All that organic, gluten-free eating is paying off!

Kourtney Kardashian dropped by the studio to film Keeping Up with the Kardashians yesterday, and the reality star rocked tight maroon leather pants with a skimpy tank top and snakeskin boots. She's almost 40, but clearly she's not going to listen to people telling her to dress her age!

The mother-of-three follows a very strict diet and exercise regime, but some friends and family think she's taken it too far.

A source tells X17:
    "Kourtney is obsessed with her body. She says she's eating "clean" to stay healthy for her kids, when in reality she's just trying to stay young and hot for Younes. She's head over heels for him, and she's terrified that he will leave her when she's past her prime. She's rapidly become the most image-obsessed of all the sisters."

We hate to admit it, but she does look bangin'!