London: Picture the scene. A blonde beauty is jogging along the beach, working hard to ensure her glutes and abs remain as peachily perfect as they were 20 years ago.

She runs past another svelte blonde who is stuffing her face with a packet of crisps. "Oi, what you out jogging for?" says the second to the first, rudely. The first fires back: "So I don't look like you when I get old."

Her friend is speechless for a moment before hurling some crisps at her and shouts: "Why don't you eat some — carbs?"

Sadly, this illuminating exchange between Oscar-winning actress Gwyneth Paltrow and supermodel Kate Moss at Sir Philip Green's recent 60th

birthday bash in Mexico has since been denied by Paltrow's spokesperson and described as a "complete fabrication". Which is a shame, because not only is the reported encounter extremely funny (rowing over the ready-salted), but points up the eternal female dilemma.

No, not to go blonde or brunette, whether to have a career or have children, but which way do you go after 35: Team Moss or Team Paltrow?

There is a salutary moment in any woman's life — the first grey hair; the first time your cheek remains crumpled well after you get out of bed; the first time your hand hovers over the beige control underwear — when ageing stops being something that happened to your mother and starts being something that's happening to you.

How you deal with it defines whether you fall into the Gwynie or Kate camp. Put bluntly — do you rage against the dying of the light with beer for breakfast followed by a cigarette chaser and Glastonbury on speed-dial? Or do you clear your kitchen of all non-macrobiotic ingredients and gulp down a tablespoon of flaxseed oil before settling down for a five-hour yoga session in the hopes of staving off the ravages of time?

Limited choices

In the (pretty recent) past, when women's choices were more limited, neither of these was an option; your 30s were when you raised your children, ran a home, and wondered whether it was time to slip into some Dr Scholl sandals yet.

Today's thirtysomethings who can behave like partying twentysomethings (thanks to delayed marriage and children), or those who devote hours and days to stopping the ageing process, would have been equally alien to our mothers and grandmothers.

"There is enormous pressure on thirtysomething women," says Farrah Storr, editor of Women's Health magazine. "Celebrity culture, scientific advancements and the democratisation of procedures such as Botox means that almost anyone can now try to press the pause button on ageing. Our mother's generation didn't have any of this to deal with."

"This generation of women are just concerned with their looks, not freedom or any of the other things we thought were important — not even men," adds veteran feminist Fay Weldon. "Women have ended up in competition with each other. It's a kind of self-obsession."

Self-obsession or not, there's no denying that Paltrow looks good on her regime. But it takes stunning amounts of self-discipline (something Paltrow has always ‘fessed up to). As the Oscar-winner put it with brutal honesty last year: "The reason that I can be 38 and have two kids and wear a bikini is because I work my [expletive deleted] off. It's not an accident. It's not luck It's killing myself for an hour-and-a-half, five days a week."

And Gwynie doesn't just stick to an Olympian work-out; she is extremely health-conscious when it comes to food.

Despite her newsletter claiming she scoffed French fries at the Vanity Fair Oscars party, she's best known for her strict regimen. She spent a period following a macrobiotics diet; she says she loves fasting and is a fan of a scary three-week detox programme called "Clean" (three weeks!). She even wrote a successful cookery book, My Father's Daughter, which includes such recipes as home-made vegetable sushi. It all sounds rather hard work, so while Gwyneth looks fabulously glowing for her age, you can see why many thirtysomethings look wistfully at Kate Moss's approach. Marriage, motherhood and advertising Mango: nothing seems to have slowed Moss's hedonistic lifestyle. This, after all, is the woman who marked her 34th birthday with an 18-hour drinking session at the Dorchester; allegedly told Lily Allen that the true model diet was "coffee, cigarettes, champagne and vodka"; and who drank beer for breakfast on a post-wedding holiday with Sadie Frost last year.

The problem is that, while Moss looks as luminous as ever on the magazine covers she still regularly graces, there have been a number of pretty unflattering paparazzi shots of the morning after in recent times. And there's the rub. Hangovers and smoking habits catch up with us all.

"After 35 we can no longer pretend to be the ingenue we once were," says consultant psychologist Dr Cecilia d'Felice. "Genes, lifestyle, luck and self-discipline all have their part to play in how well we age." (Or, as Jerry Hall once put it, at some time a woman needs to choose between her face and her figure.)

But Sian To, managing director of the CybHer blogging conference for women (and 39-and-a-half) thinks that most women end up rejecting the extremes that both Paltrow and Moss represent — mainly because there aren't enough hours (or money) for either approach.

"I just don't have time to exercise with four children and blogging," she says. "In my head I'm Gwyneth Paltrow. But on Saturday night, I'm Kate Moss They're both extremes, though. That's why I think women like positive role models like Helen Mirren and Joanna Lumley." And in Weldon's view, neither Moss nor Paltrow are ultimately doing themselves any favours in trying to hold back the years. Whether with partying or with Pilates, they both have to get real.

"It doesn't matter how you express this self-obsession and denying of age — it's only temporary," she says wryly. "They'll both be 50 before they know it."

— The Telegraph Group Limited, London 2012