Why don't fat transfers stick in breasts?

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.  Multiple transfers would be required for additional cc's.  In general, the abdomen and thighs are preferred donor sites but fat from other areas can be used.
Some of the retention rate will depend upon the amount of fat transferred, as smaller volumes will likely have a higher survival.  Occasionally, a patient can resorb a great deal of the fat despite optimal transfer procedures. I typically transfer from 250 cc to 400 cc or so per breast.  Thinner patients are outstanding candidates in my opinion, because the fat transferred is extremely resistant.  
Results are largely dependent upon the skill of the surgeon, his/her ability to remove fat without creating contour deformities, and your expectations. You would need a consultation with a board certified PS to determine your available fat stores.

Dear realbooty98,
fat transfer breast augmentation is a viable alternative for women who desire larger breasts without the use of implants. Fat transfer is also widely used in reconstruction of the breast after a mastectomy or lumpectomy. It can also be very effective in correcting the size and shape of the breasts due to genetic problems such as tuberous breast or Poland Syndrome, two conditions that look like misshapen or underdeveloped breasts.In addition, the following scenarios are also reason to consider breast fat grafting:• If you have chest areas that appear creased and sunken• If you desire more permanent correction than is provided by temporary fillers• If you wish to improve your body contour, revise scars, fill bodily depressions and rejuvenate the natural curve of your breasts• To fill in contour irregularities or hide obvious signs of breast implantsYou should discuss your concerns with a board certified plastic surgeon and make sure your surgeon understands your concerns and your breast augmentation goals. Only after a thorough examination you will get more information and recommendations.
Daniel Barrett, MD