People are really interested in their health. Lots of "hackers" would be super-interested in information that gave them conscious and definite ways to improve themselves.
The problem is that there's very little real information out there.
This study, if were framed properly, would have been at least mildly interesting.
Stomach emptying of fluids depends on the type of fluid... urination frequency too. Thirsty but don't want to pee all the time on a road trip or hacking marathon? Drink milk! Hack your body!
But instead they had to link it with "hydration" which is bollocks. It's not clear that anyone should care at all about hydration unless vigorous exercise or extreme heat is involved because your kidneys do a pretty good job, period.
The problems are that -) human physiology is incredibly complex, and while we are making a lot of progress in understanding all the biological systems, we are far from a point where we can properly model all that goes on.
-) Most people with an actual idea are far too busy doing proper research. They don't care about educating the public that much. And those who do usually want to sell something, in one way or another.
Then solid foods that need to be digested to get out the water would score even higher on this index. Condoms full of water would have an infinite score as the water would never show up in the urine. What I am saying here is that this is a stupid way to measure "hydration".
Speaking of stupid, why does HN have so many of these pointless diet things on the front page?