What I think is true of 'healthy lifestyle' is that it's Not something that you have to prepare or make an item in 'to do list' it's what we mostly predisposed toward. Even toddlers would spit out something that tastes or smells bad, often a sign it's not good for you. Sure as we grow we learn more about specifics but I have never known a baby who needed a pediatrician to teach how to stand! And soon the little one is running and climbing and jumping and Inventing games to play. as Brian Pronger, author of Body Fascism, says that in today's world: The impetus to move comes not from the infinity that the body is but from the finitude that it is not.
But that's just the physical aspect of our healthful development. As newborns, we find life immensely attractive so we poke, and drop and smash and touch even taste and try to eat, soon learning what is edible and what's not. So, Rachel, I think nature has done a pretty darn good job of keeping us on track that leads to healthy lifestyle. We may sometimes forget or ignore even believe in misinformation (and placebos) but if we also have others to test our assumptions we end up not too far from what is good for our bodies and psyches.