This is what William Hazlitt (1778-1830), one of England’s greatest essayists, had to say on growing older: “When grace is joined with wrinkles, it is adorable. There is unspeakable dawn in happy old age.”

This is Catherine Deneuve, presumably when she was all of 25: “A 30-year-old woman must choose between her bottom and her face.”

And here is that well-known sage, Rachel Hunter: “I’d choose my face within two seconds.” Hunter went on to single out Teri Hatcher as one who has clearly chosen backside over beauty – a decision that Hunter sorrowfully concluded was at the very least unwise and regrettable, and possibly morally defective to boot.

As beauty philosophies go, one can’t help feeling that Deneuve and Hunter’s bottom v face equation falls slightly short in terms of philosophical depth, kindness and understanding. And yet, just as we cannot help deploring such simplistic, not to say shallow, judgments, one also cannot help scrutinising the latest pictures of Renée Zellweger and thinking blimey, there’s someone who’s definitely chosen her bottom.

Indeed, honesty compels me to confess that, during that past four weeks of shows, I have spent the odd minute or 20 perusing the faces and contiguous areas of colleagues as we await the unspeakable dawn of another fashion show. The findings are not always what you might expect. For while the celebrities in the front rows have often reached what the French used to call un certain agebut which is now more accurately described as ageless, the women who work in fashion tend to be more wrinkle-friendly than one might think. For the inner sanctum fashionistas – the top international editors, stylists and buyers – being thin has always been more important than having a dewily youthful complexion. It’s true that (subtle shots of) Botox have made inroads, but facelifts are relatively rare and make-up is always sparingly applied – or at least made to look as though it is sparing.

Perhaps this isn’t that surprising. Prioritising a slender body over a youthful face is simply pragmatic in a business where looking chic and the ability to pull off the latest fashions – invariably requiring neat proportions – are important. As far as the fashion industry is concerned, stylishness is youthfulness. This is not the normal world, where homo sapiens are genetically programmed to find a partner, where males traditionally attract through power and females attract through their ability to bear progeny (ie, look young). In the fashion world, a skinny 60-year-old who can carry Lanvin or Prada gracefully and doesn’t have to confine herself merely to wearing the handbag because she can’t fit into any of the (diminutive) sizes has as much cachet as a slightly plump, clueless 20-year-old, if not more.

Away from planet fashion, and back in the real world, it would be nice to think that by the time one reaches the age where one has to think about such choices, one is emotionally way above them. But the truth is that, while we would probably all like to be as one with Hazlitt on this, and just let nature, wrinkles and major hair-loss take their adorably merry toll, you’d have to be exceedingly high-minded not to concede that Deneuve is on to something, though possibly not quite what she thought she was on to all those years ago when she first raised the subject. Perhaps there does come a moment in a woman’s life – and a man’s too, although the physiological details are slightly different – when she needs to take a long, hard look in the digital database of recent beach snapshots and decide whether maintaining a girlish slimness isn’t being achieved at the expense of something else. The bit about having to choose between your face and your body at 30 is way off beam, however. If 60 is the new 40, as one magazine coverline optimistically suggested recently, then 30 is about 10.

While life can offer us a number of “sitting beauties”, ie, women such as Nigella, Oprah (intermittently) and Judi Dench, who have clearly decided to pamper their faces and let their bodies get on with it, Hollywood is inevitably a-twinkle with women who are in their forties and fifties and apparently having it all, anatomically speaking: Demi Moore, Michelle Pfeiffer, Halle Berry, Diane Keaton, Julianne Moore – ageless, slender paragons all of them, with nary a sad, haggard little face between them, which is at it should be, given the advances in cosmoceutical and cosmetic sciences. In fact, given all the vitamin, Botox, hyaluronic, Surgiderm and Restylane injections available, not to mention an exciting sounding newcomer called carboxytherapy which helps to stimulate muscles supporting facial fat, it seems slightly perverse that any celebrity should have to sacrifice one part of her body for another.

Even in the somewhat less exalted circles of my friends, there are a number who are not quite ready to give into the middle-aged spread, any more than they’re about to lie down and give up the fight against saggy and crumply bits and, as one particularly goddess-like creature responded when I told her I was researching this piece: “I’m 45 and don’t intend to put on a pound to save my face.” In fact she’s just lost two stone and is, after years of vain attempts, as slim as she was in her twenties, thanks in part to sorting out an underactive thyroid. “If – and there’s a way to go – my face does start to look drawn, I’ll fill it until it doesn’t,” she adds defiantly. “If necessary I’ll fill it with fat from my arse.”

Far be it for me to undermine anyone’s decision not to let it all go, but at the same time I can’t help thinking that any 40-plusser who strives for exactly the same body she had in her twenties, before babies and a thousand delicious meals left their mark, is on a hiding to nothing – or at least a solitary life spent in the gym and the salon. But such is the pressure nowadays to be not just slim, but super-slim, that it often seems that what women want isn’t simply the perfectly reasonable package of a niceish bum and face, but eternal teenage-dom.

Perhaps the real crux is not which to nurture, but how to make them both feel loved. Lord knows, once your forties arrive, tending to both is almost as time-consuming and challenging as dealing with two demanding, illogical toddlers. Although all the science devoted to keeping us young ought to mean that one can keep all one’s cheek butts in tickety-boo condition, the hard facts suggest that this is the case only for a fortunate few. Deneuve herself, despite clearly not starving herself, has managed to retain such beautiful elasticity only with a little help. Other women who think they are winning the battle and cheating nature – keeping skinny and having fat injections – end up cheating themselves. You need to find an exceptionally skilled doctor to avoid that slightly pinched, or conversely that rather swollen Rice Krispie-soaked-in-milk look.

That doesn’t mean our expectations of ageing should be the same as those of our parents’ generation. Dr Cecilia Tregear, who has extensive experience in dermatology, nutrition and antiageing medicine, believes passionately that gaining weight, thinning hair, brittle bones, depleted energy stocks and lacklustre skin are not an inevitable part of getting older. “It’s absolutely a question of getting the right nutrition, which is very individual,” she says. Tregear is a great proponent of assessing patients with sleep, energy and weight problems for food intolerances, and while it may seem faddy, she has achieved dramatic results. She also believes in moderate as opposed to punishing exercise. Low-impact and weight-bearing workouts are fine, but pounding a treadmill is, she believes, counter-productive past a certain age, encouraging sag in the facial muscles. Was there ever better news on the gym front?

“Once the diet is right,” says Tregear, “you can start having Botox and fillers if you like, although any surgeon who recommends a facelift to a woman before she’s had the menopause is wasting her time and money. After her hormones have dropped she’ll just need a second one.”

Decisions about Botox, facelifts and hormone replacements are all serious, and probably best taken after consulting the experts. However, nutrition is an area in which we can all assume some responsibility and control. Vicki Edgson, a nutritionist who specialises in hormonal imbalances and antiageing areas and co-presents Channel Five’s Diet Doctors, believes that as we get older it’s important to replenish the foods in the body that mimic hormones, as their levels decrease when we age. “From a nutritionist’s point of view women don’t just look gaunt when they insist on being as slim as their daughters, their skin is affected – primarily because as we age the collagen starts to slow down its rate of reproduction. You can end up with skin that looks washed out, thickened and has a pallor that no make-up can cover.’’

Staying out of the sun is another imperative. “Skin that’s slightly leathered from time spent in the sun is very hard to retrieve, unless you go for deep acid peels, because you have to get down to the dermal layer to feed the skin both from inside and out.”

“If you want to be ultra slim,” says Amanda Ursell, The Times’s nutritionist, “make sure you’re eating enough foods – and in particular protein. Don’t think that a bit of tuna or chicken is enough. You should have some protein in every meal.”

No one here is advocating being several stone overweight as the price you have to pay for supple skin – fat women might have lovely, plump skin, but an out-of-shape body can be just as ageing as a lined face. This, it seems to me, is much more about not trying to emulate the body of a teenager. It’s about eating and exercising right, good posture, wearing fashionable, flattering clothes – and challenging the precept that if slim is good, skinny is better. For much as I’ve been influenced over the years by all the fashion shows I go to (I admit I’d much rather be slim than not slim), I’d go for the face every time on the assumption that no one’s looking at your bottom when you’re sitting down. And sitting down is what I like doing best.

The diet guru: eat little, often

Vicki Edgson, presenter of Diet Doctors on Channel 5

Phyto-oestrogens are key as we get older but our bodies aren’t used to eating soya beans, soya milk and tofu every day. To suddenly go overboard can lead to intolerances.

We also need to consume other foods to support good hormonal balance – such as liver supporting foods (there are large quantities of oestrogen in the liver). Key superfoods to help this are artichokes, asparagus, spring onions, garlic, fennel, radicchio and endives. As we get older it’s not just a question of watching the calories, it’s better to follow the old adage and eat little, often. That said, as I hurtle towards 50, it seems to me that the biggest problem with the fashionable approach is that women feel that they have to be slim at all costs. If you’re a size 8 and in your late thirties, forties or even into your early fifties, unless you’re under 5ft 3in, you will pay the price by looking much gaunter in the face.

The nutritionist: eat protein

Amanda Ursell, Times nutritionist

Women, particularly those in their thirties and forties, often go for the ultra-slim look. But one problem is that they don’t eat enough protein. We need protein to stimulate the collagen and elasticity in the skin. When women yo-yo between putting on weight and losing it, stress is put on the skin, so everything becomes less elastic and bouncy.

Here are two tips. Decide which one you want to go for, ie, the bum or the face, and stick with it. If you want to be ultra-slim make sure you’re eating enough of the right food – and in particular protein. Don’t think that a bit of tuna or chicken is enough, you should have some protein in every meal. Even if it means having a skimmed milk cappuccino or an egg – or even egg whites for the super keen – for breakfast. For lunch don’t just pick at a salad but add some lean turkey, chicken or tuna, and then in the evening, if you are slimming and you just eat steamed vegetables, add some baked or steamed fish.

You also need vitamin C for the collagen making process, from sources such as berries. Strawberries and raspberries contain ellagic acid, a good antioxidant that helps to diminish the pollutants that break down collagen. Also avoid foods cooked at a high temperature: it’s better to steam fish than to grill it. If you grill or fry foods they release toxins – age-related glycolic toxins – that cause breaks in the collagen and elastin.

Vitamin E is also good for skin. If you want to preserve the face, wheatgerm, wholegrain foods and avocado all contain vitamin E. Fish oils contain protein omega fats to keep the skin hydrated too. Every single cell needs omega to keep it watertight. It’s worth increasing your intake via soya milk or tofu.

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