Do you ever learn about health from the media? I do. Here are some things I’ve seen recently. “How to engineer maximum deliciousness, pack in nutrients, increase sustainability, and build crazy food mashups.” But this is rather distant from my goal of eating when hungry. “More than 90% of us don’t get enough potassium.” But enough potassium for what? “Great Sleep Tonight: Pro Secrets, Revealed.” I had not known anyone slept professionally.

One would be more likely to blink at these follies if we were not so surrounded by nonstop fatuities in the imperative voice of advertising. “Tastes so pure you’ll love it.” Does anyone know what purity tastes like? “Discover how good your body was designed to feel.” But who designed my body? “Stress less with the bestselling, multi-award-winning anti-stress drink.” Surely caring about the best, most award-winning supplement beverage is a cause of stress?

Even the bag my fast-food hamburger arrives in won’t shut up. It’s covered with testimony to the franchise-corporation’s caring, its love of me, its love of soil, tomatoes, our planet, friendship, farmers, heritage, my arteries and babies. Yet I can’t even imagine who is caring – what human heart beats inside this paper trash. I think I am supposed to care about these things, and so the salesmen parrot what they suppose would be my aspirations.

Has any free people ever been so shouted at by caring fools and salesmen? Under the guise of useful knowledge, forces that frankly mean us no good, which range in mood between hysterical enthusiasm, indifference and careless exploitation, warn us with “health” advice that is variously incoherent, short-sighted (to be reversed or falsified five years later) and banal. You can tell people not to eat eggs, but a decade later you’ll be telling people to eat eggs. It seems trivial, but it always costs something – in worry and stupefaction, and in hours of our lives.

You could say that this advice all comes in bad faith. But the voices which approach us in good faith may be even more to blame.

Health, exercise, food, sex have become central preoccupations of our time. We preserve the living corpse in an optimal state, not so we may do something with it, but for the feeling of optimisation. More and more of life gets turned over to life maintenance at the very moment you’d think we’d be free to pursue something else.

I find it hard not to want to live longer. I also want to live without pain. This means I want health. But when I place myself at a point within the vast constellation of health knowledge and health behaviours, I can’t help but detect some misunderstanding. The systems of health have little to do with my simple ambitions. There is something too much, or too many, in them; too arbitrary, or too controlling; too doom-laden, too managerial, too messianic.

We should spare a thought for the fate of what used to be called the “necessities of life”. Necessity dictates what must be done for the body before anything can be done for the mind. For millennia, people have known what the necessities of life are. Food, shelter and clothes, made or won by labour. Sex and reproduction, tied to the labour of childbirth and work of child rearing. Sleep. (Alexander the Great said that sleep and sexual intercourse, more than anything else, reminded him that he was mortal). Movement, as has only come into focus since we began to sit for so much of our days. Touch, perhaps, as has become more obvious as the world became less tactile and rough, more screened and smoothed. Excretion.

But 3,000 years of civilisation have worked to make these necessities easy to come by. In the last three centuries, human progress has pacified necessity in the rich countries. Back-breaking labour has been reduced. Food is inexpensive and superabundant. Sexual desire has been decoupled from pregnancy. The dangers of infection, fever and accident have been diminished by medicine, and medical research seeks ways to head off more slow-growing diseases. For many, simply to be born in a rich nation is to have won the lottery for inexpensive access to the necessities of life; to be gloriously, unprecedentedly free from cares historically and in comparison to much of the globe. There is freedom to enjoy – and there are wealth and material freedom to spread to others. For progressive civilisation had always expected that meeting necessity in the west was a mere prerequisite to further, higher goals: justice, equality, democracy, and the extension of ease of access to the necessities of life to all.

But we have taken an unexpected detour on the way to meeting those higher goals. Once progress had made it easy to acquire the necessities of life, other forces set about making those needs mentally complicated and hard. Into this category goes much of what passes for wisdom about health, exercise, food and sex. Inexpensive things have become expensive, trivial matters require obsessive thought, universal biology is mazed with fashion and status-seeking, and free possessions are commoditised. If I feel sure of one thing, it is that this kind of “health” imperative is not moral. It is grooming – what monkeys do in picking nits out of their fur. We may find that grooming sits among the subordinate necessities of life. But surely the ceaseless grooming and optimisation of everyday life stands in the way of finding out how else we could spend our attention and our energy.

A decade ago I wrote an essay titled “Against Exercise”. It came about from a trip to the gym to run on a treadmill. I was standing in the usual stance of mutual disregard, pretending not to notice my neighbours sweating through skintight pyjamas and making their angry – or, I suppose, fierce – faces. I tried not to look up when someone grunted or shouted, and kept my eyes politely on the calories ticking by on my readout, just as in a lift I’d keep my eyes on the floor numbers.

But then I breached convention and looked around, and was struck down by the sort of vision that must have come to William Blake, a glance into heaven and hell, suddenly manifest in his garden in Felpham. There was a young man crucified on a lat pull-down. There was a young woman whose legs were madly turned by a spinning bike. No one looked happy: they either looked like executioners, grim as death, or victims. Certainly no one looked sociable – though this might be the space with the most people, together, supposedly at ease and enjoying leisure time, that they would enter all day. I turned from one unseeing face to the next, each chasing some number, and I said: “You are condemned. You are condemned. You are condemned.” I, too, was condemned. I got down from the treadmill.

This, of course, had nothing to do with an intelligible argument. So when I got home, I began to try to figure out why we go to the gym. There are explicit rationales, and the precise words and phrases which recur in official injunctions to exercise. Then there are the quiet things people say in passing, about the pleasures and the ghastlinesses of it all. Modern exercise has a background in sport, even in the ancient gymnasia – but it is really quite different. It certainly seemed striking that, as advanced societies have done away with much industrial labour, and have automobilised transport, the new immaterial labourer spends his leisure mimicking the old repetitive gestures of the die press, or a stevedore’s lifting of cargo, or a rural traveller’s walk to a distant town, but turned into spectacle, sped-up, numbered, and producing muscles that serve no practical use but more of the same mimicry. And that this is so often experienced as obligation, rather than play.Then, I began to read and write about diet and food. Certainly we are in a golden intellectual age of political critiques of industrial food production. The pollution and cruelty of factory farms have come into public view. The dangers of pesticides and groundwater contamination lie behind the progress of organic farming. But alongside the public-spirited motives for a return to heirloom products, artisanal production and farm-to-table eating, there seems to be another push towards rarity, social distinction and hostility to the cheap mass provision of food as a fundamental civilised achievement.

Most ambiguous, to me, is the new figure of the foodie. Only in a culture cut off from agriculture and need can food become a hobby and grounds for individual identity. The old gourmet was a bit of a snob: he wed himself to France or Italy, learned to cook a single cuisine and became obsessed with importing, usually wine and cheese.

The foodie differs in having the whole globe at his fingertips. His cookbooks gravitate first to Europe (Provence; southern Italy), then quickly carry him to Turkey, Morocco, Vietnam, India. No single tradition exists for him to learn, no singular importers to patronise. Rather, an ocean of ingredients washes up on his shores. There is no food we can’t access. There is no traditional food, moreover, that can’t be further enchanted by our concentration, restriction, choice, and discrimination between better and worse specimens. Would you like some chipotle with your lemongrass? We add the value of our intellectual labour, our “finishing” of the world’s raw materials.

The foodie wades out and swims in possibility. And then, surprisingly, many a foodie will deliberately restrict his range. He sets rules or laws for himself that make the quest for food harder and the thinking more complex. Undiscovered foods only; “authentic” restaurants only, or kitsch diners or barbecue joints; organic food only; local or farmers’ market food, raw food or slow food only. Foodieism is a natural hobby for first-world professionals, ostensibly showing an interest in the world, but referring back to domination and the perfection of the enriched, physical self.

Having our food supply made simple, we devote ourselves to looking for ways to make it difficult. Another route is through dieting, ostensibly for health. Here, though, the weight-loss imperative, with its shadows of attractiveness and social distinction, and other fantasies of rarity, difficulty and expense, complicate the fairly mundane research consensus on improving health: eat moderately, move more. You can avoid bread, eat only protein and fat, and lose weight – since too much weight is said to be a killer. But as you polish off your bacon, steak and cheese, nothing has falsified the old research that correlates animal fats with plaque-filled arteries, heart disease, stroke and cancers.

You can rediscover your inner ape and revert to a “Paleolithic diet” with evolutionary justifications. But no 21st-century butcher can provide you the animals eaten by our Paleolithic ancestors. You will not eat it in the conditions of scarcity of our Paleolithic ancestors. None of the rest of your life, upbringing, habits or ingested substances resemble those of our Paleolithic ancestors. You might equally ground your fantasies of historical destiny in the fact that the entire history of human culture and civilisation has occurred in the Neolithic era – ie, facilitated by the planting of grain and domestication of animals. Star Trek fans would seem to have a better grasp of the scientific method.

Then sex and sexuality began to interest me. We’ve had a remarkable sexual liberation – particularly since the 1960s. Major achievements have included the end of shame and illegality in sex outside of marriage, the feminist reorganisation of intercourse around the female orgasm as well as the male; the destigmatisation of homosexuality, and a new fluidity to the norms of gender identity. The underlying impetus in all these reforms was to remove social penalties for doing what people were doing anyway.

But competing with true liberation has been sexual liberalisation – an effort to tell you that only expertise, exposure, advice and apparatus can let you enjoy, in the right way, what was already freely possessed by you. A true test of liberation, as distinct from liberalisation, is whether you have also been freed to be free from sex. To ignore it, or to be asexual, without consequent social opprobrium or imputation of deficiency. We ought to see social categories of asexuals, who are free to have no sex just as others are free to have endless spectacular sex, and not feel towards them either suspicion or pity. One of the cruel betrayals of sexual liberation is the illusion that a person can be free only if he holds sex as all-important and exposes it endlessly to others – providing it, proving it, enjoying it.

I think sometimes of a John Prine song: “We are living in the future, I’ll tell you how I know / I read it in the paper, 15 years ago.” We often speak about a coming age. In that near future, we’ll enjoy heavenly ease and wellbeing, safety and leisure. How wonderful it will be! In fact, I think we ought to admit that many of us in the rich nations are already living in that future, and have been for some decades.

But our surprising response to our times has been the creation of new forms of pseudonecessity. We go to the gym to strain at imitations of hard labour, lifting nonexistent roofbeams, hoeing nonexistent fields. We pretend that our food – now safe, plentiful, cheap, delicious – matters so much to our bodies that we must perfect it, elaborating a new necessity of pollution and taboo for heritage grains and laborious artisanal manufacture. We refuse to recognise that an 80-year lifespan of activities and projects is functional immortality for the human animal. Or that dying is necessary, just to let new people come on to the earth. So we substitute life-preservation for living, spending invaluable portions of youth and middle age on trying to increase our odds for an extra one, two or five years at the very end.

Frankly, I suspect that an ethics of living in a rich nation at the dawn of the 21st century involves not caring so much about your health, your diet, your exercise and your thrills. The meaningful time is now. We should be prepared to enjoy our good luck, and drop dead after a sufficient length of time – but ask, along the way, what we actually wish to do with our time. A culture of health and futurity, right now, represents a terrified or intimidated flight from moral freedom – covering our eyes from the fact that we have no further urgent tasks of bodily improvement, and really need to choose between setting new social goals, or just grooming ourselves into eternity.

• Against Everything by Mark Greif, published by Verso, is available for £13.93 (RRP £16.99) from bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99. Mark Greif’s UK tour starts on 3rd October.