Researchers from the UK, US, Denmark, The Netherlands, Sweden and France set out to explore the association between obesity and risk of Crohn′s disease (CD) and ulcerative colitis (UC) in a pooled analysis of five prospective cohort studies. These studies had measurements of body mass index (BMI) and waist-hip ratio and included 601,009 patients. There were 563 incident cases of CD and 1047 incident cases of UC over the mean follow-up of 16 years. 

Results showed that patients with baseline BMI ≥30 kg/m2 were at increased risk for CD with pooled adjusted hazard ratio of 1.34 compared with those with normal BMI ranging between 18.5 and less than 25 kg/m2.A 16% increase in risk of CD was noted for every 5 kg/m2 rise in baseline BMI (pooled aHR 1.16). Likewise, every 5 kg/m2 increase in BMI between 18 and 20 years of age was correlate with 22% increase in the risk of CD (pooled aHR 1.22). Although the risk for CD increased with increase in waist-hip ratio, this association was not statistically significant. But no such associations were observed for ulcerative colitis. The study therefore concluded that obese adults were at increased risk for CD, but not UC. 

Chan SSM, et al. Clin Gastroenterol Hepatol. 2022 May; 20(5):1048-1058.