Obesity and novel management of inflammatory bowel disease

Table 1 Relationship between obesity and inflammatory bowel disease (obesity as a precursor to the onset of inflammatory bowel disease)

Ref.	Study design and study population	Key findings
Khalili et al[15], 2015	United States Nurses’ Health Study cohort study: Prospective cohort study of United States women (n = 111498 women); BMI at age 18, baseline, and every 2 yr since baseline was obtained; 2028769 person-years of follow up. CD (n = 153); UC (n = 229)	Obesity at age 18 was an independent risk factor for the development of CD compared to normal BMI (aHR = 2.33, 95%CI: 1.15-4.69). No association between BMI at age 18, baseline BMI, and updated BMI and risk of UC. Higher weight gain was associated with increased risk of CD (Ptrend = 0.04). A greater magnitude of weight gain (from age 18 to age at enrolment) associated with increased risk of developing CD (weight gain > 13.6 kg vs < 2.3 kg, HR = 1.52, 95%CI: 0.87-2.65). No association between weight change (from age 18 to baseline) and risk of UC (Ptrend = 0.17) (weight gain > 13.6 kg vs < 2.3 kg, HR = 0.92, 95%CI: 0.60-1.40)
Harpsøe et al[101],2014	Danish National Birth Cohort study: A large population-based cohort study (n = 75008 women); BMI: Obtained at study baseline (based on prepregnancy body weigh); median 11.4 yr of follow-up. CD (n = 138); UC (n = 394)	An increased risk of developing fetal CD in both underweight (HR = 2.57, 95%CI: 1.30-5.06) and obese women (HR = 1.88, 95%CI: 1.02-3.47) compared with normal-weight women, pointing to a U-shaped association. No association between pregnancy obesity and risk of developing UC (HR = 0.77, 95%CI: 0.48-1.25)
Jensen et al[16], 2018	Copenhagen School Health Records Register cohort study: Cohort from the Copenhagen School Health Records Register (n = 316799); relationship between BMI in the ages of 7 to 13 yr and adult-onset IBD; BMI: Obtained at ages 7 through 13 yr; approximately 10 million person-years of follow-up. CD (n = 1500); UC (n = 2732)	Obesity in early adolescence (at each age from 7 to 13 yr) increased the risk of CD diagnosed before age 30 yr (HR = 1.2, 95%CI: 1.1-1.3) while decreasing the risk of UC (HR = 0.9, 95%CI: 0.9-1.0). No associations between changes in BMI between 7 and 13 yr and later risk of CD or UC
Chan et al[17], 2022	Pooled analysis of 5 prospective cohort studies from the Dietary and Environmental Factors IN-IBD study (n = 601009): BMI: Obtained at study baseline and during follow-up period; 10110018 person-years of follow-up. CD (n = 563); UC (n = 1047)	Obesity was associated with an increased risk of older-onset CD but not UC. The risk of developing CD increased in obese patients compared against those with a normal BMI (aHR = 1.34, 95%CI: 1.05-1.7, I2 = 0%). Each 5 kg/m2 increment in baseline BMI was associated with a 16% increase in risk of CD (aHR = 1.16, 95%CI: 1.05-1.22; I2 = 0%). With each 5 kg/m2 increment in early adulthood BMI (age 18-20 years), there was a 22% increase in risk of CD (pooled aHR = 1.22, 95%CI: 1.05-1.40, I2 = 13.6%). An increase in waist-hip ratio was associated with an increased risk of CD that did not reach statistical significance (pooled aHR across quartiles = 1.08, 95%CI: 0.97-1.19, I2 = 0%). No associations were observed between measures of obesity and risk of UC. For every 5 kg/m2 increase in BMI, the multivariable-adjusted HR was 1.00 (95%CI: 0.90-1.05). For every 5 kg/m2 increase in early adulthood BMI, the multivariable-aHR for UC was 1.05 (95%CI: 0.90-1.22, I2 = 0%)
Chan et al[18], 2013	European Prospective Investigation into Cancer and Nutrition-IBD study (n = 300724): BMI: Obtained at study baseline and during follow-up period. CD (n = 75); UC (n = 177)	No associations with the four higher categories of BMI compared with a normal BMI for UC (Ptrend = 0.36) or CD (Ptrend = 0.83). The lack of associations was consistent when BMI was analyzed as a continuous or binary variable (BMI 18.5 < 25.0 vs ≥ 25 kg/m2). Physical activity and total energy intake, factors that influence BMI, did not show any association with UC (physical activity, Ptrend = 0.79; total energy intake, Ptrend = 0.18) or CD (physical activity, Ptrend = 0.42; total energy, Ptrend = 0.11)

BMI: Body mass index; IBD: Inflammatory bowel disease; aHR: Adjusted hazard ratio; CI: Confidence interval; CD: Crohn’s disease; US: Ulcerative colitis.