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Kim Kardashian West is kicking her baby weight to the curb in rapid fashion.

The reality star showed off her post-baby weight after Justin Bieber's concert in Los Angles on Wednesday, stepping out in a body-hugging black skirt, matching sheer top and black bra. Earlier this week, Kim revealed that she's getting close to her target weight following the December birth of son, Saint West.

"Getting back in shape after I had North was SO tough," she said on her subscribers-only blog and app, referring to her two-year-old daughter. "I'm in the middle of doing the same thing right now after having Saint, and I'm so excited that I'm 42 lbs. down!"

Kim has said that her ultimate goal is to drop 70 pounds.

"Wearing my old workout clothes! They fit again," Kim proudly shared, adding that she wanted "more things to start fitting."

Kim has been trying to scrap the extra pounds she put on while pregnant with Saint, plus a few more she's been carrying around since the birth of her daughter.

"I gained 60lbs during my pregnancy but have been an extra 10 lbs up for the last few years so it's time to really get to my goal," she wrote on social media back in January. "This is going to be soooo f------ hard but I can do it and I can't wait to share it all with you!#BeastMode #WhosWithMe ?!?!?!"

She's reporting losing her weight by adhering to the Atkins 40 diet, which is high in protein but also allows more carbs than normal since she was still breastfeeding. She used Atkins following North's birth, too.

Whatever she doing, it's working.

Kim was joined at The Biebs' after party by her husband Kanye West and sister Kourtney Kardashian, who was once rumored to be hooking up with Justin.

The group, along with Kendall Jenner, Kylie Jenner and Tyga, all looked to be in good spirits earlier in the evening at the Staples Center concert. Kim posted a Snapchat with all of them in the frame with the word "Squad" written along the side.

Throughout the concert, the famous reality TV family stayed busy posted multiple videos to Snapchat.