Rowan Pelling: 'Penthouse' I rejected. But now I'm ready for you to see me in the buff

Ten years ago I would never have posed for a naked picture. So why now, in the age of Size Zero?

When I was 33 and at the peak of a certain small-scale notoriety as the plummy-voiced female editor of an erotic literary journal, I was amused to receive two unusual, yet identical, requests one rainy Wednesday (though not as outré as the old gent who wanted me to smack him with a hairbrush while singing "Jerusalem").

The editor of GQ, the men's style magazine, and the editor of Penthouse, the rather less stylish men's mag, both wondered if I could be persuaded to disrobe for their readers' pleasure. The editor of GQ promised me a top photographer and great lighting; the editor of Penthouse offered me a wodge of cash. Despite these inducements, I said no.

I didn't have huge problems with the nudity per se. Most claims I had to modesty disappeared long ago and, as a lifelong skinny-dipper who belongs to Cambridgeshire's most venerable naturist swimming club, I'm not too anxious if someone glimpses me in the buff. I had also been photographed in my scanties with my staff to publicise the relaunch of my magazine. Desperate measures for desperate times.

But in this instance I wondered who and what I would be stripping for. I wasn't Jordan, my career didn't depend on it, my husband wasn't mustard-keen on the notion and, having once worked on GQ, I was all too aware of what being photographed by men for male readers of a men's mag involved: generally speaking, hands stuffed down knickers, mouth hanging open as if about to perform a blow-job, and the ever- stylish-legs-akimbo-pose.

I'm not knocking the time-honoured tricks of the trade - very nice too, if you want a quick hand shandy. I just wondered whether I found it interesting or affirmative to join the long queue of women who testify to an already well-proven fact, namely, that any moderately young, slender and comely childless female can be readily made to look like a wet dream.

And then there's the fact that, as anyone who has suffered from an angst-inducing dream where you suddenly find yourself butt-naked in M&S will tell you, nudity is all about context. Of course, for many people there's no more appropriate context for discarding your knickers than the pages of a men's mag, but it seems to me that's mostly true for pop chanteuses, models, starlets and Russian tennis babes.

I had only been asked to strip because in recent years some men's mags, and GQ in particular, have developed a strange appetite for inducing female journalists with posh voices to take their kit off. I suspect this has more to do with male hacks' laddish wagers, as in "Bet we can get that leggy bint at the Torygraph to get her jugs out", than with readers' demands for seeing Nicola Formby or Celia Walden in the altogether. If you have no clue who I'm talking about, my point is already proven.

So why the volte-face? Why bare my all now? I know the conventional reason is to say I'm doing it for breast cancer, abused donkeys, Peta (can someone tell me why small furry animals are saved from a clubbing by the sight of Sadie Frost's bum cheeks?) or the WI.

In actual fact I sat for some naked portraits in the summer of 2005 because, firstly, my talented photographer friend Circe asked me whether I would. Secondly, the request came at a time when I felt my body was evolving from sufficiently explored territories into a more interesting yet treacherous terrain.

Until the age of 35 I'd never been in hospital in my life, but in the previous 18 months I had had a pregnancy terminated after the foetus was diagnosed with a fatal condition, my mother had died of cancer, my son had been born by emergency Caesarean, I'd had a biopsy on my breast, an emergency appendectomy and, following an unexpected collapse, I'd had a cardiogram and been diagnosed with a heart murmur. There's nothing like a brush with mortality to make you embrace your imperfections.

Circe, who is best known for artful erotic portraits of svelte young NY beauties, had decided she wanted to undertake a more subversive photographic project; one that would counteract the cult of size zero waifs and bland, cosmetically-enhanced, digitally-altered female perfection. She told me she was looking for older, larger (magnificently curvaceous in some instances), less conventionally attractive women than her previous subjects.

"Gee, thanks a lot, Circe," I said. She wanted women who had lived a little, or a lot, and who had learnt that tough trick of being comfortable in their own skin. Women with their own specific ideas of sensuality that weren't dictated by the male gaze - a number of Circe's subjects are lesbians.

With two fresh abdominal scars and a post-baby belly to celebrate and my 40th birthday winking at me over the horizon, I found myself challenged by Circe's approach and surprisingly amenable to it. Whereas 10 years ago I might have worried, if snapped naked, that the size and colour of my nipples didn't in some way conform to the accepted norm, now I am just happy to have breasts. So, armed only with a bottle of Sancerre and a Roxy Music CD, I found myself draped over the soft furnishings in my uncle's Pimlico flat while Circe snapped away with an occasional exclamation of, "Oops! I can see your lady bits." As with most examples of age-inappropriate behaviour, it was an incredibly liberating experience.

It seems I'm not alone in finding what would've once been deemed undignified behaviour for a woman past her biological prime curiously invigorating. New research for Woman & Home magazine revealed last week that the majority of middle-aged women shop in stores that are more customarily associated with teenage girls. The survey also showed that one in five women in their forties have a partner who's younger than them, while two-thirds of women over 40 think they look younger than their age. A coinciding Mintel report also talked about the "10 years younger" effect and attributed it, in part, to Madonna and Carol Vorderman - who are apparently leading a charge of well-groomed, middle-aged lovelies who are gloriously, if barely, contained by scraps of Lycra and thigh boots.

If I had read these stats 15 years ago, I wouldn't have believed a word of it. The myopic triumphalism of youth rarely admits to sensual gains to age. It seemed impossible to me from that perspective that the onset of grey hair, crow's feet, drooping breasts and those flabby bits you can clutch great handfuls of on your own back (or is that just me?) could herald greater physical confidence. But it's only by waving goodbye to your totty years you realise there's blessed relief in the fact that advancing years winnow out men who only leched after you because you were young and had breasts.

Yes, you may miss the wolf whistles, but did any woman ever really relish flirting with men who thought the answer to Channel 4's question How to Look Good Naked was quite simply: be 17? Fewer men may flirt with you, but the ones who do are more chivalrous and enquiring. And the friendships you develop with men are more matey, tender and equal, because sexual tension is not so insistent. But it's waving goodbye to youth's tedious, self-loathing insecurities that's so exhilarating.

At 18 I was bulimic, thought myself hideous, and wouldn't have shown my naked body to anyone. At 38 I have three naked portraits by Circe hanging in London's Camera Press Gallery and - forgive me - a nudie pic in a national newspaper. It's not that I think myself especially attractive nowadays. Nor do I think it a dignified, grown-up or modest thing to do. But I no longer give a monkey's. And that's true freedom.

'Bona Fide Women', photographs by Circe, The Camera Press Gallery; 2 November to 1 December