Last summer, Melissa Joan Hart took a bad picture.

A really bad picture.

Paparazzi caught her on a California beach looking more like Kirstie Alley than the "Sabrina, Teenage Witch" star people were used to seeing.

"I still read blogs about me discussing how fat I've become," she tells the new issue of People Magazine, which goes on sale Friday.

PHOTOS: Click for "before and after" pics of Melissa Joan Hart.

The 33-year-old decided it was time to whip her post-pregnancy body - she has two sons, ages 3 and 14 months - back into shape.

MORE: Go to People.com for more on Melissa's transformation.

With inspiration from friend and fellow Hollywood mom Jaime Pressly, Melissa got to work. "I realized I didn't have to be heavy just because I have kids," she says.

Fourteen months and 42 pounds later, the old Melissa is back. "It didn't happen by magic," she says. "It was as hard for me as it would be for anyone else."

"She finally took the time to take care of herself," Pressly tells People. "I'm blown away by how amazing she looks."

Hart is best known for her role in the hit teenage sitcoms "Sabrina" and "Clarissa Explains It All." She also starred in several hit teen movies including "You Drive Me Crazy" with Adrian Grenier and "Can't Hardly Wait," as well as the ABC Family original movies "Holiday in Handcuffs" and "My Fake Fiance." She is married to musician Mark Wilkerson, who is the frontman for the band Course of Nature.

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PHOTOS: Before and after pics of Verlie Bertinelli.