Lots and lots of people experience this prior to or during their periods, and I don't think anybody really understands why it happens, though there's plenty of guesses. The important thing is it always passes in a couple of days, so whether you're able to tough it out or whether you consistently "blow it" it's not going to have much effect on your weight in the long run. You will be fine, however you choose to deal with it, as long as you don't let it mess up your head.
For myself personally I find that simple awareness of what's going on ("oh, it's THAT thing again") helps immensely in keeping the nibbles from taking over. Since I know it's not going to last forever, it's not that difficult to just focus a little bit more on good food and good habits on those days, and then soon enough it's gone. I don't worry overmuch about calories (again, just a couple of days, no big deal), but I do try to pay extra attention to those other things, for the discipline and positive reinforcement of it.
There's a whole thread on this sort of thing recently that probably has some things in it that will help. The title is "bottomless pit".
Height 5'8 1/2"
5K 4/21/11: 31:55
|64 Maintenance Weeks