I'm posting here because I suspect this is exercise-related...

Has anyone else messed up their periods doing this whole weight-loss thing? Mine was fine while I was eating fewer calories in April, May, June and most of July. Around mid-July I upped my calories by a few hundred as I started maintenance, and I got my period as expected in late July.

My August period was a no-show and is now almost two weeks late. I feel a a little crampy but nothing else. I just took a pregnancy test (even though my DH had a vasectomy last year - LOL!) and it was negative.

I just don't think I'm running that much. In fact, I'd say my weekday runs are shorter than they were for most of the spring/early summer, though my long runs are longer (8, 9, 10, 9, 12 the past few weeks).

I'm concerned that my body is saying that I'm treating it so poorly I'm not healthy enough to reproduce. Not that I want to reproduce, mind you (see vasectomy, above ) but I'm guessing I should take this as a sign?

Haven't had this problem but some high school girls I know who run cross country have had this problem. I think it actually relates to how low your body fat percentage goes. At 5'6" and 120 lbs you probably have a pretty low body fat percentage so that might be causing it.

My periods always get screwed up with changes in weight, diet, or exercise. The part that I hate worst is the unpredictability. Otherwise, I have a clean bill of health. My body is just sensitive to change. Definitely see your doc if you're concerned, though.

definitely a sign that your body is stressed out. I havent seen my period in over a year. Its probably the overtraining/undereating much more so than body fat levels.

MK, I've been in denial that I'm overtraining. I had headaches for a couple months (resolved now), a little dizziness for a couple weeks (resolved now), my heart rate is elevated (still up)... but I keep trying to convince myself that it's something else...

I have a half marathon this weekend and then I'm going to ease off -- though I need to get my food under better control if I'm going to do that. It will be hard to back off though, because I am loving the running right now.

get it under control NOW i would say. I took MONTHS off from training/dieting/running and i still didnt get it back. To be honest you might have to try eating at maintence for a little bit WHILE you back off training, eating carbs, doing re-feeds, etc..... are you weight lifting? If so you might want to back off ANY form of supersetting or full-body workouts-- they can be very rough on those of us who are "sensitive" to overtraining.
What sux about being overtrained is we dont realize we are, untill something BAD happens