While occasional use of a mild diuretic might be helpful in getting the body to excrete excess water through the urine, it is not effective as a long term treatment (and as we know, most coffee drinkers are in it for the looooooong haul). When you repeatedly take a diuretic, the body eventually responds to the continual dehydration by learning to retain more fluid than usual. This is why people with eating disorders (who abuse diuretics, laxatives, etc) are at an increased risk of edema. Once use of the diuretic is discontinued, the body continues to retain excess fluids until it learns that adequate fluids will be regularly available.  This usually takes anywhere from 3-6 weeks. You can read more about the effects of diuretics on edema at the following link:  Edema (Water Retention) from Diagnose-Me.com

I'd love to know your thoughts on this line of reasoning. Do you think it makes sense that a daily diuretic could lead to fluid retention? Thanks for your challenging comment!