What is likely to sag faster, implants behind the muscle or fat transfer/natural breasts?

Dear tastykakequeen,
it is not that simple as there is a number of factors that can affect your breasts. Generally speaking, larger implants will drop faster and they have an increased risk of sagging. 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

I appreciate your concerns however, the rate of sagging of a woman’s breast depends on factors like significant weight gain or loss, pregnancy, breast-feeding, and the aging process as well. Fat transfer to the breasts is usually only an option if one wishes to go up one bra cup size. Also asymmetry can be a problem as the transferred fat does not always take evenly on both sides. Breast Augmentation with round smooth silicone implants is a proven option with a long history of high satisfaction among patients. Come see me or another board-certified plastic surgeon in our area to explore the best options for you.

Breasts sag for numerous reasons. Some include genetics, skin elasticity, weight of the breasts, weight gain or loss, and hormonal changes. This can happen with fat transfer or implants. I prefer implants over fat transfer to the breasts as fat transfer can result in calcifications that can interfere with breast imaging.