Why would a girl barely out of her teens deliberately want to look "done"? It's to get the year-zero face ...
Let me pinpoint the moment the world first became aware of the ageless, year-zero face: it was under the Louvre at Paris Fashion Week as 2009 drew to a smoky close.
On the Ungaro catwalk, jewel-toned bolero jackets and sequinned nipple tassels were shown, before the label's "artistic adviser" Lindsay Lohan appeared. There were gasps from the front row and a thud of damp applause. It wasn't the clothes - it was Lohan's face.
She had a forehead so taut and shiny it looked like an iPhone. Her lips were inflated and her cheek-bones looked as if they were climbing her jaw in order to dive to their death.
Each change to her then 23-year-old face seemed to nod towards youth, but in fact imply age.
This isn't to say she looked old - as she bounced down the catwalk, her hair streaming behind her, she seemed to have transcended age.
Though cosmetic surgery traditionally has been used to make patients look younger, doctors are noticing a trend for women wanting to simply look "done". Rather than chase youthfulness with a scalpel, some seem to be choosing instead to fix their faces at a certain age (celebrity dermatologist Gervaise Gerstner suggests many women settle for 36) and maintain the look with injectable fillers and cosmetic treatments.
While few celebrities will admit to having had surgery, the surgeons themselves are outspoken. "It's a matter of the right procedure on the wrong girl at the wrong time," New York plastic surgeon Douglas Steinbrech told W magazine.
"There's this new mentality that if you do not look a little bit fake, then the surgeon hasn't done his job.
"This used to be a much more prevalent idea on the west coast, but now you walk up Madison Avenue and you see these young girls with that cloned, cougar-like face.
"Either they don't know what they look like, or they want to look like they've had something done."
There's nothing new in celebrities having cosmetic surgery, but the age at which they start is falling fast.
Last year actress Charice Pempengco, 18, had Botox to look "fresh" for her role in Glee, and reality star Heidi Montag, 24, famously had 10 procedures in 10 hours. She later conceded that all the surgery made "hugging" difficult.
In America, patients under 34 account for 20 per cent of Botox procedures and chemical peels, and more than 9000 breast enhancement operations are carried out on girls aged 13 to 19. The move to look ageless, though, rather than younger, is recent, with women today encouraged by some practices to get "preventive" Botox injections.
But the more you get, some women are finding, the older you look. British consultant plastic surgeon Norman Waterhouse thinks the year-zero face is the effect of fillers being overused.
"When Botox is used with subtlety and finesse, the woman shouldn't look 'filled', she should just look less tired," he says. "And using fillers expands the skin, so if you use a lot, then as it disappears you eventually need more to plump it out, so you get trapped in a Botox cycle.
"Of course, there is a little subset of women who get work that astonishes me, turning themselves into a parody of feminine beauty - the 'party tits', the 'ice-rink Botox' - where your face is completely flat and shiny - but that, I think, is missing the point."
Those who balance it right, paparazzi photos suggest, achieve the look of the golden, ageless age: 36.
"Some people wake up at 42 and realise they need to return to 36," says Gerstner. Demi Moore is 48, but, having allegedly had £200,000 ($405,000) of surgery, including a knee lift, looks at least a decade younger. "But the people who end up looking best have been planning for it all along."
She recommends an expensive programme of Botox, lip fillers, laser skin resurfacing and glycolic peels for maintenance, all of which, administered well, promise to keep even the tautest 23-year-old looking like a 30-something with a year-zero face.