Sure, this sound reasonable. But you needed scientists to figure out at some point that it's optimal for most people to eat some things, and not other. E.g. you

Sure, this sound reasonable. But you needed scientists to figure out at some point that it's optimal for most people to eat some things, and not other. E.g. you can stay lean eating only fruit, but you'll lack some micronutrients. Also there are some long term longevity effects (or at least people doing studies and claiming such effects). And even with 'noticing' you feel tired, it doesn't always work, at least not for everyone. Obviously most people would feel suboptimal if they start sleeping 4h/day, for example. But anecdotally, I dont notice any subjective difference as long as I slept something like 6.5h+. Sometimes I feel a little sleepy but then it goes away quickly.. sometimes I feel like crap till afternoon even though I slept a lot. And making long term observations is hard because it's hard to compare how tired you're feeling now with how tired you were a week ago.