A link between obesity and ovarian cancer has been highlighted by a study of almost 95,000 women.
Researchers in the US found that among women aged 50 to 71 being obese raised the risk of the disease by almost 80 per cent.
An association between high body mass and ovarian cancer was already known, but the new study provides powerful confirmation of the link.
The research also underlines the way hormones play a role in the way body fat influences cancer risk.
The association was only seen in women who had never used hormone replacement therapy (HRT) after the menopause. No link between body weight and ovarian cancer was evident among women who had been on HRT.
The findings, reported in the journal Cancer, support the hypothesis that obesity may enhance ovarian cancer risk through hormonal effects.
Dr Michael Leitzmann, from the US National Cancer Institute, and colleagues wrote: "The observed relations between obesity and ovarian cancer risk have relevance for public health programmes aimed at reducing obesity in the population."
A total of 303 women in the study group developed ovarian cancer over a period of seven years.
Among women who had never taken hormones after the menopause, obesity increased the risk of the disease by almost 80 per cent.