Christina Patterson: First, catch your man. But not if you're over 40...

We're mating according to the rules of misogynistic Manhattanites

Everywhere you look in London at the moment, there's a bus telling you that He's Just Not That Into You. The "he" remains unspecified. Not God, presumably, who, according to some posters on buses "probably" doesn't exist and so you should stop worrying and enjoy your life, and according to others probably does and so you should, ditto. Gosh, buses, when they can be bothered to get themselves on the roads, are getting very bossy, aren't they?

Anyway, stop worrying? Who are you kidding? He – your lover, your husband, your boyfriend, the object of your current, or prospective desire, whoever – is Just Not That Into You. As Gok Wan might say, get over it, girlfriend! But Gok Wan is gay. Gok Wan likes big, fat, womanly women. He even likes them naked. But he doesn't fancy them, obviously. And He's Just Not That Into You is a message from red-blooded, straight men to women. It's a message that can pretty much be summed up as this: you'll be lucky, darling. You'll be lucky to kindle some male interest. Don't delude yourself. You ain't so hot. If we like you, we'll let you know.

The line is from a series that became a book that became a film. The series was Sex and the City and the line was from an angst-ridden post-date post-mortem. It swiftly became a mantra and then a no-nonsense dating manual, written by a male "consultant" on the series called Greg and a helpmeet called Liz. "The no-excuses truth to understanding guys" was the subtitle. Shoot from the hip. We'll tell it to you straight. And now it's a film, starring (of course) Jennifer Aniston. Poor, sad, dumped Jennifer, trounced to the altar and motherhood by bigger lips and bigger breasts. Oh, and greater youth. Sorry, we forgot to mention that. If He's Just Not That Into You, it may well be because you're just a little – well, how shall we put this? Mature? Long in the tooth? Old.

A British journalist (a British journalist who, judging by her picture byline has the gift of eternal youth, or something like it) has bravely taken the subject on with a book called How to Meet a Man After Forty. The book draws heavily on her own more-miraculous-than-a-weeping-madonna experience of Meeting a Man After Forty. The man, obviously, was over 40, too. The man had children and had been married before. But the trapping by a middle-aged female of a middle-aged male was deemed such a triumph for womankind that the author, Shane Watson, was apparently mobbed on a visit to her local beauty parlour. Which, by the way, has to be a regular feature of your life if you're going to snare a man. You're going to have to have pedicures, according to Watson. You're going to have to take some care Down There. You might want to consider a Brazilian. And no, she is not talking about the nationality of your prospective man.

You might even have to go a bit further than Down There, according to a book that's created a bit of a stir this week. You can't, it seems, depilate enough. You might want to consider Up There, too. But then you might, according to the book, want to consider all kinds of things you haven't considered before. On the other hand, you might not. You might, after reading Charlotte Roche's novel Wetlands, hope never to think about any of this stuff again. You might think that there is really nothing less erotic in the entire world than an in-depth chronicle of a woman's orifices and secretions. You might also, however, while wincing over the detail, think that the author has a point about entire industries devoted to "feminine hygiene" and the masking of women's natural odours by chemical smells created by men.

You might also, reading Susie Orbach's new book Bodies, feel that women have never been so alienated from their bodies, so distressed by them, so disgusted by them. It was Orbach, of course, who first introduced us to the idea that fat was a feminist issue. Thirty years on, we're all eating ourselves to death, or starving ourselves to death, and we're also hacking at our stomachs, breasts and limbs. In suburban America, a breast enlargement is a popular birthday present for a sweet sixteen. In Brazil, the government funds implants as a treatment for "low self-esteem". In China, women are having their legs broken and extended with steel pins.

We're doing all this because we're never good enough, never thin enough, never young enough. We've learnt to hate our bodies and now we've taught men to hate our bodies, too. Post-feminism (if such a concept exists), we are conducting our mating rituals according to the rules of misogynistic Manhattanites, mating rituals that were culled from small-town 1950s high school America and resurrected to deal with a metropolitan shortage of heterosexual men. It's a sub-prime crisis. It's supply and demand.

But sex, according to all the studies, is all about smell. You can depilate and bleach and coiff and starve yourself into the body of a prepubescent boy, and manipulate and calculate and take the advice of people called Greg, but it seems like an awful lot of trouble for something that will probably happen anyway. Sex is about feeling sexy. Excessive effort is rarely sexy. And if he's Just Not That Into You? Well, more fool him.