Kim and Kourtney Kardashian Collect Their Own Sweat to Find Out Who’s Healthier -- Watch! (Exclusive)

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Kim is on a mission to prove to Kourtney that her gluten-free lifestyle isn’t doing her much good on the next ‘Keeping Up With the Kardashians.’

Kim and Kourtney Kardashian are taking Keeping Up With the Kardashians somewhere it’s never been before: the sauna.

ET has your exclusive first look at this week’s all-new episode, which finds Kim on a mission to prove to Kourtney that her ultra-healthy, gluten-free lifestyle isn’t actually benefiting her that much. To prove her point, Kim challenges Kourtney to a “sweat test,” alongside pal Jonathan Cheban. According to Kim, they can collect their own sweat in vials and have it sent off to a lab to be tested for various toxin levels.

“Gluten, with a sweat test?” Kourtney asks, skeptically. “I’ve never heard of it.”

“I’ve never heard of a ‘sweat test,’ and it just sounds gross,” she adds in a confessional. “But, we do some pretty crazy things to get the information we need, especially when it comes to, like, beauty and health. So, I am definitely willing to do Kim’s test to prove that I’m healthier.”

In order to collect enough sweat for the test, Kim, Kourtney and Jonathan head into a sauna -- wearing thick bathrobes -- and slowly let their skin drip into the vials. Watch: