Low dietary energy intake often results in low calcium intake among other things. Calcium is an essential mineral for healthy bone deposition & strength. The combination of low estrogen with low calcium intake can lead to:

• weak bones
• poor bone formation
• increased susceptibility to stress fractures (amenorrheic athletes are at a 2- to 4-fold greater risk compared to normally menstruating athletes)
• premature osteoporosis

With increasing numbers of missed menstrual cycles, bone mineral density drops. Loss of bone mineral density is largely irreversible.