I Was Told the Best BBL is when the Fat is Only Harvested from the Back. Does It Make a Difference Where the Fat Comes from?

In my experience the area of fat removal has no bearing on the success of fat survival after transfer.  Furthermore, I have not read any scientific literature that would support better success rates of fat survival depending on fat's site of origin.  It matters more how the fat is harvested and handled versus where it came from.

Although the answer is not in completely, it makes some sense that the donor areas from places that are fat out of proportion to the rest of your body will probably have fat cells that retain these features after transplantation. Therefore any place you have unwanted fat would be a good choice

The success of the surgery is not determined by where the fat was removed; instead, it depends tremendously on the surgeon’s technique, surgical protocol, and postoperative instructions.In order to harvest enough fat for the Brazilian butt augmentation procedure, fat is removed where it is excessive. I routinely remove fat from the abdomen, flanks, upper and lower back, and thighs. You can even remove fat from the arms.


Fat does not handle stress very well and, if the surgery is not done properly, then, you will waste your money and will have suboptimal results.
 

Hello dear!
Thanks for the question and provided information as well.
Fat can be harvest from many areas: arms, abdomen, back, flanks, thighs, etc. But overall, what gives you the best results is removing the fat from where it needs to be removed. 
In general, you need to be physically healthy and at a stable weight, have realistic expectations, be a non-smoker and your BMI needs to be 30 or less.
l recommend you to make an appointment with a board certified plastic surgeon to talk about your goals and anything you need to know.
Good luck :)

There may be different definitions of what is included in the Brazilian Butt Lift, but my experience, what gives the overall best results is removing the fat from where it needs to be removed.  I have performed this procedure for about 14 years now and have rarely come across a patient (who was a candidate for this procedure) that didn't need to have fat removed from the abdomen, waist and flanks (low back area).  I often remove fat from other areas as well, such as the bra strap rolls, inner or outer thighs as well as the upper arms.  The fat can be taken from anywhere, as long as the surgeon has a good technique and the patient follows the post-op instructions given to them by their surgeon.