How much can losing weight after a BBL affect the procedure? I've lost about 10lbs after my BBL.

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.
Weight loss can certainly effect the entire body, so does weight gain.  If you happen to lose weight, the effects would be spread throughout your body, affecting the transferred fat too and causing the cells there to shrink.  As the buttocks lose volume due to weight loss, it could affect BBL outcomes.
On the other hand, weight gain will make all the fat cells in the body expand, including the transferred fat cells. This happens as the calories turn into fat that is stored in the cells. This clearly means you can expect that your butt would gain volume with weight gain. So if you have experienced weight loss after BBL and want to restore the results, you need to gain weight carefully. This can help restore the attractive derriere you achieved through the procedure.
I hope that helps!  Best of Luck!
Matthew J. Nykiel, MD
#CoreAesthetic
Butt Augmentation Specialist
Liposuction Specialist
Board Certified Plastic Surgeon

Dear leila777,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
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

This is a good question, unfortunately without an exact answer. We do not know exactly how transferred fat cells respond to weight gain or weight loss.To my experience transferred weight, once fully healed, is rather resistant to weight fluctuations. However, there might be exceptions so my advice is bring the weight down slowly and avoid any crash-dieting. Then you should be able to preserve your results quite well.