talking about it the more you do?
Sometimes it'll bring back memories. But listening to them, how scared they are, that always touches that chord again. Especially when one of the women said her doctor had told her she didn't need to get tests because she was under 40, and in that time, her cancer had spread so much. That kind of thing pisses me off about the medical community, that they're still spewing lies about who's getting this disease. So hopefully the foundation can develop more from just paying for MRIs to helping with treatments.

Do you think you will have another baby?
I would love to have one more. I know I'm 40, and people are gonna say, "Hmm..." I'll probably have to harvest in the next year [laughs] to make sure we have a backup plan.

To check out more of Christina's interview, visit health.com.