The new study finds that "body mass in both younger and older adulthood and weight gain between these periods of life may influence prostate cancer risk."
The study looked at the relationship between weight and prostate cancer in blacks, Japanese, Latinos, Native Hawaiians and whites.
Researchers collected data on almost 84,000 men. More than 5,500 of them were diagnosed with prostate cancer.
Researchers found white men who gained excess weight in young adulthood increased their risk of advanced or high-grade prostate cancers.
Black men increased their risk for less hazardous, localized, low-grade forms of the disease.
Researchers said higher weight gain in older adulthood was associated with increased risk of prostate cancer among white, Hawaiian men and a decreased risk among Japanese men.
A spokesperson for the American Cancer Society said the study is not clear whether weight gain is as important as it is for other cancers.
The full report is in the September issue of Cancer Epidemiology.