Final answer:
Breast sagging is not caused by breastfeeding but is influenced by aging, weight changes, gravity, and smoking, which affect the supporting structures of the breast tissue.
Step-by-step explanation:
While breastfeeding does not cause breasts to sag, factors such as aging, gravity, weight fluctuations, and smoking have been identified as contributing to breast sagging over time. The ligaments in the breast, called Cooper's ligaments, are responsible for supporting the breast tissue. Over time, these ligaments can stretch out, and when combined with the skin losing its elasticity due to aging or significant weight loss or gain, sagging may occur. Moreover, smoking can contribute to the loss of skin elasticity by breaking down the skin's collagen. While lactation and breastfeeding involve hormonal and physical changes, including the expansion and contraction of milk glands, these are not the primary causes of sagging.