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Kristin Cavallari has her body before baby look back ... and maybe more!

The former star of "The Hills" has flat out looked stunning lately, a mere five months after giving birth to her second child, Jaxon Wyatt. And, besides personal drive, she has Pilates to thank for it.

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"She might actually be tinier [than her pre-baby weight]," her Pilates instructor, Angeline Mitchell, told People. "She looks amazing!"

In getting her body back, Kristin attends two 55-minute private Pilates classes with her instructor. The focus, Angeline tells the magazine, is "relieving tight mommy hip," as well as the abdominal muscles and the shoulders. The classes, however, focus on a variety of stretching and body motion. The former reality-TV star also compliments her Pilates with strength training once a week.

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"The reason why she wanted to actually start doing Pilates was because she had heard that she could continue to do it throughout her pregnancy, and then also to get her body back after she has a baby," explains Angeline, who has worked with Kristin for the past year and a half.

Kristin's dedication is so strong, in fact, that she was back into her "pre-baby" jeans a month after Jaxon was born.

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"She's very conscious about she what she puts in her body, and she's super committed [to her workouts]," her instructor said. "She doesn't cancel and she likes to work hard, so she puts the time and the effort in. She's very consistent and she's very motivated and driven."

And Angeline's advice for other moms out there trying to lose the baby weight: "It's a process," she says. "You have to put in the time and the effort."