Kate Bosworth and her fiance Michael Polish in Beverly Hills, CA on December 17, 2012. Credit: London Entertainment/Splash

Kate Bosworth is going to be one very skinny bride.

The naturally slim 29-year-old looked tinier than ever when she stepped out with fiance Michael Polish on Monday, Dec. 17. Wearing a loose-fitting blouse and dark-colored jeans that hugged her long, lean legs, the Straw Dogs actress enjoyed a casual lunch in Beverly Hills with her director beau of more than a year.

The happy couple were all smiles as they strolled hand-in-hand to their car. However, Bosworth has said in the past that she tends to slim down in difficult times.

"Whenever anything happens that's very painful or stressful, we all lose weight -- my mother, my aunt, my grandmother," she told Vogue.

In any case, things seem to be going well for the pair, who met on the set of Big Sur (out later this year) and first stepped out together at a Coldplay concert in August 2011. In September 2012, Bosworth unveiled a square-cut diamond engagement ring from her husband-to-be via her WhoSay page.

"Thank you for all the wonderful engagement wishes," she wrote. "We feel truly blessed."