How You Keep Fat From Dying With BBL, Should You Eat Fatty Foods?

      Keeping pressure off of the areas of fat transfer is beneficial to maintaining the overall volume. Kenneth Hughes, MD

Dear SweetPeaches,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. In most cases 30-40% of transferred fat will be lost after few months. 
Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery  
Member, Am. Society of Plastic Surgery

BBL outcomes are entirely dependent upon graft viability and survival. The greater the survival, the more successful the outcome. These grafts are very pressure sensitive as pressure decreases local blood flow which then potentially compromises the graft take.
The recommendations for prolonged sitting/unrelieved pressure will vary from one physician to another. I generally recommend avoiding prolonged sitting for a month or so (with strict avoidance for 2 weeks post op). Occasional rest periods for sitting using a specialized pillow with escalating frequency and length are progressively integrated as a patient heals. I recommend patients work towards 1 hour total of seated resting per day by the 4 week mark.
Outside of the recommended offloading and pressure restrictions, patients need to aware that they should expect some measure of fat resorption (anywhere between 30 and 50%) irrespective. Maintaining a healthy diet is important as is avoiding exposure to nicotine, however, these are secondary to limiting pressure.
As always, discuss your concerns with your board certified plastic surgeon (ABPS).