You are a man. You stand naked, looking down. What do you see? Is it (a) a set of wedding tackle and your feet? Or (b) a looming, bulbous vista of unsupported flesh that you can hide a finger in if you poke hard enough, and quivers when you cough like some huge hairy blancmange?
If the answer is (a) you may go out into the world feeling insufferably smug (though remember, please, to put your clothes back on first). But if it's even approaching option (b) you are in trouble. Your only consolation is that you're not alone. Far from it. Last week, the results of a survey by Professor Stephen Gray of Nottingham Trent University exposed the sorry story of modern man's tummy. It is a tale of sag and spread, but also of self-loathing and its regular companion, self-delusion. Of 2,000 men investigated by the professor, half were discovered to be squeezing into trousers too small for their waists in desperate attempts to convince themselves that they weren't really swelling up round the middle.
Tight trousers have become the tailoring equivalent of the comb-over. But the tape measure does not lie. Thirty-eight inches is now the circumference of the average male mid section, compared with 36in only 20 years ago - more than a yard of lard and rising. Six years ago, 13.8% of British men were classified as obese, and that figure has risen to 17.3%. Men are getting fatter and the consequences are already dire. For one thing, they are miserable about it: more than a third of the survey sample said that they disliked their stomachs more than any other part of their bodies.
Yet although nearly half defined themselves as either slightly or very overweight, only one in five said they were worried about it, and when 10 volunteers were shown 3D images of their own frontal profiles, only four recognised them. The reason is heart-rendingly plain; when he stands before the mirror, Mr Average pulls back his shoulders and holds everything in; the rest of the time he simply slumps and subsides. Oh dear, oh dear, oh dear.
Then there are the knock-on effects. As well as the familiar costs to the heart and blood pressure of being overweight, experts on obesity reported last month on a link between waist measurement and susceptibility to diabetes. Men with 37in waists are thought to be 10 times more likely than thinner ones to contract the disease, and many of those who do also go on to suffer from heart disease, kidney complaints or blindness. And as for those exercises in wishful thinking that go on when men are alone with a selection of trousers in the changing booth, these do nothing for the appearance and less for the contents of the scrotum: crushed nuts may be fine on ice cream, but can wreak havoc on the sperm count.
These latest of many warnings to men about the damage caused by lack of exercise and too many bags of chips coincide with the escalation of the male health and vanity industries. So is rising concern about male tubbiness entirely justified on health grounds, or is it partly provoked by the sort of obsession that drives so many women to take up dangerous - and pointless - diet regimes or becoming chronic work-out bores?
On the one hand, concern about the poor diet of many men and their ballooning bulk seems justified on health grounds. As well as noting with alarm the swift expansion of men's girths, health professionals have begun placing more emphasis on stomach size as a predictor of future problems and less on fat collected around bottoms and hips.
For obvious reasons, women have welcomed this rehabilitation of the pear shape. But it is bad news for those built like Granny Smiths, who are more likely to be men - news that men would be wise not to ignore. However, attitudes have hardened towards the male midriff for social reasons, too. Twenty years ago, the beginnings of a pot belly in a young man was a source of pride among the drinking classes - as proof that they were drinking lots of beer. But now the six-pack reigns as visible proof of virility and male physical beauty.
Fetishism of the belly among men is not new. It, and the plumbing it contains, have long provided key metaphors for the masculine ideal: real men are meant to have "guts", have the "stomach for a fight" and should never be "yellow-bellied".
To this has been added a new standard for male attractiveness, fuelled by the vociferous demands for post-industrial "softer" masculinities and the conspicuous "gaying" of the men's fashion trade.
The washboard belly signifies beauty as well as brawn, vulnerability as well as "hardness" and, in case we forget, it is located within breathing distance of the penis.
No doubt the proper attitude to take towards all this is the same one urged - albeit with limited success - upon young women and girls about their shapes and sizes: broadly, that the human male comes in many different forms and that a balance should be struck between taking care of your body and making yourself miserable because it fails to resemble David Beckham's or Jude Law's. In The Full Monty, remember, the character called Dave, played by Mark Addy, ended up completely demoralised by a combination of joblessness and paunchiness. But his wife still fancied him and his spirit was liberated along with his gut when, at the end, he boldly bared all.
Yes, quality of life is a complex, subjective business. But who seriously doubts that the sum of human happiness would be massively increased if, when men rolled off the sofa, their toes touched the carpet before their navels?