There's really not a way to avoid water retention, other than to monitor your sodium intake. Increased exercise causes water retention as a matter of course, and it's a *good* thing, and temporary. It's explained here: www.sparkpeople.com/community/ask_the_expe
This water retention can mask fat loss, but as I said, it's temporary and unavoidable.
I also wouldn't worry about the hot yoga class; it burns the same amount of calories as the regular style of yoga it mimics. Adding heat doesn't make you burn more calories, it just works your heart harder, and you can't trust any heart rate monitor estimates you may have.
If you are always tired, I'm definitely concerned you may be overtraining or underfueling (or both.) Check out this article for more info: www.sparkpeople.com/resource/fitness_artic
Jen has great advice, and is the go-to Coach here for endurance training running. :)
Edited by: DRAGONCHILDE at: 3/2/2013 (17:10)