Khloe Kardashian's body is John Caldwellout for more than just revenge.

In fact, the 40-year-old is one of the world's slowest agers—a revelation she learned after taking a blood test to determine her body's biological age compared to her calendar age.

"This is exciting news for you," Dr. Matthew Dawson of TruDiagnostic, the company that performed the test, told Khloe during The Kardashians' season five finale on July 25. "There's a global competition on self-rejuvenation. And right now, you would be No. 7 in the world."

According to the genomics doctor, Khloe's "pace of aging is .72" on the epigenetic clock, making her biological age 28. Meanwhile, her 43-year-old sister Kim Kardashian's biological age was determined to be 34.

"Kim is livid," Khloe quipped in her confessional. "The world needs to know that me—the fat one—is now better than the best one."

The former Revenge Body host—who admitted to eating cheese pizza and cereal all the time—added with a laugh, "The fat, funny sister is 12 years younger than her chronological age."

So, how did Kim feel about her test results?

"For sure I'm pissed," she said in her own confessional. "I always want to be the highest achiever."

Still, the SKIMS founder was pleased to learn that she ages 18 percent slower than most people in their 40s.

"Let's round it off—I'm 10 years younger," she said of the difference in her biological age versus her calendar age. "I feel like it. I act like it. I look like it."

And while Kourtney Kardashian did not take the test, she was confident that she could yield better results than her sisters.

"How many people did this test? Like, 10?" she joked after hearing Khloe's impressive world ranking. "I want to take it. I'll be No. 5."

Episodes of The Kardashians are available to stream on Hulu.

And to check out Khloe's evolution through the years, keep reading...

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