The current epidemics of obesity and gastroesophageal reflux disease (GERD)-related disorders have generated much interest in studying the association between them. Results of multiple studies indicate that obesity satisfies several criteria for a causal association with GERD and some of its complications, including a generally consistent association with GERD symptoms, erosive esophagitis, and esophageal adenocarcinoma. An increase in GERD symptoms has been shown to occur in individuals who gain weight but continue to have a body mass index (BMI) in the normal range, contributing to the epidemiological evidence for a possible dose-response relationship between BMI and increasing GERD. Data are less clear on the relationship between Barrett's esophagus (BE) and obesity. However, when considered separately, abdominal obesity seems to explain a considerable part of the association with GERD, including BE. Overall, epidemiological data show that maintaining a normal BMI may reduce the likelihood of developing GERD and its potential complications.