“Nowadays the 'drink eight glasses of water a day' is not considered sensible,” said Stuart Galloway, an associate professor in physiology, exercise, and nutrition at the University of Stirling, back in 2020. “As humans, we have this homeostatic system, so when we need water, we feel thirsty.” Drinking when you are thirsty, he said, maintains your body’s water level within about 1-2% of its ideal state. “For most people, this is absolutely fine. Even for athletes, a loss of around 1% is considered to have a negligible impact on performance. So, although thirst may not kick in until you have lost some body water, this is not necessarily a bad thing.”⁠ ⁠ As we get older, our sense of thirst can get fuzzier, and that is when dehydration can become a threat. It is a similar story for children, too. So perhaps the advice to drink water before you feel thirsty was originally aimed at parents and the elderly, but now healthy adults are putting away gallons of water in a quest to be their best...