The 'Dawson's Creek' actress was taught from a young age that natural beauty and light make-up is best, and now tries to incorporate her mother's minimalist ethos into her work with Bobbi Brown cosmetics.
She told French ELLE magazine: "My mother, Kathleen, is a decorator. She's always told me that looking natural is the most beautiful. Make-up should make us refine our beauty. The creative side of the job is really fun and I discovered that the responsibilities that go hand-in-hand with it could also be fascinating."
Katie, who has just been replaced by Kate Upton as Bobbi Brown's celebrity spokesmodel, is constantly papped on the street in low-key looks and claims she doesn't care about what people think of her.
She said: "Even though I'm in an industry where what people think of you has a huge importance, I've stopped worrying about it. The only thing that matters to me is feeling good. And living life with serenity."
Katie previously confessed that her seven-year-old daughter Suri, who she has with her ex-husband Tom Cruise, is already showing an interest in make-up and says she has been trying to pass on her 'less is more' mantra to her own offspring.
The 35-year-old star explained: "My daughter Suri loves make-up. Usually I can't find my make-up when her friends come over. I tell her to be subtle with it. You can always put more on. Start with one product. You wouldn't wear all your jewellery at once."