An online guru called the Carbon Coach takes you through simple lifestyle changes that can reduce your carbon footprint.

Joining Sienna in the battle for environmental fitness, set up by charity Global Cool, are Josh Hartnett and Heather Graham.

Heather, who has committed herself to saving 1.5 tonnes of carbon through the new ’diet’, said: "Think of it as a new workout, a simple, straightforward workout to save the planet."

Sienna annoys neighbours - May 25 2007
Sienna Miller’s neighbours have apparently spoken out about the blonde actress’ late night parties.

The Factory Girl star is well known for her love of partying - but it seems her neighbours aren’t quite so keen and the nearby residents of Sienna’s pad in Marylebone, North-West London, say the noise during the early hours is unacceptable.

One told the Independent: "She has parties with bouncers outside that sometimes last until daylight.

"The music’s so loud it rattles our windows. When someone’s gone round to complain, the music’s turned down a bit then turned up when they’ve gone. We’re going to call the noise police if it carries on."

The curtain-twitching neighbour also added that it has been more peaceful in the area for the past three weeks - because Sienna has been filming the Dylan Thomas biopic, the Edge Of Love, alongside Keira Knightley and Matthew Rhys, in Wales.

The neighbour moaned: "I am dreading her coming back because the music will start again."

A spokesperson for the actress said they did not comment on her private life.

Sienna does Hippie Hippie Shake - May 4 2007
Sienna Miller is to star alongside Cillian Murphy in a film about 1960s London, according to reports.

The pair will star in Hippie Hippie Shake, about Australian magazine editor Richard Neville who became embroiled a landmark obscenity trial after publishing a sexually explicit edition of Oz magazine.

The Hollywood Reporter says Cillian, 27, will take on the role of Neville, with Sienna playing his partner Louise Ferrier.

The screenplay has been written by Lee Hall, who wrote Billy Elliot, and will be directed by Bridget Jones: The Edge Of Reason’s Beeban Kidron. Shooting is expected to being in London this autumn.

Sienna is currently working with Cillian on Dylan Thomas biopic The Best Year Of Our Lives. The 25-year-old is no stranger to playing 1960s sirens, having starred as Edie Sedgwick in Factory Girl.

Cillian is quickly establishing a reputation as an impressive performer, following roles in Batman Begins, The Wind That Shakes The Barley, and Girl With A Pearl Earring.

Sienna bags Lindsay’s old role - April 24 2007
Sienna Miller has stepped in to fill Lindsay Lohan’s shoes, starring opposite Keira Knightley in The Best Days Of Our Lives, after the flame-haired starlet pulled out at the last minute.

Li-Lo was due to move to the UK at the weekend to start work on the film, which is scheduled to start filming in London and Wales on May 7.

But the actress passed on the role - and the move - after failing to reach an agreement over her contract with the film’s financiers, according to Variety.

With a script penned by Keira’s playwright mum, Sharman Macdonald, the film tells the story of poet Dylan Thomas, who will be played by Matthew Rhys, and the two women vying for his affections.

Sienna will replace Lindsay as Dylan’s wife Caitlin, while Keira will play Vera Phillips, his free-spirited childhood friend.