It's one of the big showbusiness secrets: when the stars show off their 'perfect' figures, many of the bodies we see really belong to someone else.
As a TV show prepares to tell all, Rachael 'The Body' Carr reveals the inside story of life as a body double...
To anyone but the most practised observer, Kylie is the sole star of this advert for H&M. Which is true, of course, but only up to a point. For it's actually my body that is filmed.
Forget plastic surgery and airbrushing, we celebrity body doubles are the big secret of the entertainment industry. Look hard enough and you'll find us everywhere - from pop videos and adverts to films and magazines.
For the past three years, I've been working as a celebrity body double and have seen parts of my body 'stolen' by some of the world's biggest female stars.
Body doubling was never a great career ambition. In fact, before I became involved in the industry, I had no idea that this kind of model even existed.
I grew up in Scunthorpe, Lincolnshire, and my parents were both headteachers. I always dreamed of making it as a singer, so I went to the Italia Conti stage school in London. I was there with Kelly Brook and the girls from Eternal and Liberty X.
I left with a recording contract for our six-piece pop group Boom! We had a few hits and even toured with Westlife but we split up after three years. That was when I started going to modelling castings to make a bit of money while I thought about what to do next.
One day in 2005 I was called to a casting where they wanted a girl who was exactly 5ft 2in tall, weighed 7st and had a 23in waist. I was asked to dance in a bikini. The following day I was called back and told that the job was to be a body double for Britney Spears on Pepsi's ' Gladiator' advert. I was stunned, euphoric - and terrified.
I met Britney in Rome on the shoot. Of all the celebrities I've known, she has the largest entourage - never fewer than 20 people - but she was so sweet. 'Oh my God, you're so cute,' she shrieked when she saw me.
She was there for two days, during which she did all the dance routines. I watched her like a hawk all the time. I needed to capture her dance moves perfectly so when there were any shots that didn't require Britney's face on the screen, I could take her place. We worked two 20-hour days and I never heard her complain once.
After she left - a star of her stature doesn't come cheap, so the aim is to keep her on set for as little time as possible - I was there for another couple of weeks. When I arrived home I was touched to find Britney had sent me a pair of boots that I had admired.
After that, offers of body-double work just kept coming in. Once stars and their people realise that you are professional and you aren't going to start asking for autographs or behaving as if the star is your new best friend - the two cardinal sins of body doubling - then they're happy to keep using you.
Since that first shoot three years ago, I've worked with Kylie several times, with Christina Aguilera and with Britney again.
The H&M advert I filmed with Kylie took two weeks in Acapulco, Mexico. She is easy-going and always works with the same people - they're like a family.
She is my favourite celebrity to work with and she's also the closest to me in size. That's why, before she went on tour, I did all her costume and prop fittings. While she was rehearsing in the studio, I would be on the stage to ensure that everything from microphone stands and chairs were the right size.
Last year, I did the Christina Aguilera 'Here To Stay' Pepsi advert, which sees her transported to Britain, America, the Czech Republic, Japan and India in eight days. Actually, I did the travelling - Christina did all her filming in a studio in America.
I'm always running into other doubles. I've met the body doubles for everyone from Beyonce to Enrique Iglesias.
Although I usually double for the whole body from the head down, other models specialise in specific body parts. Nina 'The Hand' is the queen of hand models and her perfect digits sometimes feature in several different adverts in the same magazine. Kayko 'The Legs' can earn £60,000 a year, while Colin 'The Feet' is used to make some of the best footballers in the world look better than they really are.
Obviously, most body doubles have a shelf life linked to the career of the stars they double for, but I'll keep doing it for as long as people want me. I'm only 29 and Kylie's 40, and she seems to go from strength to strength.
However, I've also trained as a make-up artist as a preparation for the future - showbusiness is precarious and it's sensible to have a plan B.
The obvious pitfall of basing your career on how good your body looks is the pressure to stay perfect. I have to work out regularly and be strict about what I eat and drink.
My body is a temple but it does need occasional refurbishment: I've had two boob jobs and I've had my bottom resculpted. It would be hard to survive in this game without it, especially when all the celebrities have work done.
I don't really have a favourite part of my own body, and despite being considered 'perfect', I do have 'fat days' like anyone else. And I, too, experience a flutter of envy when I see a star's perfect body in a commercial or video. It's sometimes hard even for me to remember that it's probably not their body.