Two thirds of women have lied about their size, with 9lbs being the average amount by which they reduce their true weight.
Researchers found millions of women fib about their weight with many ‘losing pounds’ when talking to a partner, best friend and even their mum.
The average women removes 9lbs from the scales and one in five has even pretended they weigh a stone less than they actually do.
One in six gone as far as typing in a lower weight into the machines at the gym as they are embarrassed by their true size.
Because of the lies, a quarter of women are now confused about their true weight and regularly buy the wrong sizes.
The study of 2,000 women was commissioned by Eat Water, a pasta product that encourages weight loss.
And it isn’t just their weight that women lie about, with many confessing to telling porkies about their dress size, bra size and even their shoe size.
Vincent Lee, from EatWater.co.uk, said: ‘Most people will admit to telling the odd white lie about their body shape and weight but for women to be lying so frequently is a bit of a shame.
‘Weight is such a tricky issue and everyone knows that it’s not always the best indicator of someone’s healthiness or size. And body shape and size is such a personal issue.
‘Carrying extra weight can be embarrassing and knock your confidence and it’s only natural that you might not want to highlight this to your friends and even your partner.
‘It’s especially worrying that so many women are starting to believe their own lies.’
Most women admit to dropping one dress size but one in five said they always claim they are two dress sizes smaller than reality.
And 17 per cent even cut out the labels from clothes and bras to keep up the pretense of being smaller.
The findings also found one in ten even lie about their height with most adding a few inches to make themselves seem taller.
The top reason for fibbing was that women were embarrassed by their true size, followed by giving them an instant confidence boost.
More than half of those polled said that all women lie about their size so it was more or less ‘expected’.
The results showed that most women wanted to be between eight and nine stone and a size 10 with a bra size of 34C.
They also wanted to have size five feet and be between five foot six inches and five foot eight inches.
Vincent Lee added said: ‘Losing a few pounds isn’t as hard as you can often think it will be.
‘Simply watching what you eat and making sure you don’t eat too many carbohydrates or calories and you have a balanced diet doesn’t have to be a chore.
‘Or mean that you have to cut out your favourite foods.
‘Eat Water is a range of pasta, noodles and rice that contains virtually zero calories, carbohydrates, fats, saturates, sugars and salt
‘Eat Water allows you to still have a tasty filling meal but without the guilt.’