Increasing a skirt size over 10 years between your 20s and 50s can increase risk of breast cancer after the menopause, according to research from the University College London.
The researchers took their findings from almost 93,000 women taking part in the UK collaborative Trial of Ovarian Cancer Screening (UKCTOCS) in England.
The women were aged over 50, had gone through the menopause and had no traces of breast cancer when they entered the study between 2005 and 2010.
They were asked about their current skirt size and what their skirt size had been in their 20s. They also provided information at enrolment on BMI, reproductive health, fertility, family history of breast and ovarian cancer and use of hormonal contraceptives and HRT. All of these things are known to influence the risk of breast cancer.
After three to four years, they were asked about continuing use of HRT, general health, a subsequent diagnosis of cancer and lifestyle habits (diet, smoking etc).
During the monitoring period 1090 women developed breast cancer. After taking other influential factors into account, increases in skirt size was the strongest predictor of breast cancer risk, with analysis revealing that going up one size every 10 years increased risk by 33 per cent. Going up two sizes was associated with a 77 per cent risk.
Simon Vincent , assistant director of research at Breakthrough Breast Cancer said: 'This study highlights an easy way to monitor your weight gain over time. Women are more likely to remember their skirt size when they were younger than their BMI.'
An expanding waistline has been linked to other cancers such as those of the pancreas, lining of the womb, and ovaries.
The study was published in BMJ Open.