With a BBL, is there a chance for rejection of fat?

Hello, thank you for your question. You would never reject the fat, as it is your own fat that's being injected. Rather than that, you should keep in mind that it is live cells that we are transpositioning, and those cells have to survive for a couple of days on the surrounding oxygen and nutrients that the other native cells are not using, until the body creates new blood vessels to nurture this live transpositioned cell. Some cells will not survive, it is a fact, and depending on technic and your body's ability to create new blood vessels, that a higher percentage of cells survives the transposition. Hope to have been of some help. 

I would not say specifically that fat is rejected, but rather some fat may not "take."  Usually the material that does not take gets resorbed, but thre is a risk of fat necrosis or drainage.