Beyonce flaunted her slim post-baby body on Monday night in New York City for a fundraiser held by Michelle Obama for the President's re-election campaign, wearing a snug blue dress that showcased her weight loss.

Her appearance with a slimmed down figure comes just 10 weeks after giving birth to her daughter, baby Blue Ivy Carter, attending the event with husband Jay-Z, 42, mom Tina Knowles and mother-in-law Gloria Carter.

Beyonce, 30, was wearing a dress by Victoria Beckham, according to Yahoo News to the fundraiser at New York's Greenwich Hotel, pairing it with a long necklace, strapped heels and electric blue nail polish.

But how did she lose the baby weight and get that flat tummy back so quickly?

According to Star magazine, trainer Marco Borges has been living in her home where she exercises twice a day at 5 a.m. and 5 p.m.

"Beyoncé and Marco are up at 5 a.m. for a two-hour workout, and they do it again at 5 p.m.," an unnamed source told Star. "They do a mix of cardio, Pilates, plyometrics, yoga and, of course, dance."

Beyonce has also complemented her strict workout regimen with a diet of "protein shakes, egg-white omelets, pineapple chunks, and lots of ice-cold water"

"Beyoncé and Marco are up at 5 a.m. for a two-hour workout, and they do it again at 5 p.m.," the source told Star. "They do a mix of cardio, Pilates, plyometrics, yoga and, of course, dance."

In addition to the weight loss, Beyonce announced on Tuesday that she will hold her first post-baby performance during Memorial Day weekend in Atlantic City with a trio of concerts from May 25 to May 27.

"Brand new resort + Memorial Day Weekend + summer kickoff party + new live show = Beyoncé getting back to business live on stage at Revel," the post on her website said. "Three exclusive shows with the unstoppable star at the brand new beachfront resort.'"

View the slideshow to see photos of Beyonce and her weight loss at the Obama funraiser.

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