Does age affect whether fat cells survive? I'm 46 yrs old and was told that because of my age BBL would not be recommended.

I believe your overall health, lack of medical issues and the techniques used by the surgeon to perform the fat transfer are the most important determinant in fat survival.  If there is a difference as one ages it is probably a small difference compared to the influence of the factors I mentioned above.  I hope this helps.Thomas Taylor, MD, FACS

More important than age is the technique used during a fat transfer procedure. Depending on technique the amount of fat cells that permanently survive can vary between 50-70%. You should certainly discuss this surgery with your primary care physician to seek medical clearance before having any surgery. Consult with a few plastic surgeons in person to review your goals. Almost all patients can an improvement in their shape with this procedure.Best wishes,Dr.Bruno

Hello and Great Question.  I appreciate the time you are spending researching this procedure.  My name is Dr. Matthew J. Nykiel.  I am a Board Certified Plastic Surgeon, a Fellowship Trained Cosmetic Surgeon, and a Butt Augmentation Specialist.
In my opinion, the answer is Yes.  I do notice that as individuals are older the fat transfer is not as good as someone who is younger.  I typically start to have that conversation with patients around the age of 50 years old, some earlier and some later it depends on their goals and the quality of tissue for us to use.  I am not to saying that I will not perform fat transfer on older patients; I absolutely will; it is just a realistic discussion I have with patients so we both have realistic goals.  I think when you take a step back and think about it, it makes complete sense.  We know for a fact that a portion of the fat transferred does not stay, it is pretty logical to think that the 20 year old is going to have a better "take" ratio then say a 50 or 60 or even 70 year old.  
Again that is not to say that you are to old; I absolutely do not think you are too old and I agree with all the other doctors answers that you can still have a great result.  However, I also notice none of the answers provided answered your question:  does age affect fat transfer take rates?  In my opinion, yes it does.  As long as you know that and are aware of it, I think you are absolutely fine to have a fat transfer provided you and your surgeon discuss your goals and determine if your goals are potentially achievable.  
I hope that helps!  Best of Luck!
Matthew J. Nykiel, MD#TopREALSELFDoctor#CoreREALSELFDoctorButt Augmentation SpecialistLiposuction SpecialistBoard Certified Plastic Surgeon