Will I "undo" my lower face lift if I lose weight after the surgery? Should I try to lose the excess weight before?

It's difficult to predict how this will effect results. It is recommended to lose weight first before undergoing your procedure. To improve final results, we will often do ultherapy about 4-6 weeks after facelift to get more of an outcome. See an expert. Best, Dr. Emer

If you are going to be losing weight, I would recommend doing this before having your lower facelift.  If you lose the weight after the surgery, it could affect your results.