A US study reported findings that not only do obese men have a higher risk of getting prostate cancer, but they are prone to more dangerous tumors. The study also showed an increased risk in men with smaller prostates. The study was conducted at a Veterans Affairs hospital in California from 1998 to 2002. It included 787 men who had biopsies for suspected prostate cancer and showed that obese men were more likely to have positive results. Obese men also have more aggressive tumors, the study showed.

While it is often a slow-growing cancer that can be watched without being treated, in some cases it can become aggressive and spread quickly throughout the body. Doctors are trying to determine which men need more immediate treatment. They suggest that obese men are more prone to aggressive tumors because obesity can interfere with testing for the disease. Fat cells produce estrogen-like compounds, which may interfere with levels of prostate-specific antigen, a protein in the blood used to determine the presence of cancer in men. Misread levels can give a false reading of "all-clear," when in fact a tumor may be present.