Obesity is associated with increased risk of Crohn’s disease, but not ulcerative colitis: A pooled analysis of five prospective cohort studies

Background and Aims: It is unclear whether obesity is associated with the development of inflammatory bowel disease despite compelling data from basic science studies. We therefore examined the association between obesity and risk of Crohn's disease (CD) and ulcerative colitis (UC). Methods: We conducted pooled analyses of 5 prospective cohorts with validated anthropometric measurements for body mass index (BMI) and waist-hip ratio and other lifestyle factors. Diagnoses of CD and UC were confirmed through medical records or ascertained using validated definitions. We used Cox proportional hazards modeling to calculate pooled multivariable-adjusted HRs (aHRs) and 95% confidence intervals (CIs). Results: Among 601,009 participants (age range, 18-98 years) with 10,110,018 person-years of follow-up, we confirmed 563 incident cases of CD and 1047 incident cases of UC. Obesity (baseline BMI ≥30 kg/m 2) was associated with an increased risk of CD (pooled aHR, 1.34; 95% CI, 1.05-1.71, I 2 = 0%) compared with normal BMI (18.5 to