The reality TV star, who walked the red carpet with Pete Davidson, said she had to lose 16 pounds to fit into the dress.
Kardashian first tried on a replica of the Bob Mackie dress — which sold at an auction for $4.8 million in 2016 and is now at Ripley's Believe It Or Not Museum in Orlando, Florida — and it fit perfectly, according to Vogue.
But when the original dress was flown to Kardashian's home in Los Angeles a few weeks ago, the fitting didn't go quite as planned.
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"The dress was transported by guards and I had to wear gloves to try it on," Kardashian told Vogue. "I always thought she was extremely curvy. I imagined I might be smaller in some places where she was bigger and bigger in places where she was smaller. So when it didn't fit me I wanted to cry because it can't be altered at all."
Instead of finding a new outfit for the Met Gala, Kardashian decided she would lose the weight.
"It was like a role, I was determined to fit it," she told La La Anthony during Vogue's red-carpet livestream at the Met Gala on Monday.
Kardashian completely cut out sugar and carbs from her diet, ran on the treadmill, and wore a sauna suit twice a day, she told Vogue magazine.
"I didn't starve myself, but I was so strict," she said. "Just the cleanest veggies and protein."
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Kardashian then went to the Orlando museum to try the dress on one more time, and said she wanted to "cry tears of joy" when it fit like a glove.
And that wasn't all Kardashian did to take her Met Gala look to the next level.
The SKIMS founder also revealed that she spent 14 hours getting her hair bleached blonde on Sunday to match Monroe's iconic locks.
Since the original Monroe dress is so fragile, Kardashian only wore it for a few minutes before switching into the replica on Monday night.
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After weeks of dieting to fit into what Kardashian calls "the original naked dress," the reality TV star said she has big plans to celebrate with pizza and doughnuts.
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