Effect of body-mass index on the risk of gastric cancer: A population-based cohort study in A Japanese population

•BMI ≥ 27 kg/m2 was associated with increased gastric cancer risk among men.•U-shaped increase in the risk was observed for proximal gastric cancer.•With H. pylori infection, BMI ≥ 27 kg/m2 increased proximal gastric cancer risk. Body fatness and weight gain are considered probable causes of gastric cancer, specifically in the cardia region. However, limited evidence is available in Asia, where the burden of gastric cancer is high. The objective of this study was to determine an association between body-mass index (BMI) and gastric cancer risk using a large population prospective cohort. 92,056 subjects enrolled in the Japan Public Health Center-based prospective Study who reported their height and weight were followed up until the end of 2013. A Cox proportional hazards model was used to estimate the risk for gastric cancer and its subsite based on baseline BMI. A subgroup analysis was conducted taking account of Helicobacter pylori (H. pylori) infection and atrophic gastritis status. 2,860 gastric cancer cases (2,047 men, 813 women), 307 proximal gastric cancer cases (244 men, 63 women), and 1967 distal gastric cancer cases (1,405 men, 562 women) were found during the follow-up period. Among men, baseline BMI ≥ 27 kg/m2 increased the risk of overall gastric cancer (hazards ratio (HR) 1.23, 95% confidence interval (CI) 1.00–1.53). For both sexes, U-shaped increase in the risk was observed for proximal gastric cancer. Subgroup analysis showed a statistically significant association between the risk of proximal gastric cancer and BMI ≥ 27 kg/m2 among those who were atrophic gastritis positive, H. pylori antibody positive, and those who tested positive to either or both atrophic gastritis and H. pylori antibody. Our result suggests that gastric cancer risk increases for men with BMI ≥ 27 kg/m2.