AIM: To comprehensively investigate the long-term risk of all-cause mortality associated with general and central obesity in patients with inflammatory bowel disease (IBD). METHODS: Overall, 5107 IBD patients [mean age 57.0 (SD: 8.0) years; 51.7% female] were included in the prospective cohort. General obesity was assessed using body mass index (BMI), while central obesity was evaluated using hip circumference, waist circumference (WC), waist-to-hip ratio (WHR), weight-adjusted waist index (WWI), conicity index (CI) and A Body Shape Index (ABSI). Primary outcome was all-cause death. Cox proportional hazards models were employed to examine the associations. RESULTS: During a median of 14.6 years' follow-up, 591 all-cause deaths occurred. At baseline, 1681(32.9%), 2229(43.6%), 1161(22.7%) and 36(0.70%) patients were BMI-defined normal, overweight, obesity and underweight. Underweight individuals had a 2.22-fold increased mortality risk than those with normal BMI (HR = 3.22, 95% CI:1.70-6.11), while null associations were observed for overweight or obesity. As for central obesity, individuals with the highest quartiles of WC (HR = 1.34, 1.02-1.76), WHR (HR = 1.56, 1.13-2.15), WWI (HR = 1.64, 1.24-2.16), CI (HR = 1.72, 1.28-2.30) and ABSI (HR = 1.64, 1.23-2.20) had a 34%, 56%, 64%, 72% and 64% greater mortality risk versus the lowest quartiles, with significant dose-response relationships (all P values < 0.05). CONCLUSIONS: Central obesity and underweight, rather than general obesity, are associated with an increased risk of all-cause mortality in IBD patients. These findings underscore the importance of adequate nutrition and reduced visceral adiposity for long-term prognosis improvement of IBD patients.