I'VE never done it before, but I'm going to do it now. I know I shouldn't and I feel bad about it, but when people ask how old I am, I can't possibly say the word "forty".

Thirty was bad enough, but I could take that. After all 30-somethings are young. They're hip, they're fun, they're popular. I mean who doesn't love the television series Cold Feet? And look at the success of the dramas Big Bad World and This Life.

Of course, many women start families in their thirties - I was 35 - but they can also enjoy the single life and date men without that awful 'left on the shelf' feeling hanging over them. They can still get away with shopping in Miss Selfridge - although I have begun to feel more conspicuous with the passing years.

Thirty-somethings can't change career as easily as a 20-something, but there is growing evidence that, in a few years' time, they will be able to flit from job to job as effortlessly as a cabinet minister.

Yet move on a decade and it's a different story. How many TV programmes feature the zany lives of a 40-something crowd (Frasier is the only watchable exception)?

Your biological clock needs batteries and if you are free and single you spoil dates by clumsily lying about your age. You take pains to keep your passport and driving licence under lock and key, and worry like crazy on your birthday in case someone sends you a birth date copy of the Times.

Unless you've got a teenager with you (you can always grab one on the way in) browsing in Miss Selfridge is out. For 40-somethings, all roads lead to Evans or Bon Marche.

And you spend your life fending off those women who sail up to you in the street, to show you how easy it is to buy pastel-coloured separates by mail order.

Put your date of birth on an application form and you just know it will do you no favours in the jobs market. It's just so middle-aged which to your average employer brings with it terms like 'staid' and 'set in their ways'.

I've always been slightly irritated by women of a certain age who maintain the right to silence when asked their age, or become horror-struck as if they've been told to remove their underwear. But now I'm in full sympathy. I'm sticking to 1961 as my DOB, and that's that.

Well, so long as I look the part. I won't profess to be 39 when I'm 70, with a permanent stoop, bow legs and skin like an avocado.

Not that I'm 40 yet. That much-dreaded day of reckoning is yet to come. Suffice to say, that when I next write this column I'll be... I can barely write it, let alone say it.

I know that my 40-something friends will be disappointed by my attitude. "It's great, go for it!" said one.

"Treat yourself to some lovely, sexy underwear and revel in the fact that this is where life begins," said another.

But I don't see it like that. I don't feel 40. I don't think I look 40 - and the bottom-line is, I don't want to be 40.

So no birthday cards, please. The way I feel, the most appropriate message is 'With Sympathy'.

Lose weight by watching TV, lose weight by lying down, lose weight by rolling your eyes. Now there's a new plan to slim down by breathing.

If there's money to be made in all this - and I suspect there is - I feel obliged to point out that there's a lot more weight to be lost by not breathing.

It must only be a matter of time before that one hits the glossies. Well, you read it here first.