But my bum does look big in these

Levi's have spent millions repackaging 501 jeans. But Clare Dwyer Hogg finds the perfect anti-fit comes up a little short

I know adverts are there to tell you what you want. I know they don't encourage independent thought, and I know this is especially true for the ones which tell you that you should think independently. But I like the Levi's ad for "anti-fit" 501s. "Be an individual, and go against the norm", it seems to be saying. "Wear baggy jeans to prove it." And even though, deep down, I know that it's already the norm to wear baggy jeans, I just know Levi's are telling me something new.

This is obviously good advertising, because, before I saw the ads, I knew that Levi 501s weren't cool. I knew that without anyone telling me. I am therefore, it seems, exactly the sort of young person who has contributed to the steady decline of 501 sales since the nineties. And I'm exactly the target audience for this radical new model.

The marketing people at Levi's pitched it perfectly: after two viewings of their ad campaign, I knew that anti-fit jeans - baggier than old 501s and worn lower - were The New Thing, but not too try-hard. I knew that they were laid back, and a bit free-wheeling. I knew, even though I'd never admit it, that if I had a pair, I'd look understated but very cool, and probably urban and street and cutting edge and individual and fun... and then I tried some on. And that's where the dream ended.

Because, in real life, these jeans aren't meant for a woman. Writing these words sorely disappoints me, because I have no axe to grind with Levi's. I sincerely want the jeans to work. I love the engineered ones. But these 501s only work if the effect you are aiming for is hip enhancement. Big hips, big legs, narrowish ankles. I tried them on in the office, and people laughed at me. Outright. They said cruel things, like "unflattering" and "they give you big thighs". Very big thighs. My vision street credibility was fast gone pear-shaped.

So why did one of the world's most famous brands get revamped? In order to find out you would have to rewind to the late 1980s, and a certain television advertisement campaign in which Nick Kamen stripped down to his undies in a laundrette. Almost overnight, the straight-legged, slightly-tapered at the ankle, slightly high-waisted denim trouser became the ultimate in chic. Sales sky-rocketed by 800 per cent, and no boy band worth their turn-ups was seen without them. The 501 was a sartorial essential among prepsters, punksters and American pensioners alike. And there began the end of the affair. The boy bands became men and started wearing the jeans with shirts instead of T-shirts. Worse, they started tucking the shirts in, and wearing comfortable shoes. 501s became a required dress code at dress-down-Fridays. Put it this way: it wasn't a good look.

Levi's have sought to make the jeans less Jeremy Clarkson (who hasn't realised his jean-wearing is an exemplar of fashion death) and more symbolic of a time in keeping with the anarchist 1960s, when the jeans were hip.

"They have had to attempt to make people think 501s are new and changed without explicitly saying that," says Dave Burrows, who works at Flamingo International, the company who researches the Levi's advertising campaigns. "It was a very tricky thing. People thought they knew exactly what 501 was, and nobody wanted to wear it anymore because the old 501 had been completely discredited."

Levi's have therefore had to excite people about the differences in the products, without sticking a knife in the heart of the jeans that made them a fortune. "I think the strategy has worked very well," says Burrows by way of a verdict. "It took an awful long time to hone that advertising."

And an awful lot of money. The company have spent an estimated £10m on the redesign, and the adverts are the first for the 501 brand in seven years.

The resulting campaign - in which two people discuss, in a language which approximates to Spanish (but isn't), how essential it is to have baggy jeans - is aimed squarely at the "now" generation. The square guy in tight trousers rips his pocket when he tries to put his hand in it. The other spends a long time explaining to a bouncer outside a smart club why he shouldn't be allowed in wearing his anti-fits. A great concept appeal, for sure. But, try on a pair of anti-fits and you will quickly discover that the concept appeal - which is unisex - doesn't quite translate. In other words: anti-fit jeans look terrible on women.

"Levi's have not been good at women's products, and they've known it, for years" Burrows says. "Women simply don't find 501s a very stylish product. So Levi's have moved away from style - the campaign says Levi's cut through fashion. Women won't buy that because they want to look good in them, physically as well as attitudinally."

So there it stands. Frankly, I'm a little offended. Is he saying that women are shallower than men? That men are more comfortable with a cool attitude - that they can "cut through fashion" - but that women stop at appearances?

I bought into the concept, but when the jeans made me look fat, I bowed out. Is that the makings of a hypocrite? No, I just like to wear jeans that suit me, as opposed to ones which bag and cling and taper in the wrong places. Wearing them a bit bigger doesn't look good. And wearing the right size is just too high-waisted (yes, the fashion label Chloe may be introducing high-waisted trousers this season, but the whole point of anti-fit is that they're supposed to be casual).

Men have a different body shape to women, and clearly the 501 suits a man. They originated, after all, as the working man's jean - sturdy, capable, untailored. I get my colleague Mark to try a pair and, truth be told, they look great on him. But can something really "cut through fashion" if it is actually fashionable? Men can have a cool attitude, and look good in these jeans, so that doesn't count. Hell, I'd still be wearing the jeans if they did both for me. Men can mooch in them, women cannot. End of story.

Perhaps this observation is borne out in the fact that, as far as I can see, the men look good in jeans throughout all of the new Levi's adverts. However, the only woman on view is seen so close to the camera that her legs are actually cut off. Just her top and waist are visible. That's all. Probably coincidence, but maybe not.