Should I be gaining weight for breast fat transfer?

Dear Adventurous496391,
generally speaking, you want to reach your goal weight before you consider a surgery, otherwise your results will be suboptimal if you continue to lose weight after the surgery. If you are considering surgery, I would suggest you consult a board-certified plastic surgeon. Only after a thorough examination, you will get more information and recommendations.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

Fat transfer to the breasts is a great option to moderately increase the size of your breasts without having any telltale signs.I don't recommend my patients to gain weight because when you lose the weight the fat will shrink.It's ok to gain weight after the procedure as the fat in your breasts will get bigger, which is what you want.

I believe you should be at your average weight. If you gain weight for a fat transfer you'll lose it after and the net result would be the same had you not gained weight.