The risk of developing aggressive prostate cancer can be worsened by being an unhealthy weight and having a large waistline, a study has found.
Researchers found that every 4in (10cm) increase in waist circumference can increase a man's chances of developing fatal prostate cancer by 18%.
Similarly, the risk of being killed by a fatal strand of the disease shoots up if the man has a high body mass index (BMI), the report says.
The study, by scientists at the University of Oxford, examined more than 140,000 men with a mean age of 52 years, across eight countries.
After 14 years, some 7,000 incidents of prostate cancer were identified, of which 934 were fatal.
It also found that high-grade prostate cancer, an aggressive form of the illness, was exacerbated by obesity.
There was a 13% increase in the risk of developing it for every 4in (10cm) of waistline gained.
The study, which was funded by Cancer Research UK, said: "The findings from this large prospective study show that the association between body size and prostate cancer is complex and varies by disease aggressiveness; men who have greater adiposity have an elevated risk of high grade prostate cancer and prostate cancer death."
"Our results are in line with health advice for other non-communicable diseases.
"Men should try to maintain a healthy weight."
A spokesman for Prostate Cancer UK said: "Maintaining a healthy weight and staying active can protect against many diseases, including cancer.
"This research adds to a growing body of evidence that shows that weight and waist size could be another crucial risk factor for men to be aware of when it comes to protecting themselves against prostate cancer."