Credit: Jim Spellman/

Natalie Portman lost an astonishing 20 lbs while training for her role in Black Swan -- but the vegan star is happy to gain it all back (and more!) now that she's eating for two.

"I told [director] Darren Aronofsky, I was like, 'First you got me skinny, and now you're getting my fat,' because he introduced me to my fiance," the pregnant actress, 29, told Extra at the Palm Springs International Film Festival Saturday. "It's the greatest gift he ever gave me."

A source tells Us Weekly that it was "seductive to watch" the 5'3" Harvard grad fall in love with French choreographer Benjamin Millepied when they met on the set of Black Swan. "There was no way the attraction could be missed. I don't think he could help himself -- she's dazzling!" the insider adds.

But don't expect to see much of the happy couple once awards season is over -- Portman says she's already made plans to take some time off to enjoy her pregnancy.

"I'm just doing these events, and then I'm going to try to take it easy," she told reporters over the weekend.