"I work out almost every day," she tells PEOPLE. "I go to a trainer five days a week, and on the weekends, I do cardio and whatever I want to do."
Looking toned in a form-fitting Lanvin dress on Friday at 1 OAK Nightclub Las Vegas, Kardashian, 30, didn't share her current weight, because, well, a lady never tells. But she did share some tips for others looking to get in shape.
"I kind of eat what I want, but in portion control, which I never knew before," she says. "It's really hard. You have to train your body to eat less. Your eyes are bigger than your stomach."
She adds: "I had to train myself to drink more water. I drink like 5 liters of water a day."
Kylie Jenner, Kardashian's half-sister, recently told PEOPLE that she's "trying to drink a lot of water." Guess we know who gave her that idea.
"I yell at her and Kendall [Jenner] to drink more water," Kardashian says.
After all, she wants to be a role model for her younger siblings. "I don't want the responsibility for being that for everybody because I'm still learning and even when I'm 60 I'm still going to be evolving," she admits.
But her sisters are fair game. "I know what I can teach them, but it might not be for everybody, but it's for us. I want to impart the knowledge I have and they can take it. I think my job is to pass that on if it's in diet or whatever."