Why does your body need more water when you are active?

Answer 1

When a person is active, they sweat more, resulting in the loss of fluids. Also, they lose fluids from breathing, because they tend to breathe faster and more deeply. Even a person while at rest loses fluids each time they exhale.

Answer 2

Because when you exercise, you lose a lot of fluids. So what you lose, you have to gain back.

Answer 3

because most of your body is water.