The 36-year-old actor said she always felt feel "unsafe" if she expressed herself "sexually", Contactmusic reported.
"A countdown was started on my local radio show to my 18th birthday, euphemistically the date that I would be legal to sleep with.
"Movie reviewers talked about my budding breasts in reviews. I understood very quickly, even as a 13-year-old, that if I were to express myself sexually I would feel unsafe and that men would feel entitled to discuss and objectify my body to my great discomfort," Portman said.