Prevalence and associated factors of obesity in inflammatory bowel disease: A case-control study

BACKGROUND In recent years, an increasing prevalence of obesity in inflammatory bowel disease (IBD) has been observed. Obesity, moreover, has been directly correlated with a more severe clinical course and loss of response to treatment. AIM To assess the prevalence and associated factors of obesity in IBD. METHODS We collected data about IBD disease pattern and activity, drugs and laboratory investigations in our center. Anthropometric measures were retrieved and obesity defined as a body mass index (BMI) > 30. Then, we compared characteristics of obese vs non obese patients, and Chi-squared test and Student's t test were used for discrete and continuous variables, respectively, at univariate analysis. For multivariate analysis, we used binomial logistic regression and estimated odd ratios (OR) and 95% confidence intervals (CI) to ascertain factors associated with obesity. RESULTS We enrolled 807 patients with IBD, either ulcerative colitis (UC) or Crohn's disease (CD). Four hundred seventy-four patients were male (58.7%); the average age was 46.2 +/- 13.2 years; 438 (54.2%) patients had CD and 369 (45.8%) UC. We enrolled 378 controls, who were comparable to IBD group for age, sex, BMI, obesity, diabetes and abdominal circumference, while more smokers and more subjects with hypertension were observed among controls. The prevalence of obesity was 6.9% in IBD and 7.9% in controls (not statistically different; P = 0.38). In the comparison of obese IBD patients and obese controls, we did not find any difference regarding diabetes and hypertension prevalence, nor in sex or smoking habits. Obese IBD patients were younger than obese controls (51.2 +/- 14.9 years vs 60.7 +/- 12.1 years, P = 0.03). At univariate analysis, obese IBD were older than normal weight ones (51.2 +/- 14.9 vs 44.5 +/- 15.8, P = 0.002). IBD onset age was earlier in obese population (44.8 +/- 13.6 vs 35.6 +/- 15.6, P = 0.004). We did not detect any difference in disease extension. Obese subjects had consumed more frequently long course of systemic steroids (66.6% vs 12.5%, P = 0.02) as well as antibiotics such as metronidazole or ciprofloxacin (71.4% vs 54.7%, P = 0.05). No difference about other drugs (biologics, mesalazine or thiopurines) was observed. Disease activity was similar between obese and non obese subjects both for UC and CD. Obese IBD patients suffered more frequently from arterial hypertension, type 2 diabetes, non-alcoholic fatty liver disease. Regarding laboratory investigations, obese IBD patients had higher levels of triglyceridemia, fasting blood glucose, gamma-glutamyl-transpeptidase. On multivariate analysis, however, the only factor that appeared to be independently linked to obesity in IBD was the high abdominal circumference (OR = 16.3, 95%CI: 1.03-250, P = 0.04). CONCLUSION Obese IBD patients seem to have features similar to general obese population, and there is no disease-specific factor (disease activity, extension or therapy) that may foster obesity in IBD.