Your body is 70% water. So maybe there is some truth to this. From my personal experience, staying fully hydrated helped me keep my blood pressure low. I also know one time I tried drinking four cups of water first thing in the morning to lose weight. It did help me lose weight. Of course, it was not easy keeping the water down at first, but after a while, you’ll get used to it. However, I don’t know whether it’s the water effect or because after drinking four cups of water in the am, and getting nauseous, you probably won’t feel like eating anything for the rest of the day. Either way, it worked!