After the Brazilian Butt Lift surgery, the patient must not put pressure on the fat grafts for a period of 3 weeks. Ideally, not sit at all on the new fat grafts for 3 weeks to allow a full 'take.'
Why 3 weeks? These are the key things that must happen for a fat graft to be successful:
Blood supply must reach the fat graft before it runs out of nutrients.
Blood vessels must get incorporated into the graft successfully.
All the tissues- fat grafts, blood supply, and surrounding tissues must be knit together successfully by the extracellular matrix.
It takes 3-4 days for the blood vessels to grow into the fat grafts. During the new few days, the blood vessels begin to strengthen. The extracellular matrix surrounding the fat graft takes another 2-3 weeks to reach enough strength to withstand minor stresses. This is why 3 weeks is the absolute earliest a patient can begin stressing the tissues.
Plan to spend the 3 weeks mostly resting on your stomach or sides, getting up occasionally to limber up the muscles, but avoiding things that place stress on the healing tissues.