Obesity is rapidly becoming a serious health risk in the Unites States affecting both young and old alike. More than 30% of men being classified as obese. The U.S. Surgeon General stated in 2003 that obesity is the fastest-growing cause of disease and death in America. The American Cancer Society in 2006, declared that prostate cancer is under diagnosed in younger obese men and obesity may be associated with more aggressive cancers with poor clinical outcome. Obesity has now been identified as an independent negative prognostic indicator of disease free survival following radical prostatectomy and a retrospective study indicated that early onset obesity increased the risk of mortality from prostate cancer. Hypothesis: Obesity, both early in development as well as later in life, will increase both the incidence and the severity of prostate cancer. We will test this hypothesis in clinically relevant animal models. The non-invasive imaging and quantification technologies developed in this proposal and their application to the study into the effects of exposure, and time of exposure, to risk factors using mouse models of human disease will have broad applicability across many platforms of cancer research such as, cancer intervention, prevention and the identification of bio- and molecular-markers of cancer progression.