This is largely effected by the nutrition / mental / health state of the individual. I personally spend a lot of time (cooking, sports, spend time researching mineral/vitamin/other supplements), and it took me around 4 years to find the things my body needs. I am now very rarely "energy exhausted" and mentally clear the whole day, having more energy than 10 years ago.
The message here is that one can spend time and pick up habits that make the body function better, with a good chance that the efforts will pay off one day.
Ah well, being fit certainly helps, and I'm pleased you found what works for you! But so does being early twenties instead of in your forties (not assuming anything here, just stating age is one of many factors). If only aging could be solved by taking a multivitamin :)
And while I agree that taking care of one self is important, I want to touch upon a more fundamental point. I am perfectly OK with taking rest from time to time, or taking it easy, or just sitting back with my feet up enjoying a good book, or a glass of wine with my wife.
There's in my opinion little need to always be on 100% and it's perfectly OK if people aren't.
I know this opinion is like cursing in church on this forum, but many people would do well being nice to themselves a little more.
I think the point of this calculator is to show people that there's time to take those breaks. I filled it in and over-estimated a bunch of areas and it still said I have 11 hours of free time each week. That's a whole lot of books and wine that I can enjoy and still meet all of my existing priorities including spending time with my kid.
That's freeing in a way, it tells me that when I feel pressed for time it's really all in my head and taking an hour to read a book shouldn't be a problem if I just take a few minutes and prioritize my time.
Also it's probably useful for some people to see how much time is spent on work and commuting relative to other parts of their life. If they truly have no time to read a book but work+commute is eating up more than 50% of their days, maybe it's time to do something about that and fix one or both parts of that equation (move closer to work or change jobs to get closer to home, and work fewer hours)?
Then there is (on top of above) the vitamins / minerals category, in which I was shocked to find that most supplements out there are in a form that doesn't get used by the body. Sorry, no english doc here :(
Addressing my various food intolerances - it's very personal and it's more about the process. Experimenting with avoiding gluten, milk, egg (for me). Try-and-repeat. Be consistent (this was the hardest for me).
And fighting my constant virus load - again, very personal, but these ones that work for me, using in combination: lactoferrin, grapefruit seed extract, ganoderma lucidum mushroom, propolis drops, and one I won't write down on HN because I get downvoted for it... :)
