Sources close to Lopez tell us she'd been hospitalized in Las Vegas and died over the weekend as a result of heart complications. A rep for BBC said in a statement, "We regretfully announce, with great pain, the passing of The Founder & Owner of Babydoll Beauty Couture, The Legendary Jamie Lopez. We ask, on behalf of the Babydoll family, that you allow us time to process this tremendous loss."

Lopez, who at one point weighed 846 lbs, designed her salon while confined to her bed -- too heavy to get up and see the world. The show followed her progress, including her 400 lb weight loss, and her first time walking inside the salon.

Babydoll Beauty Couture was founded to service plus-sized women ... and "Super Sized Salon" -- which premiered earlier this year on WE tv -- highlighted both the salon's staff and customers. We are told she was just about to begin filming for season 2.

Jamie was only 37.