The effects of excess weight on the development of cancers are controversial, and little is known for populations outside the United States and Europe. We conducted this study to assess the effects of excess weight with a large cohort of Koreans. We assessed the relationship between body mass index (BMI) and various cancers in a 10-year follow-up cohort of 781,283 Korean men who were free of prior cancer at baseline. Weight and height were measured, and questionnaires related to health behaviors and medical history were completed. Data on newly developed cancers were obtained from two organizations in Korea. A proportional hazards model was used to examine the relationship between BMI and cancer. Adenocarcinoma in the colon and rectosigmoid, hepatocellular carcinoma, cholangiocarcinoma, adenocarcinoma in the prostate, renal cell carcinoma, papillary carcinoma in the thyroid, small-cell carcinoma in the lung, non-Hodgkin's lymphoma, and melanoma had positive dose-dependent relationships with BMI (all P < .05). Although no linear trend was found (P = .267), obese men who never smoked with a BMI of >or= 30 kg/m(2) had an increased risk of developing gastric adenocarcinoma (relative risk = 1.73). Other cancers, such as leukemia, multiple myeloma, and gallbladder and pancreatic cancer, did not show significant associations. These findings show that, even in Koreans, obesity clearly increases the risk of many types of cancers and the strength of the associations varies with the organ and histologic type. Because these obesity-related cancers are reported to be rapidly increasing in Korea and many other Asian countries, controlling obesity epidemics could be an effective tool for preventing these cancers in these areas.
