According to a study by the Inflammatory Bowel Disease Research Group, severe obesity is a risk factor for developing Crohn’s disease and ulcerative colitis
A study led by the CIBEREHD group on inflammatory bowel diseases at Germans Trias has concluded, for the first time, that severe obesity is a risk factor for developing one of the main types of inflammatory bowel disease (IBD): Crohn's disease or ulcerative colitis. These conditions are estimated to affect 1% of the population in Catalonia and are recognised each year on 19 May as part of World IBD Day.
The study, published in the Journal of Crohn's and Colitis, is based on the analysis of a large database of over one million individuals registered by the Catalan Health Service between 2005 and 2020. Specifically, the study analysed data from one million people with obesity, nearly 100,000 with severe obesity, and around 15,000 who had undergone bariatric surgery. One of the study's main strengths is its use of a large and representative population cohort, with long-term follow-up and information on factors that could influence the link between obesity and the development of IBD.
Although the causes and pathophysiology of IBD are not fully understood, it is known that they result from a complex interaction between genetic and environmental factors, changes in the gut microbiota, defects in the intestinal barrier, and altered immune regulation. Among environmental factors, smoking has been clearly and consistently associated with an increased risk of developing Crohn's disease or ulcerative colitis.
However, research is ongoing into other factors that may contribute to the development of these conditions and influence their progression or response to treatment. One such factor is obesity, which is now the focus of growing clinical interest as a possible cause in the onset of IBD.
Higher incidence among those with severe obesity
Eugeni Domènech, Head of the Digestive Diseases Department at Germans Trias, Principal Investigator of the Inflammatory Bowel Disease Research Group (GReMII) at IGTP, and member of the CIBEREHD group, concludes that individuals with severe obesity and those who had undergone bariatric surgery were at a higher risk of developing IBD compared to individuals with obesity.
Specifically, the incidence rate of IBD among people with severe obesity and no history of bariatric surgery was 0.9 cases per 1,000 person-years; among those who had undergone surgery before being diagnosed with IBD, the rate was 0.84; by contrast, the rate among individuals with obesity was 0.60.
Therefore, "severe obesity and bariatric surgery are independent risk factors for developing IBD, in addition to smoking," stresses Domènech, who adds that this risk is closely linked to severe obesity. According to the study, alterations in the microbiome and a pro-inflammatory state associated with obesity should be considered possible triggers for IBD in genetically predisposed individuals.
Furthermore, Domènech notes that this association between obesity and IBD "opens the door to considering the relevance of non-invasive screening for IBD in this population group". The study highlights existing evidence suggesting a long inactive or preclinical phase of IBD, during which immunological changes gradually occur. This is supported by the presence of inflammatory biomarkers and microbial antibodies many years before clinical symptoms emerge. Such screening could involve repeated measurements of faecal calprotectin, a protein easily detected in stool samples. According to recent research by the same group, this test helps reduce the number of colonoscopies and improves patient monitoring in Crohn's disease.
Crohn's disease and ulcerative colitis are the most common inflammatory bowel diseases-chronic inflammatory disorders of unknown origin affecting the gastrointestinal tract. Common symptoms include diarrhoea, blood in stools, fatigue, abdominal pain, loss of appetite and weight, and fever. Around 1% of the Catalan population lives with one of these conditions, with Crohn's disease accounting for about half of the cases. Each year, Germans Trias follows up around 2,000 patients with Crohn's disease or ulcerative colitis.
Reference
Fiorella Cañete, Emili Vela, Margalida Calafat, Jordi Piera, Míriam Mañosa, Eugeni Domènech, Severe obesity, a susceptibility factor for developing inflammatory bowel disease: results of a population-based study. Journal of Crohn's and Colitis, Volume 19, Issue 2, February 2025, jjaf010, DOI: https://doi.org/10.1093/ecco-jcc/jjaf010