A dozen doughnuts, please! Katherine Heigl has quite the sweet tooth these days thanks to her pregnancy.

In particular, the Doubt actress, 37, has been craving doughnuts. "[I'm] trying really hard to stop [eating junk food]," she told Entertainment Tonight on Tuesday, September 27. "Just eat one doughnut a week. Just have one and then stop thinking about it."

"If I'm not on set, I don't think about them that much. And I don't eat them because they're not around," she added. "But on set, crafty always has a plethora of doughnuts in really pretty pink boxes, and I can't stop thinking about them."

Heigl doesn't feel guilty for indulging a little, though. "It's lovely, actually, because I feel absolutely no responsibility for my behavior at all," she joked. "It's great."

The Grey's Anatomy alum announced in June that she and her husband, musician Josh Kelley, are expanding their family. The couple, who wed in 2007, adopted daughters Naleigh, 7, in 2009 and Adalaide, 4, in 2012.

Heigl is currently filming the upcoming TV drama Doubt as she prepares for baby No. 3. She joked to ET that memorizing scripts has been difficult because of her pregnancy brain, but suggested that her growing belly won't be written into the show.

"Today was really impressive," she said. "I had to come up to my desk, and I didn't know that they had strategically placed [a desk lamp]. They were like, 'Katie, would you mind taking a small step to your right?' And I looked down and this lamp was right there. That's clever."

Can't get enough of Us? Sign up now for the Us Weekly newsletter packed with the latest celeb news, hot pics and more!