well I didn't know IUD existed that didn't have hormones. The copper one sounds like what I need. Hormones drive me crazy. No birth control seems to work. Its all caused bad side affects. I most likely wouldn't use the copper IUD either. I'm chicken.

But to answer your question. Your body does require about 500 more calories during your period. and during the time of ovulation. It's back to the cave man theory. If the opportunity for you to become pregnant is near, the cave man theory insures that you will be well nourished and your body be able to support a fetus. That is why one gets starving hungry every month like that. The cave man theory was great when there were cave men, not so grate when every modern cave woman takes birth control.