Good health is always relative.
We each come into the world with a genetic and karmic loading which means that our health will always be limited the optimum for ourselves as individuals.
That said, a diet of Big Macs is probably best avoided by those without the siddhis to deal with that...
But I believe that the most important aspect of a healthy life is our mindset.
I am quite literally old enough to be the grandfather of many members of the forum.
I am as we Brits say , in good nick. I seldom bother my physician apart from being better than him at golf..
And I am completely convinced of one thing. The state of mind we are in when we eat is more important than what we eat.
A meal of lean meat or fish a few carbs and veg, eaten with gratitude and a peaceful mind is far more nutritious and healthy than a meal of tofu eaten in fear and aversion and contempt for humanity.
It is the latter that constricts the arteries and fuels a hormone response which sets up conditions for cells to mutate into degenerative conditions.
Of course a meal of tofu eaten in a state of goodwill and equanimity may be the best option of all....
But as in all other aspects of what arises for us, mind is chief.