How long does it take for fat to settle after a bbl? How long do you have to wait before sleeping on your back?

After a BBL, there will be some swelling on the buttocks, that slowly goes away. In many cases, the patient thinks that the fat is disappearing, but most of the volume lost, is from the swelling that is going away, and usually in the first month is when the patient notices the biggest change in volume, and then in the following months the amount of change is much less. Not all the injected fat survives, and also the percent of survival is different among patients. In my practice about 30 to 40% of the total injected volume goes away 3 months after the surgery. To preserve the blood supply to the injected fat, the patient should avoid any pressure on the buttocks, for at least 2 weeks, that it is the time, the injected fat needs to get new supply and survive. Even after that, it is recommendable to avoid sitting on the buttocks, for long periods of time during the first 4 weeks, so sitting on a memory foam pillow it a good idea, and taking breaks from sitting, every 15 minutes is another way to avoid too much pressure on an specific are of the buttocks. Check with your surgeon, for specific instructions.

Thank you for your question.

Fat survival after fat grafting depends on a few things such as technique used, anatomy, genetics, post operative care etc. Best case scenario, usually about 70% of the transferred fat will survive. Within the first 6 months, about 30% of the fat cells will not survive and will be reabsorbed and passed through your body. Whatever fat is remaining after 6 months, is what will remain as long as your weight remains stable. I recommend that my patients do not lay/sit on their bottoms for long periods of time for the first three weeks. The first week I do not recommend any sitting or pressure on the buttocks, days 8-14 the patient may sit up to 5 minutes two times per day.  Days 15-21 the patient may sit up to 9 minutes five times a day only then days 22 and beyond sitting is fine as long as the patient is comfortable. If you must sit on your buttocks for longer period of time before 3 weeks, I definitely do recommend purchasing a  BBL pillow and getting up every 10-15 minutes to walk around until you are at least three weeks post op.  Best of luck.
Sincerely,

James Fernau, MD, FACS
Board Certified ENT
Board Certified Plastic Surgery
Member of ASPS, ASAPS, ISAPS, The Rhinoplasty Society, AAFPRS, OTO/HNS, ASLMS, International Federation for Adipose Therapeutics & Science