Here's the thing about Chyler Leigh: she looks wholesome and, well, pretty damn perfect. Kind of like Dr Lexie Grey, the prom queen turned Harvard med student she plays on Grey's Anatomy. But in real life she's been infinitely less predictable and a lot more, shall we say, nuanced. Leigh started modelling at age 12, and ended up experimenting with drugs.

She tried her luck with acting and had enough near misses with fame - including a lead role in Not Another Teen Movie and a few star turns on failed TV shows - to make her a jaded pro at an age when most girls haven't finished high school. Then, after turning 20, she kicked her collection of bad habits, married her longtime boyfriend - actor/muso Nathan West - and underwent the kind of internal makeover that keeps a celeb off the pages of gossip mags. And now? The 26-year-old actress is mum to son Noah, 5, and daughter Taelyn, 2, as well as being pregnant with her third child - and her career has never looked better

I've been a chameleon through my entire career. I can change my appearance by doing simple things. People ask, "What's your ethnicity? Are you part Asian? I can't figure you out." That gives me range with the roles I play.

I went through an experimental drug phase, being a silly teenager. When I was 19 I was doing drugs, drinking, barely eating. I'm five six and a half [172cm], and I got down to 103 pounds [47kg]. It was really scary.

I've always had problems with digestion, but when I was doing drugs I ended up getting really sick. I couldn't hold food in my body. You could see bones everywhere. I had to see a doctor to regulate my system.

The more I worked on the stuff inside, the more changes happened for me. Nathan and I thought, "We could keep going down this road - but it's not going to lead us anywhere good".

Now we eat very well in our house, with as much organic food as possible, as well as lots of vegetables and fruits. I've been doing a lot of research, trying to figure out what diet works best for all of us, and what will help us operate at our peak. Lately, we've been following the Blood Type Diet, and it's been incredible, energy-wise. According to this diet, type As [like Leigh and her son] have low stomach acid, so they should avoid meat. It's too bad, because I love a steak.

I have exercise-induced asthma, so I keep my energy levels up by chasing two small children around. I stay as active as possible without going to the gym.

I'd love to run more - just to get that good, clear thinking time. Nathan has these running epiphanies. He'll go out for a run and come back and say, "Look, I said this and I'm sorry," or "I totally figured this out". And I'm like, "Go again!"

Want to know more about Chyler? Check out the March issue of WH for the full article.