Jenny Craig -- We'll Pass On Kim Kardashian's Pregnant Ass

Two major weight loss companies won't touch Kim Kardashian's "big fat ass" with a 10-foot pole ... TMZ has learned they have zero interest in signing the pregnant celeb to a Jessica Simpson type deal.

Reps for Jenny Craig and Medifast tell TMZ they won't be be helping Kim K shed her post-baby weight -- and their reason, ironically enough, is the reality TV star isn't real enough.

Interestingly, JC's rep added, "We will continue our working relationship with Mariah Carey."

Of course we don't know if Kim's even looking for a new weight loss deal ... she endorsed Quick Trim last year.