Mark Edmundson:

Health should manifest itself as a means to an end. We want to be healthy so we can get something practical done—or better still, something divine, something celestial. But now, since we do not know what we are doing here, do not know what we want or need, health has become an end in itself. People pursue health for its own sake. Why do you want to live? we ask the compulsive exerciser. The answer is not So that I can finish the work; so that I can make the discovery; so that I can find enduring love. The answer now—implicit, but to me, alas, unmistakable—is that I want to live simply to go on living. With the disappearance of tenable ideals, life, simple life, has become the great goal.
…All of the energy that once went into the pursuit of the ideal is now dormant, for almost no one can believe in ideals anymore. A quest for artistic perfection? Absurd. A search for true and absolute knowledge? A joke. A life’s dedication to compassion and lovingkindness? You must be kidding. So what is to be done with the power of human will that might once have sought after these things? It is redirected to more quotidian business. People now pursue a means—staying alive—as though it were an end in itself. Epic measures of energy invest a rank banality, for in truth there is no sustaining meaning to be had, no triumph to be achieved, simply in the maintenance of biological life.
I agree that the effort to simply prolong existence has become a raison d’être for many people, but I think he’s overlooking how fanatical health regimens provide one of the few socially acceptable opportunities for condescending, judgmental moralizing, at least among the class of people who have the time and leisure to carefully tailor their diet and exercise for maximum benefit. Not to mention how it allows for the reappearance of that good old Protestant work ethic, and the accompanying smug pride in knowing you’re one of the saved, the elect. The temple might be biological these days, but priests will always be with us in some form, it appears.