Your 4lbs a week is more like a wrestler cutting weight-I know water drops off fast, but you should have hit your water equilibrium oh, like 2 years ago or so with constant activity. I'd shoot for 2, maybe 3. That extra pound is coming from somewhere and if its not fat it can throw your hormones all off and really mess with some functions. Here is another possible thought-hyperhydration? I know you are losing it when you ride, but when you are just sitting and whatnot, too much water too quickly can dilute your blood and lower your blood pressure-it throws off the potassium ion balance in your heart and you get arrhythmia and can die.