Originally Posted by BostonKate

You're dehydrated. The rule of thumb for water intake for us big folks is this: take your weight in pounds, divide in half - the resulting number is the ounces per day of water you need to maintain a hydrated balance. The number will freak you out, but it is unlikely to lead to hyponatremia (water intoxication/poisoning) if you spread it out during the day. If you drink it in 2 or 3 big sessions, you may really mess yourself up.[This equation comes from multiple nutritionists I've consulted, as well as the medical panel for Weight Watchers USA, which had this printed in the meeting materials for a while as well as publishing it in the magazine. It is not Internet quackwash.] Add 8 ounces for every 30 minutes where you're exercising and breaking a significant sweat.

Oddly enough, drinking more water will help you lose weight faster. Metabolism becomes much more efficient when you're hydrated, you've got higher blood volume to shuttle wastes out, and your joints will be better lubricated so working out won't hurt as much.

Increase your water intake slowly so your kidneys and urinary tract get used to the load, though. Nothing says "worker with a medical problem" like a guy who's guzzling water and trotting off to the can every 15 minutes!