OBJECTIVE: To investigate whether overall obesity (as measured by BMI) and abdominal obesity (as measured by waist-to-hip ratio adjusted for BMI) are associated with gout risk and serum urate concentrations using Mendelian randomization. METHODS: Single nucleotide polymorphisms associated with BMI (n = 97) and waist-to-hip ratio adjusted for BMI (n = 49) were analysed for association with gout risk in 2115 gout cases and 67 259 controls, and with serum urate concentrations in 110 347 individuals from the Global Urate Genetics Consortium. RESULTS: Genetically higher BMI, but not waist-to-hip ratio adjusted for BMI, was positively associated with risk of gout and serum urate concentrations. Each standard deviation (about 4.6 kg/m2) increase in genetically predicted BMI was associated with an odds ratio of gout of 2.24 (95% CI 1.70, 2.95; P = 8.4 × 10-9) and with a 0.30 mg/dl (95% CI 0.25, 0.35; P = 1.6 × 10-36) increase in serum urate concentrations. CONCLUSION: These findings provide support that overall obesity may be a risk factor for gout and is associated with higher serum urate concentrations.