bbl and anabolic steroids - Was it a big mistake to lose a lot of weight 6 months after bbl?

Dear guapoeton123,
you will likely see your weight gain in a uniform distribution after a fat transfer to the buttock (Brazilian buttock lift). The weight or fat that you gain after surgery will not necessarily all go to your buttock area. Similar to weight loss, It’s important to realize that weight loss will affect the entire body, but it may affect the buttock in a more pronounced manner.
Daniel Barrett, MD

If you lose overall body fat, you will probably lose some of the fat in the buttocks as well.  In most cases of weight loss, the buttocks and other areas with stored fat will become smaller.  The fat will not move, but losses in weight will distribute differently. The fat that lives in the buttocks from the BBL will get larger with weight gain and smaller with weight loss.

Hi and welcome to our forum!
Following a BBL, we recommend that the patient be at their stable desired body weight at the time of surgery and maintain that weight after surgery. Weight fluctuation of as little as 10 pounds may have a profound effect upon buttock fullness. Fat cells are not "killed" by weight loss. The cells lose their volume but remain viable. Weight gain should restore the volume. 
Best wishes...