This cross-sectional study reports associations between anthropometric measures, serum antioxidant concentrations, and present diet with measures of elevated cell proliferation in 51 patients with Barrett's esophagus. Cell proliferation was assessed as fractions of cells in the S and G2 phases, measured in biopsies of Barrett's tissue and analyzed by DNA content flow cytometry. Elevated proportions in the S and G2 phases predict progression to adenocarcinoma. The percentage of cells in the S phase was positively associated with waist-to-hip ratio (r = 0.33, p < 0.05) and negatively associated with serum and dietary selenium (r = -0.34 and -0.32, respectively, p < 0.05). The percentage of cells in the G2 phase was positively associated with weight change from age 25 (r = 0.39, p < 0.01) and negatively associated with dietary selenium (r = -0.31, p < 0.05). Selenium from breads and grains was negatively associated with the percentage of cells in the S phase (r = -0.41, p < 0.01) and the percentage of cells in the G2 phase (r = -0.41, p < 0.01). These results suggest that increasing weight gain in adulthood, increasing waist-to-hip ratio, and decreasing dietary selenium intake and serum levels increase the risk of progression of Barrett's esophagus to adenocarcinoma.