Would a fat transfer help me with more fullness, improved cleavage, and under-boob without getting implants? (photos)

Breast fat transfer is a great tool to balance breasts, improve symmetry, and gain up to one cup size in volume.  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.  I place one incision under each breast and the fat can be injected to the locations specified by the patient.
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.

Thank you for your question and photographs.  Fat transfer for improved fullness and shape of the breast is an option in some situations.  There are limitations with how much can be transferred and how much of that will survive in the new location.  There may be a need for multiple procedures to achieve the desired outcome.  All of those concerns can make the decision more difficult.  Having a consult (or two) with a Board Certified Plastic Surgeon that has experience with these procedures will help you decide.  You would likely have a very nice result with a standard augmentation.  Best of luck.

Don't try to gain weight before the transfer, since you may tend to loose the weight after the transfer. If you would be content with a half to one cup increase in size, then the transfer might work well for you. If you want to be fuller, implants would be best. Implants are more consistent with size, since not all the fat transferred survives.