The Association Of Obesity With Irritable Bowel Syndrome In Adults: A Systematic Review

Abstract

The relationship between obesity and Irritable Bowel Syndrome (IBS) remains a subject of ongoing debate, as epidemiological evidence has yielded inconsistent findings. Although both conditions are highly prevalent and significantly impair quality of life, a universal association between them has not been established. This systematic review aims to synthesize the available evidence and clarify the nature of this relationship by examining specific clinical phenotypes, diagnostic criteria, and underlying biological mechanisms. Following the PRISMA 2020 guidelines, a comprehensive search was performed across multiple databases. Eligible studies included adult populations, used standardized measures of obesity such as Body Mass Index (BMI) or waist circumference, and diagnosed IBS using the Rome criteria or physician assessment. Thirteen studies—including systematic reviews, meta-analyses, observational studies, and clinical trials—met the inclusion criteria and were incorporated into a narrative synthesis. The findings indicate no consistent overall association between BMI-defined obesity and IBS prevalence. However, significant associations were observed in specific subgroups. A Mendelian randomization study demonstrated strong genetic evidence supporting a causal link between visceral adiposity and IBS risk. Additional studies identified significant relationships for the diarrhea-predominant subtype (IBS-D) and for IBS diagnosed using Rome IV criteria. Interventional studies further showed that reductions in abdominal fat were associated with clinically meaningful improvements in IBS symptoms and quality of life. Overall, the evidence suggests that the most relevant association is not with general obesity but specifically with metabolically active visceral adiposity. These findings support incorporating targeted weight-management strategies into the clinical approach for patients with coexisting obesity and IBS.