Water Retention

Question
I have been marathon training since April.  I was a sprinter in college (10 years ago), I play recreational soccer and have had two children, most recent Feb.6.  For some reason (and this is my question), I retain 5-9 lbs. of water weight after a run over 12 miles.  Saturdays are my long run days, and I will weigh about 141 (I am 5'8), and on Sunday, I will weigh in at 148.  By Friday, the weight is gone, but it starts over Saturday when I do my long run.  Is this normal, or could there be some seriously wrong with me physiologically?  I am 33 and think in good health.

Answer
Arika,

I don't know why you suddenly weigh 7 pounds more on Saturdays all the time. The only thing I can think of is that you overhydrate before your long runs.It's very interesting to me. i don't think anything is wrong with you, however, if it really scares you I would recommend seeing a doctor.

RYan