Overweight women are more likely to get ovarian cancer than their thinner counterparts, researchers say.
Scientists have previously linked being overweight or obese to a number of other cancers such as those of the womb, breast and bowel.
Now experts at the World Cancer Research Fund (WCRF) have also linked being overweight to ovarian cancer.
Researchers at the British charity's Continuous Update Project (Cup) discovered the link after examining 128 studies about women with ovarian cancer.
A further analysis of 25 studies that contained data about ovarian cancer incidence and body mass index (BMI) scores suggested a six per cent increased risk of disease for every five BMI units.
Those with a BMI of 18.5 and under are considered underweight, a score of 18.5 to 24.9 is a healthy weight, a BMI over 25 is considered overweight and those who have a score above 30 are technically obese.
The report states: "There is evidence for an association between overall body fatness (marked by BMI) and ovarian cancer.
"Greater body fatness is a probable cause of ovarian cancer in women."
WCRF's head of research and interpretation, Dr Rachel Thompson, added: "We can now say with certainty that being overweight or obese increases the risk of developing ovarian cancer, just as it does with a number of other cancers such as breast, bowel and womb cancer.
"This means that women can make lifestyle changes to reduce their chances of getting ovarian cancer. Previously, we only knew about risk factors that are fixed, such as age and family history of the disease, but now we can say that keeping to a healthy weight helps reduce the risk of getting ovarian cancer."
Every year there are about 7100 new cases of ovarian cancer in the UK and about 4300 deaths from the disease.
About 57 per cent of British women are considered to be overweight or obese, which puts them at a higher risk of developing the disease.