If 400cc of grafted fat from abs and back is injected into each side of the breasts, how much is likely to survive?

In general, 200 cc per breast is typically the upper limit of fat injection recommended by most plastic surgeons.  It is not that more cannot be injected; but on average, this has been determined to be the most that can be expected to live during one transfer.  The fat must be injected through multiple planes in small amounts to the tissue through one tiny incision under each breast.  
Fat transfer to the breast could improve the fullness of the breast, particularly at the top of the breast. If you want more than a one cup size increase, implants are probably a better choice.  If you want fat grafting, this may require multiple treatments to reach the size you desire.   About 50% of the fat obtains permanence.  
Kenneth Hughes, MD, Board Certified Plastic Surgeon
Los Angeles, CA

In most cases you should expect a 70% survival of the fat.  That would be about 280cc for a 400 cc transfer. You can put more in the upper pole and shape the breast more with fat than with an implant.  I would be more focused on shape and not so much in size.   If your goal is all size I would advise you to put in an implant.

Good question Angeline.  One of the drawbacks of fat transfer to any part of the body, but particularly the breasts or butt, is prediction of the amount of fat that will survive. I usually recommend fat transfer for breast augmentation in patients who only desire to increase their breast size approximately one cup size. It is unlikely that enough fat will survive to increase more than that. Also there can be an issue with symmetry, as fat survival is not always equal for each breast. After 4 to 6 months you will have a good idea of how much fat survived. Best of luck.

Dear angelinelovelace,Fat viability depends a lot of surgeon technique. The fat has to be placed back as soon as possible so that it has a greater chance of survival. It has to be placed carefully so that not too much fat is placed in only one area. If you are considering a surgery, I would suggest you to consult a board-certified plastic surgeon. Only after a thorough examination you will get more information and recommendations.Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

is very dependent on your surgeon's technique and how the fat is harvested.  In my experience, my patients get about 60% to survive.   The key is to have a blood supply established to the fat in the first few weeks and movement during this time is detrimental for fat to take, in addition to bouncing or other vigorous activities.