LEP and atrial fibrillation: Univariable MR analyses were applied to identify potential mediators, and then the multivariable MR analyses were conducted to explore the mediated roles of circulating biomarkers, metabolic markers and comorbidities in the association between BMI and AF.<h4>Results</h4>This MR study found a significant causal association between BMI and AF (OR = 1.41, 95% CI = 1.33-1.50; <i>p</i> < 0.001), which was attenuated to 1.21 (95% CI = 1.03-1.43) after being adjusted for leptin, in which 48.78% excess risk was mediated.