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It seems like every day there's a new celebrity announcing her pregnancy—then hitting the runway or the red carpet in a barely-there outfit weeks after giving birth. Hollywood moms have plenty of incentive to get back into shape: Jessica Simpson recently struck a $3 million deal with Weight Watchers to use the program to lose her baby weight, while Bollywood actress Aishwarya Rai was criticized for not losing her pregnancy pounds quickly enough. (Her daughter was born in November, 2011.)

"Celebrities work hard and they put the time in, because their career depends on it," said Lisa DeFazio, a nutritionist in Los Angeles. While some stars may resort to surgery or dangerous cleanses, most simply diet and exercise—but have the money to afford personal trainers mail-order meals to speed the process. Here's 13 who bounced back in record time.

Beyoncé

Gracing the cover of People's Most Beautiful People issue in April 2012—four months after the birth of her first child, Blue—Beyonce told the magazine that she was back to her pre-pregnancy weight and felt "more beautiful than ever." In fact, she flaunted her famous curves just weeks after giving birth when she wore a figure-hugging dress to husband Jay-Z's Carnegie Hall concert in February. "I lost most of my weight from breastfeeding and I encourage women to do it; it's just so good for the baby and good for yourself," Knowles told People.

Bethenny Frankel

The Bethenny Ever After Star caused a stir in June, 2010 when she posed for Us Weekly in a size-4 swimsuit just three weeks after giving birth to daughter Bryn. Frankel responded with a statement to the website Momlogic, where she attributed Bryn's early arrival (five weeks premature)—as well as healthy eating habits and yoga throughout her pregnancy—to her ability to slim down so quickly. Later that year, she told Health she probably still weighed four or five more pounds than she did before pregnancy, but that she was "not even concerned about it."

Pink

"As soon as Pink had the green light from her doctor, we got to work," said Jeanette Jenkins, celebrity trainer and creator of The Hollywood Trainer DVD series, who's also helped Tia Mowrey and Alicia Keyes get their pre-baby bodies back. After the June 2011 birth of her daughter, Pink trained five days a week with Jenkins and followed a healthy meal plan in preparation for her fall tour and her first movie role in the upcoming "Thanks for Sharing."

Gwyneth Paltrow

Losing the baby weight after the birth of her second child in 2006 was "by far the hardest thing I have ever done," Paltrow said in 2010. She worked out two hours a day with the help of celebrity trainer Tracy Anderson, the Huffington Post reported, but also said that time constraints shouldn't be an excuse for any woman not to get her body back. "Every woman can make time—every woman—and you can do it with your baby in the room," she said. "There have been countless times where I've worked out with my kids crawling all over the place."

Miranda Kerr

The Australian model wasted no time getting back on the runway after the birth of her first son in January, 2012: Just two months later she made her post-pregnancy debut at Paris's Fashion Week. One month after that, she showed off her flat-again tummy during a bikini photo shoot in April. Kerr estimated that she gained between 30 and 40 pounds during her pregnancy, Fashionista.com reported in May, and said that yoga, breastfeeding and healthy eating (lots of veggies, fish, and lentils) helped her lose it so quickly. What's perhaps most impressive is that baby Flynn, her son with husband Orlando Bloom, weighed in at almost 10 pounds!

Mariah Carey

After the birth of her twins, Carey signed on as a spokesperson for the Jenny diet program (formerly Jenny Craig) and lost 70 pounds over the next six months—40 pounds of which, she says, was water weight caused by edema, or water retention, during her pregnancy. Because she had to recover from a Cesarean section, Carey couldn't exercise much at first, she said in the May 2012 issue of Shape magazine. "I realize that 90 percent of losing weight is my diet. "Assuming some of that weight was indeed due to water retention, Carey's stunning loss is not only healthy; it's actually doable, said DeFazio. "Two pounds a week, 10 pounds a month is safe, and you can do that without starving yourself or working out for hours every day."

Victoria Beckham

The former Spice Girl and fashion designer welcomed daughter Harper in July 2011 with husband David Beckham. The Daily Mail reported that the mom of four was following the Five Hands Diet—which involves eating only five handfuls of food a day—so she could slim down in time for New York's Fashion Week in September. Months later, however, Beckham told Vogue magazine that she lost her pregnancy weight by running six days a week and following a workout created by her trainer, Tracy Anderson.

In 1999, photos of a skinnier-than-ever Beckham, taken just months after the birth of her first child, Brooklyn, sparked controversy and earned her the nickname "Skeletal Spice."Beckham has said that she ate normally, and couldn't help losing so much weight.
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Jessica Alba

Although the actress has said that her body will never truly be the same again after having kids, her rockin' bikini abs told a different story just four months after giving birth to daughter No. 2 when she was photographed on vacation in December, 2011. Alba told reporters that chasing a 3-year-old around the house and working out with a trainer (doing full-body exercises like Burpees) has helped her lose weight fast.

She's got the right idea, said Jenkins. "Core work is really important, because you have to rebuild all of the muscle memory in that area."A good fitness routine for new moms, she says, concentrates on increasing muscular strength, improving flexibility, and building back cardiovascular endurance.

Kelly Preston

The actress lost lost 42 pounds and got back to her high-school jeans size 14 months after the birth of her son in November, 2010 with husband John Travolta. Preston, who craved powdered donuts and cinnamon muffins while pregnant, says she worried about her weight when she left the hospital after giving birth. "I looked just as pregnant as when I went in," she told People in February, 2012. "I didn't know what my body was going to do—if it would bounce back or if I was going to be 20 pounds heavier for the rest of my life."

Preston took a year off from acting and began exercising and using Organic Liaison, a weight-loss supplement program created by Kirstie Alley.

Niki Taylor

The supermodel and former Celebrity Apprentice contestant gave birth to her third child in 2009. Over the next 13 months, she lost 59 pounds by eating healthfully—oatmeal sprinkled with berries and chicken broiled in coconut oil were two of her post-pregnancy staples—and exercising at least 30 minutes a day. "If I have dessert, I spend half an hour more exercising," Taylor told People in May, 2010.

Jennifer Garner

After the birth of her second daughter, Garner took her time getting back into pre-baby shape, her long-time trainer told People in October, 2009; she started exercising again three weeks after baby Serafina arrived, but took her time and spent nine months getting back to her pre-baby body. When Garner's first son was born in February, 2012, however, she seemed more anxious to get back in shape and into the spotlight. Just two months after Samuel's birth, Garner wowed the media at her first postpartum red-carpet appearance, at CinemaCon in Las Vegas.

Milla Jovovich

While pregnant in 2007, Jovovich was known to eat three peanut-butter-and-jelly bagel sandwiches a day, and her weight reached 192 pounds. To slim down post-baby in time for her next film—which included bikini scenes!—the actress recruited celebrity trainer Harley Pasternak to work out with her five days a week. Jovovich also followed Pasternak's 5 Factor Diet, which emphasize three small meals and two snacks a day. In just five months, she lost 62 pounds, and used circuit training to get her toned figure back.

Alessandra Ambrosio

"Tiny portions," "brown rice instead of white," and "lots of salads" helped this Victoria's Secret model drop 45 pounds in just three months after giving birth, she told People in December, 2008. To prepare for the brand's famous fashion show in November, Ambrosio also exercised for two to three hours a day while her mother or sister watched her daughter.

What's normal?

Losing weight after you've had a baby is not the same as dieting just because you're overweight: New moms are sleep deprived, crunched for time, and caring not just for themselves, but for an infant, as well. "Your body goes through a lot, so you shouldn't start any crazy dieting or restricting calories for at least six weeks," said DeFazio. Moms who are breastfeeding need around 1800 calories a day, she adds (otherwise your body will start producing toxins that can get into your breast milk), while most commercial diet plans limit you to between 1000 and 1500.

What should "normal" moms do?

New moms should also wait about six weeks before diving into any strenuous exercise, said Jenkins—or longer if you've had a Cesarean section. Eating well and staying active during your pregnancy can make it easier to get back in shape afterward, she adds. "You can't compare yourself to any other woman, because every woman is starting from a different level. Every new mom can get back to her pre-baby body, but the best way to do that is to figure out how to make it work for your own life and to listen to your own body."