Fat transfer to face, for naturally skinny people who burn fat easily/ fast metabolism?

Hello and thank you for your question.  The
best advice you can receive is from an in-person consultation.  Fat grafting to the face can have permanent results.   Make sure you specifically look
at before and after pictures of real patients who have had this surgery
performed by your surgeon and evaluate their results.   The most
important aspect is to find a surgeon you are comfortable with. I recommend
that you seek consultation with a qualified board-certified plastic surgeon who
can evaluate you in person.
Best wishes and good luck.
Richard G. Reish, M.D.  FACS
Harvard-trained plastic surgeon

Transfered fat cells do not "burn off". Initially there is swelling and injured cells that don't survive. This is true for and transplant or tissue graft. What is present after the grafted area has completely healed will be there for decades.