The Oscar-winner, who had a son in May, says there's 'no magic potion' after childbirth

Rachel Weisz says there’s no big secret to getting back in shape after giving birth – but she does have a few suggestions.

“I don’t really have a magic potion or pill,” she told PEOPLE at a British Academy of Film and Television Arts event Thursday in Los Angeles. “I do Pilates. Nursing burns a lot of calories, 500 calories a day. So, if I could help promote breast-feeding, that would be a good way.”

Weisz, 35, gave birth to a son, Henry, on May 31. The father is Weisz’s fianc , feature-film director Darren Aronofsky, 37, who directed Weisz in the current movie The Fountain.

Weisz was at the BAFTA event to accept the Britannia Artist of the Year Award. Since appearing at the Oscars in March, she says she has taken some time off to focus on motherhood.

“I was seven months pregnant when I won the Academy Award!” she says. “Really, since then, I’ve just been a mom, mainly. It’s the most ultimate honor you can get. But I had to duck out of the rat race for a bit and be Mom.

Weisz, who is getting back to work by filming the Adam Brooks comedy Definitely, Maybe, says that has a newfound appreciation for women who juggle career and motherhood.

“I have respect for all working moms out there, because it’s definitely a complicated balancing act, which millions of women are doing all the time,” she said. “But I’m part of that club now.”