If you drink 16 cups of water a dy how much weight would you lose?

Doesnt really work that way.

While drinking enough water is good for health, drinking more isn't any better.

Water can help a bit in controlling your eating habits, as drinking a glass just before your meal will help you feel full, making easier to stick with a sensibly sized serving.

But the real key to controlling your weight is by managing your calorie intake. Doesn't matter what else you doif you're overeating at the same time.