This depends on several factors, including but not limited to your health, amt. of fat present, complications after surgery, and the overall goal. Usually a time period of a year is advisable, but this decision should be made with your Board Certified Plastic Surgeon and you in a consultation.
There is no set time to wait. Mostly it depends on how rapidly you are up and around after your major surgery. Assuming it is other areas of the body that are being treated you should be OK in a month or so.