Excerpt from Dr. Simeons original hCG diet manuscript, Pounds and Inches. This is from section 54 on the topic of Water while on the HCG diet protocol.
Patients are usually hard to convince that the amount of water they retain has nothing to do with the amount of water they drink. When the body is forced to retain water, it will do this at all costs. If the fluid intake is insufficient to provide all the water required, the body withholds water from the kidneys and the urine becomes scanty and highly concentrated, imposing a certain strain on the kidneys. If that is insufficient, excessive water will be with-drawn from the intestinal tract, with the result that the feces become hard and dry. On the other hand if a patient drinks more than his body requires, the surplus is promptly and easily eliminated. Trying to prevent the body from retaining water by drinking less is therefore not only futile but even harmful.