So there you are in Pret, your hand hovering over an Italian Prosciutto Artisan Baguette (which, I have to admit, is my favourite), and your eye is caught by a little label. 636 calories. You hesitate. Should you instead opt for half a crayfish sandwich (185 calories)? Or a tuna salad (120 calories)? Hungry and confused, you dither, defeated.
Or maybe you're in Subway, which has now taken over McDonald's as the biggest fast food chain in the world. Calorie information is on the glass counter as you make your choice. A six-inch meatball marinara (my son's favourite) is 511 calories. Or go low fat with a 'Veggie Delite' (202 calories). Or maybe you're in Boots. Here you've struck gold. Whole cabinets full of cold, calorie-counted sandwiches. I hate it. I hate it. All I wanted to do was buy lunch, and instead I'm wrestling with a mental maths challenge. Question one: 'If the average woman is supposed to eat 2,000 calories a day and she's already had a bowl of porridge and two cups of tea, how many calories can she eat at midday and still have enough left over to eat supper at 8.30pm?' All that calculation is bad enough.
But this obsession with calories takes the joy out of eating. It's a bit like having sex with an instruction manual by your side. Mention the word calories, and most women will find a sliding door in their brain whacking open to reveal a huge databank of guilt - half-remembered magazine articles, miserable equations (one slice of toast equal two apples), and memories of hopeless diets. We're skating round a world of lettuce leaves. We're flirting with ideas that make most of us bloody miserable - you can't be too rich or too thin, nothing tastes as good as skinny feels. For a lot of women, the word 'calorie' - so slim, so virtuous - is fat with meaning.
You could argue, in any case - especially with all we now know about yo-yo dieting - that counting calories isn't the best way to keep to a healthy weight. In his lovely book In Defence of Food (Penguin, £9.99), Michael Pollen argues against all the confusion that's been built up by the food industry, nutritional scientists and (oh dear) journalists and says the simple answer to the supposedly incredibly complicated question of how to eat healthily is: Eat food. Not too much. Mostly plants. But the current government says that we have to be realistic.
British people eat lots of ready-made meals, so we have to try and help them make the best decisions. The secretary of state for health Andrew Lansley - the man who hopes to revolutionise the NHS - wants restaurants, takeaways and fast food outlets to provide information about the calories contained in the food they offer. (Even though a similar initiative by the Food Standards Agency a couple of years ago fizzled out rather ingloriously. Most of the food chains gave up on the idea, leaving only a few, like Pret, to fly the flag.) 'In ways like this,' says the Department of Health press office, "people can be empowered to make healthier choices through the provision of information." Can they? I'm not so sure.
Larger fast-food chains in New York have had to display information about calories since 2008. But a recent study, published in the International Journal of Obesity, found that while 57 took the information into account when they ordered. Nearly three-quarters of them said that the most important factor affecting their choice was taste. Admittedly, these were teenagers - and teenagers are often so ravenously hungry they'd probably eat Andrew Lansley himself if he came with a tasty barbecue sauce. But labelling food with calorie content seems pretty pointless if the next generation chooses to ignore it.
Subway is currently conducting research in 50 of its stores to try and pinpoint how and where its customers would like calorie information displayed. It's keen to emphasise its commitment to healthy eating - its website www.subway.co.uk makes a point of telling you about the American college student Jared Fogle who lost 17½ stone by eating nothing but Subway sandwiches for a year. So maybe I should ask them to take a few points into consideration. These are: 1) most women don't want to stand in a lunch queue practising their maths skills; 2) a lot of women can't concentrate at 4.30pm because they've intimidated themselves into buying the kind of low-calorie lunch that would satisfy only a dieting gnat; 3) it is a truth universally acknowledged that you can stuff yourself silly on fresh raw vegetables, stay a healthy weight and never have to know the calorific value of any of them; and 4) it is probably not a good idea for anyone - man, woman or child - to buy a foot-long sandwich full of melted cheese.
And please, Pret A Manger, when you see me coming, would you hide all the calorie information about your Italian Prosciutto Artisan Baguette?