BACKGROUND: Gastroesophageal reflux disease (GERD) is a common cause of morbidity and health-care utilization in many countries. Obesity is a potentially modifiable risk factor, but existing studies have conflicting results, possibly due to differences in study design, definitions, or populations. METHODS: We performed a systematic review and meta-analysis of studies identified using MEDLINE, the Web of Science electronic database, manual literature review, and a review of expert bibliographies. Studies were included if they: (1) evaluated obesity, body mass index (BMI), or another measure of body size; (2) included data on reflux symptoms, esophagitis, or a GERD-related hospitalization; and (3) reported a relative risk or odds ratio (OR) with confidence intervals or provided sufficient data to permit their calculation. RESULTS: We identified 20 studies that included 18,346 patients with GERD. Studies from the United States demonstrated an association between increasing BMI and the presence of GERD (95% confidence interval [CI]= 1.36-1.80, overweight, OR = 1.57, P value homogeneity = 0.51, 95% CI = 1.89-2.45, obese, OR = 2.15, P= 0.10). Studies from Europe provided heterogeneous results despite stratification for several factors; individual studies demonstrated both positive associations and no association. CONCLUSIONS: This analysis demonstrates a positive association between increasing BMI and the presence of GERD within the United States; this relationship became apparent only after stratification by country and level of BMI. These results support the evaluation of weight reduction as a potential therapy for GERD. Further studies are needed to evaluate potential mechanisms and any differences in this relationship among different study populations.