From the perspective of modern cellular science, fat from the anterior abdominal wall is richest in mesenchymal stem cells. Therefore, it makes sense that if we harvest small amounts of this fat with cannulas, we get a good mixture not only of adipocytes but also of stromal cells — the cells located between fat tissue. These stromal cells contain many stem cells that can differentiate into blood vessels or fat cells themselves.
Other good donor areas are regions with finer fat that is more suitable for the breasts: the knees, the area above and around the knees, and the lower back. Sometimes fat is harvested from the “saddlebag” area, but it is denser and less favorable for graft survival.
In terms of priority: anterior abdominal wall, lower back, and knees, depending on the amount of fat needed.