So I was watching some Tour De France, interesting stats on the cyclists is that with the current heat (30-35°C) they need to go through around 12 liters of water and 8000 calories a day just to have the energy to keep going.
edit: also, they need to consume that for the most part while also cycling up and down mountains as fast as they can, which makes actually digesting anything a brutally difficult task for your body.
And keep in mind that these guys weigh around 130-150lb, they're consuming a fifth or a sixth of their body weight in water alone.
Edited, Jul 19th 2014 2:47pm by Aethien