The Oscars red carpet is often referred to by the celebrity press as the most powerful catwalk in the world. It is the gilded stage for which haute couture dresses are made; bright lights fall on film stars dressed by the world's most accomplished designers in some of the most expensive items of clothing ever made.

But for many of the nominees, what goes on in the run-up to Oscar Sunday involves weeks of hunger, sacrifice and last-minute liposuction. "It is brutal," British facialist Nichola Joss told the New York Times this week, of the pressure of the high-definition closeup on Hollywood actors. "You can see a hair follicle. You can see a pimple before it is a pimple."

Hollywood insiders talk of actors who plot their beauty treatments at different points around Los Angeles in a bid to lose photographers between pedicure appointments and derma-filler treatments. Anti-anxiety pills such as Xanax are said to be widely used by nominees.

"The entire city stops normal activity and the Oscars take over; the atmosphere is surprisingly serious," says gossip columnist Dean Piper, who is in LA to cover the Oscars. "Most of the A-list have been through the St Tropez tanning suite at the Four Seasons by now, so their skin colour can settle for Sunday. But I'm seeing stylists whooshing around town in their Range Rovers, pulling gowns from boutiques where they are being altered, and the nail bars are heaving. The actresses I've seen at 'lunch' are simply pushing leaves around their plate."

High-definition photography and the prevalence of social media means that actors now face having the minute details of every angle of their body and face appear in hundreds of photos online. As a result, the stakes for red-carpet glamour have never been higher.

"You know it's the Oscars because suddenly everyone is on the cayenne and lemon juice diet, and talking about appointments with their facialist, podiatrist, personal trainer, stylist, dietitian, hairdresser and teams from the big fashion houses like Valentino or Dior," says one well-known Hollywood stylist.