Obese men with prostate cancer face a higher risk of their cancer worsening than men of normal weight, according to a new study.

Obese men (who have a body mass index, or BMI, of 30 or higher) are three times more likely to have their cancer progress to a more advanced stage than men of normal weight, the study said. They are also three times more likely than non-obese men to have the cancer spread to their bones, and five times more likely to have the cancer spread to other parts of the body.

The finding holds true even when the obese men are treated with androgen deprivation therapy, which is the administration of a chemical that stops the production of testosterone that fuels prostate tumors, researchers said.

One possible reason for the obese men's poor outcomes is that they may require a higher dose of androgen deprivation therapy than they are currently receiving, said study researcher Dr. Christopher J. Keto, a urologic fellow at Duke University Medical Center in North Carolina. Right now, the dose is the same for all men, regardless of their weight.

Prostate cancer is the second deadliest cancer for men, and will affect about one in six U.S. men in their lifetimes, according to the American Cancer Society.

Keto and his colleagues looked at the health information of 287 men who were diagnosed with prostate cancer and whose prostates had been removed at one of five U.S. Department of Veteran Affairs hospitals between 1988 and 2009. All of the men had received androgen deprivation therapy as a treatment for their cancers.

"By being thematic in our research we can really get to the bottom of something," study researcher Dr. Stephen J. Freedland, an associate professor of urology at the Duke Prostate Cancer Center, said in a statement. "The study supports a growing body of literature showing that obese men with prostate cancer do worse. Our next step is to figure out why."

The study shows that doctors need to come up with better interventions for obese men who have prostate cancer, particularly ones that focus on promoting diet and exercise in addition to prostate cancer treatment, Freedland said.

Past studies have also shown that obesity affects the recurrence of prostate cancer. A 2005 study in the journal Urology showed that very obese men (with a BMI of 35 or higher) were 1.69 times more likely to have a recurrence of prostate cancer than men of normal weight.

The new study was presented May 15 at the annual meeting of the American Urological Association.

Pass it on: Obesity is a risk factor for prostate cancer spread.

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