Exercise changes everything. Sweat is mostly water. If you run for an hour, you can lose a quart (32 ounces). Drink enough to replace it.
Water Consumption Per Day Chart – LFMP
Hot weather? Same deal. Your body dumps water to cool you down. In Death Valley, you can lose 2 liters in an hour just sitting in the shade.
And altitude? At 10,000 feet, you breathe harder and lose moisture with every exhale. Mountaineers often drink 5–6 liters a day. That’s a lot of peeing off a cliff.
The Myth of the 8x8 Rule
Where did the “eight glasses a day” come from? In 1945, the U.S. Food and Nutrition Board said people need about 2.5 liters daily. The media then said “drink eight glasses.”
But the board’s original note? It said most of that comes from food. Oops! The myth was born from a misquote.
Today, experts agree: listen to your body. Drink when thirsty. That’s it. No science degree needed.
