Gaining weight from working out

I have been training for a few triathlons this summer and have gradually increased my training over the past four weeks (or so).  The biggest change is that I have increased my cycling/spinning to about 5-7 hours a week and I still run for 60 minutes three days a week as well.  Since increasing this, I seem to have gained 6lbs (on a good day). 

I am very discouraged because I work out more than anyone I know but my pants are getting tighter around the legs.  I have even noticed my arms are getting flabbier. 

I am eating 1200-1500 calories a day, scoring an "A" nearly every day, and drinking tons of water.  WHY won't my pants fit and why am i gaining? 

Grrrr! :-)

I am muscular, and my pants are a lot bigger than a lot of my friends, just because I have huge, muscluar legs, which are strong and sexy, I might add.  This is even taking into consideration that my friends and I weigh about the same.  (I was a 9 at this point, she was about a 6, we were both 150)

Your body is breaking down your upper body muscles and using that energy to fuel your intense cardio vascular/lower body exercise. That's my armchair speculation.

I have to keep myself in check in regards to my body breaking down my muscles during my cardio-vascular workouts (I'm training for boxing); I usually drink A LOT, 400-500 calories worth, of powerade or gatorade, something with electrolytes and sugar, during those training sessions, as those carbs get burned off pretty quickly and my body doesn't have to resort to breaking down muscle tissue for energy.

So do you think I should I be drinking more gatorade or propel during my workouts? 

I don't think you're eating enough.  What does this website say you should be eating?  This is my armchair guess - you're burning off muscle and gaining fat.  If you'll increase what you're eating, and especially eat before and after a workout, I think you'll see some positive changes...and won't gain weight when you go to maintenance mode. 

Check this out.

C:\Documents and Settings\richardson\Desktop\Get The Skinny On Fat  Articles  Fitness  Health & Fitness  Sympatico - MSN.htm

Also, I would eat a small amount of protein 20 mins before and soon after working out, even if you don't feel hungry.  This will help your body to not cannabalize itself.  Maybe a whey protein powder will help you out.  I notice that I get flabbier if I don't drink one after intense workouts.

thanks for the suggstions guys!

anyone else having the same problem?! : (

I have the same problem ,my thighs became bigger and my triceps became flabby,I stopped running but I still walk around 10 hours weekly ,I am trying to work out my triceps as much as I can with no good results.

muscle = heavier than fat!!!

And if you don't eat enough, your body can't produce enough fat! If your body can't produce enough fat it will take your muscles more likely than your fat reserves(cause they will be kept for the worst case of you stopping eating anything, just to hold you alive).