THE risk of death from prostate cancer nearly doubles in men who have put on 20 kilograms or more in their adult life, new Australian research has found.

The paper, published in the International Journal of Cancer, shows an increase in body weight during a man's adult life is associated with an increased risk of suffering an aggressive form of prostate cancer and of dying from prostate cancer.

Having a high body mass throughout life was also associated with increased risk of aggressive prostate cancer.

''This study and other similar studies have shown that obesity is related to aggressive and fatal cancer,'' said the study's co-author, Dallas English. ''Maintaining a healthy weight during adult life is really the bottom line.''

Professor English, director of the centre for molecular, environmental, genetic and analytic epidemiology at the University of Melbourne, said one of his concerns was that the study - of more than 17,000 Australian men aged 40 to 69 - drew participants from a generation in which childhood obesity was not a significant issue.

He said the higher rates of obesity among children now might worsen outcomes. ''In Australia, things have changed a lot,'' he said. ''We haven't had the experience of people growing up with childhood obesity.''