Adriana Lima: Dropping post-baby weight prior to Victoria's Secret show "biggest challenge of my life"

(CBS News) Some of the world's most beautiful women -- in the season's hottest lingerie -- will be on stage for Tuesday night's annual Victoria's Secret Fashion Show.

One of those women is supermodel Adriana Lima, who gave birth to a baby girl in September six weeks before the show was taped. Lima said shaping up for the show was "the biggest challenge of (her) life."

"You don't know what nature is going to return to you," Lima said on "CBS This Morning." "You do your job. I was working out. I was being a mom. ... I'm Brazilian and I'm a woman. I was really curvy when I was pregnant and I gained a lot of weight, really."

Asked what her definition of "a lot of weight is," Lima said, "Something over 40 pounds. Much, much, much more than that. I don't want to give it away. So it was a challenge. But nature was good, I guess. Thank you, nature."

Pictures: Victoria's Secret Fashion Show 2012: Backstage
Pictures: Victoria's Secret Fashion Show 2012 highlights
Pictures: Victoria's Secret Fashion Show 2012: Arrivals and after-party

Fellow Victoria's Secret "angel" Alessandra Ambrosio, who is also a mother of two, said being a model is, contrary to critics' views, a lot of work. "People think, 'You just have to look pretty.' It's not true. There's a lot of work that goes behind it and a lot of traveling and getting -- like looking good all the time, like being healthy."

Lima added, "Taking care of the kids behind that, newborns. Sleepless nights."

For more with the "angels" -- including talk about the $2.5 million bra, Justin Bieber performing on the show, and Ambrosio's childhood ear-pinning surgery -- watch the video in the player above.

The 2012 Victoria's Secret Fashion Show, airing Tuesday night at 10:00 p.m. Eastern / 9:00 p.m. Central on CBS.