Hi Siltz,
I switched to low carb during my time as a body builder and I actually found that after I've got into ketosis I actually had more energy and less fatigue such that I cut my session time down from just under an hour and a half to between 25 and 30 minutes doing the same number of reps with the same weight and in fact the gym instructor used to follow me around because he couldn't believe what I was doing in the time I was doing it in. I think if he would've had his way, he would've had me dope tested.
The only thing I would say the quality of protein that you are taking if you're doing any form of serious exercise has to be high. I know a lot of people resort to whey protein shakes but I would tend to steer away from those because of the other ingredients they contain, things like soy and various artificial sweeteners.
Honestly the best protein you can take if you're exercising to that sort of degree is good old fashioned grass- reared beef. I also agree with Doug wholeheartedly, you should give your body time to rest and also make sure that you're not just drinking water but remember to make up the salts, literally with salt but don't forget to dose up with potassium as well.
Hope that helps,
Mark