BACKGROUND AND AIM: Obesity is a recognized risk factor for new-onset atrial fibrillation (AF). The association between body fat distribution, which is measured by body mass index (BMI) and waist-hip ratio (WHR), its changes, and new-onset AF is conflicting. METHODS AND RESULTS: Participants of the European Prospective Investigation into Cancer and Nutrition in Norfolk cohort study were included, with exclusion criteria of prevalent AF, rheumatic heart disease, and cancer. AF was confirmed by the International Classification of Diseases-10 hospital discharge code I48. Adjusted sex-specific Cox proportional hazards models were used to quantify the AF risk per 1 standard deviation increase and for quintiles of adiposity indices. A total of 10,885 men and 12,857 women were followed up for a median of 19 years, yielding 451,098 person-years. New-onset AF was diagnosed in 1408 (12.9%) men and 1102 (8.6%) women. Multivariable analyses showed that BMI predicted new-onset AF in all, while WHR predicted only in men. New-onset AF risk gradually increased across the range of adiposity indices: for men in the highest BMI quintile, HR: 1.59 (CI 1.32-1.91, p for trend<0.001), whereas for women in the highest BMI quintile, HR: 1.52 (CI 1.23-1.88, p for trend<0.001). Further, for men in the highest WHR quintile, HR: 1.31 (CI 1.09-1.57, p for trend: 0.01), whereas for women in the highest WHR quintile, HR: 1.12 (CI 0.90-1.41, p for trend: 0.17). The change in BMI and WHR was similar in participants with or without new-onset AF. CONCLUSIONS: An increased body mass, as measured by BMI, is associated with an increased risk of developing new-onset AF. More abdominal fat distribution, as measured by WHR, is associated with an increased risk of developing new-onset AF in men but not in women.