Khloe Kardashian Learns Her Biological Age Is Way Better Than Kim's

Khloe Kardashian's bad eating habits aren't coming back to haunt her ... as she learned an impressive fact about her overall health.

The Good American founder discovered her biological age after taking a test alongside mom Kris Jenner and sister Kim Kardashian on the season 5 finale of "The Kardashians." Khloe said she was seriously worried about her results, since she was an avid junk food junkie.

Yet, the test results showed Khloe -- who's now 40 -- has the biological age of a 28-year-old... which prompted her to jump for joy.

She was stunned ... "Never in a million years! If I had to bet money, I would’ve never bet on myself ... Kim is livid, by the way. I know she’s pissed."

As for Kim's response ... her envy was palpable ... especially since her biological age was 34.

Khloe shouldn't be all that shocked ... she does vigorous workouts on the regular -- confessing the "fat one" label still hurts her.

She added ... "The world needs to know that me, the fat one, is now better than the best one ... My tagline on 'Keeping Up' was, 'I’m the fat funny sister,' if you look at the opening of the show. The fat funny sister is 12 years older than her chronological age."