Exercise and weight gain

ok, so im not going to start the ole Muscle wieghs more than Fat debate....however..

over the last month i have started a pretty rigerous exercise program.... 45 mins of cardio with weight vest and 60 min's of upper body lifting x5 week.  ive notlced Im averaging a 3lb - 5lb weight gain from my lowest most days...I fluctuate and im sure thats water retention in my muscles..... but i was wondering what everyone elses experience has been with this. 

I'm also needing to eat more... like every 2 hours i need something for fuel. 
Im getting my Body Fat % and RMR tested in a couple weeks so that will be a good gauge as to where i am at. 

Just wondering what your experience has been?

Thanks,
kate

I think that those numbers seem pretty realistic if you have been working out hard for a month.  3-5 lbs seems like a pretty healthy gain to me.

The 3 times that I have started marathon training programs, I have gained an average of 8 lbs.  I am sure that part of it is muscle but mostly, my appetite goes through the roof.  I think about food from the minute I wake up to the second I go to sleep.  About a month after the marathon, the appetite becomes more realistic and I can contol it better.  Heavy exercise definitely makes me eat more.

BTW, do you run races at all.  I love running in Northern New England.

Thank you for your response...Im glad the hunger is legit and not in my head! 
I haven't run any races yet.... Currently i am training for the Firefighter physical agility exam.  I take it in 7 weeks down in CT, so im working out 5 days a week at a pretty intense pace.  I have to say though after constantly losing weight for the last year its a hard pill to swallow to see that number go up again...plus the constant need to eat freaks me out!!!!!! 

ive never been much of a runner but I am hoping to run the Red Hook 5K memorial day weekend In portsmouth.  Im sure that is WAY below anything you would run around here :)  hopefully someday I can do the market sq day 10k. 

K8