system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the reason behind the huge weight loss from the G Force during formula races?
gpt
Dehydration. Drivers are coping with high G repeatedly for over an hour, all while wearing multiple layers of fire-retardant clothing, a crash helmet, etc. It can get very warm inside the cockpit, especially in warm weather. So they sweat a lot. 

Drivers have a drink bottle in the car that they sip from through a tube while driving, but it is not enough to keep up with the rate at which they sweat. 

Drivers actually weigh themselves immediately before and after driving, and the difference tells them how much water they need to drink to fully re-hydrate.