I think between hormones and water retention anything is possible. I have mine right now and I feel so bloated it's disgusting. Although, I never have stepped on a scale to measure the before and after weight loss/gain due to my period.  But you're young, with good metabolism, so an extra pound loss might just be your body burning fat and calories. Enjoy being 18, a pound and a half lighter, and having a fast metabolism.

Sure it makes sense. It's not only the weight lost after yor period, its also the weight you lost while you were bloated that you couldn't see at the time.

I gain about a pound or two the day I'm going to start, hold onto said pound or two for a couple of days, and then end up losing the amount I retained, and even some extra if I'm lucky.

My period-bloat is actually a good predictor for when I'm going to get my period, because my period doesn't start until mid-day, or even in the evening, but the morning before it starts I'm usually up a pound or two. It just sucks, because Mondays are my weigh-in days, and I started my period yesterday, so the period bloat is still sticking around. =( Hopefully I'll see 207 by the time this whole thing is over...

I gain a ton of weight right before my period. Normally I weigh a very steady 143lbs, but at the moment I'm closer to 150 with my PMS bloat. I retain tons of water weight for some reason, and the fact that PMS backs up my entire system doesn't help much, so I'm hoping that cranberry juice and an hour at the gym might help make me feel better and stop any cramps before they start :(

for me its about 2-3lbs of water weight. usually goes away by the end of my period.

If there's one thing I've noticed about that time of the month, it's that there's just no telling.  Sometimes it's a 4 pound difference overnight.  Sounds like you might have been on the verge of a slight loss before you started - that's happened to me before.

I'm 18 too and i just started having problems with water retention a few months ago.  During school i was normally around 110.  Then I shot up to 120 in a few days! It never occurred to me that it was water weight so I worked out and ate little and when i got off my period I was 108. I felt so good about myself that I ate a pound of m&m's and got right back up to 110 before I knew it. and on through to 115. lol.

I've actually asked a doctor this and the estimated weight gain around your period is 5 pounds of gas and water retention! Isn't that crazy? It makes me feel better though knowing that it's not sticking around!!

I'm reading all these.... and its my first time really calorie counting and watching my weight.  Its TTOM for me right now - so I'm kind of excited to see if at the end of this week or early next there  is a nice dip in the  scales for me.  hehe

I weigh about 3 pounds more than normal.  My solution is not to weigh myself a few days prior, during and I wait a few days after.  Even though I KNOW the cause - it still stresses me out to see the number on the scale go up instead of down. 

3-5 pounds isn't unusual for me at all.

yep..i usually gain between 4-6 pounds..it sucks...but it goes away ;)