What is the cause for fat and volume loss after a BBL?

Dear AD17,I instruct my patients not to sit for 2 solid weeks. We provide them a specialized pillow that our patients can sit on during that time. They can sleep on their stomachs or sides. Fat viability depends a lot of surgeon technique. The fat has to be placed back into the buttocks as soon as possible so that it has a greater chance of survival. It has to be placed carefully so that not too much fat is placed in only one area.Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

Not all fat survives fat transfer. Fat transfer technique is what is important for successful fat transfer. I recommend water-assisted fat harvesting which gives pure fat to transfer and combine with platelet rich plasma (PRP) to get the most viable and sustainable fat cells. I then combine with Sculptra, depending on area, to improve final results. recommend getting a formal evaluation with an expert. Best, Dr. Emer

Dear AD17, BBL/IPL treatment should not cause significant changes in facial volume - at least this is not among the well known complications and side effects of this type of light treatment.  Certainly unusual outcomes can occur but loss of facial fat volume may more likely be the result of something else (e.g. radio frequency treatments, metabolic changes).  Elevated temperature certainly does induce fat emulsification and fat cell destruction (lipolysis) but both the temperature and length of time required for this to happen are not achieved during typical BBL/IPL treatment sessions.J. David Holcomb, MD

BBL targets superficial brown and red spots. It should not cause fat atrophy. Volume loss associated with BBL treatments is most likely explained by other treatments done around the same time as BBL. 
Razieh Soltani, MD

Great question! There could be some reasons behind fat resorption following transfer: #1. Over injected volume cause higher interstitial pressure leading to decrease diffusion of oxygen to fat cells causes their death. #2. To dilute volume saline to fat instead of pure fat being transferred. Than saline reabsorbs leading to decreasing volume appearance. #3. Infections. These are just afew basic responses not in detail .