There is a very informative website, Elements4Health, which I encourage everyone to follow.  Today and article showed up entitled The Importance of Drinking Water, which describes how drinking too little water lowers the metabolic rate and negatively impacts kidney and liver function, and leads to reduction in the metabolic rate.  Indeed, I am one who is somehow able to get by on too little water, but I have noticed that when I drink more water, I do feel better!  One rule of thumb is to drink 1/2 your body weight in ounces daily.  So, a 160 pound adult would drink 80 ounces daily.  This does seem like a lot of water.  But then again, in our culture we think 6 hours of sleep should be enough (which is NOT true).