Apparently, researchers have found ways to grow a (very limited) number of new body parts for people who need them from their own stem cells. Nothing flashy (yet), but it shows where the tech could go. Ten-Year-Old Girl Receives Major Vein Grown From Her Own Stem Cells | Singularity HubSuppose it were possible to grow any body part they wanted. Could you gradually replace your whole body via body part transplants? Or maybe just your whole body minus your brain, so you could maybe have a 80 year old brain in a 20 year old body?
Even if you didn't have stem cells on reserve for you, I suppose you could just mix eggs and sperm until you get a few "compatible donor" stem cells. So maybe the 20 year old body isn't your own body (more like the body of someone that could have been related to you), but it is still young and strong.
Imagine some 60 year old woman who decides, instead of having a "face lift", to have young skin literally transplanted/grafted onto her face, so her face doesn't just look young. It is young. Would that just be the next logical step in cosmetic surgery?