Kim Kardashian Has One Very '97-Year-Old Granny' Habit

Kim Kardashian
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Kim Kardashian West's early morning walks aren't for everyone!

In a new promo for Sunday's Keeping Up With the Kardashians, the 37-year-old reality star's seemingly simple exercise routine gets ripped by her best friend, Jonathan Cheban -- until she puts him to the test. 

"I'm really impressed with your self-control. I think it's really good," Jonathan tells Kim in the clip. "It shows me that you are possibly thinking of changing a lifestyle." 

"By the way, this is pretty good for somebody who eats 365 meals a day," he adds of his body. 

WATCH: Kim Kardashian Enjoys a Few Slices of NY Pizza Before Diet: ‘This Was So Worth It!'

"But if you worked out…" Kim teases, before Jonathan goes all out on her morning walks. 

"I go to the gym. All you do is walk up and down hills. You're like a 97-year-old granny," he jokes. "Every morning I'm in New York I see, ‘Here we go! I'm going walking!' Every morning I'm like, 'Where's the exercise?' I wanna see the Golden Girls up and down the hill."

As Jonathan soon finds out, however, Kim's workouts aren't so easy. 

WATCH: 'KUWTK': Kim Kardashian Mocks 'Desperate' Scott Disick for Taking Bella Thorne to Cannes

Keeping Up With the Kardashians airs Sundays at 9 p.m. on E!

Kim's hard work in and out of the gym definitely pays off -- and Jonathan knows it. See more in the video below.