The Clinical Impact of Obesity in Patients With Disorders of Defecation: A Cross-Sectional Study of 1,155 Patients

Am J Gastroenterol. 2023 Aug 18. doi: 10.14309/ajg.0000000000002400. Online ahead of print.


Pam Chaichanavichkij 1Paul F Vollebregt 1Karekin Keshishian 2Charles H Knowles 1S Mark Scott 1


Author information

1National Bowel Research Centre and GI Physiology Unit, Blizard Institute, Centre for Neuroscience, Surgery & Trauma, Queen Mary University of London, London, United Kingdom.

2Department of Colorectal Surgery, The Royal London Hospital, Whitechapel Road, London, United Kingdom.


Introduction: Obesity is a global epidemic. Its clinical impact on symptoms of fecal incontinence (FI) and/or constipation and underlying anorectal pathophysiology remains uncertain.

Methods: This is a cross-sectional study of consecutive patients meeting Rome IV criteria for FI and/or functional constipation, with data on body mass index (BMI), attending a tertiary center for investigation between 2017 and 2021. Clinical history, symptoms, and anorectal physiologic test results were analyzed according to BMI categories.

Results: A total of 1,155 patients (84% female) were included in the analysis (33.5% normal BMI; 34.8% overweight; and 31.7% obese). Obese patients had higher odds of FI to liquid stools (69.9 vs 47.8%, odds ratio [OR] 1.96 [confidence interval: 1.43-2.70]), use of containment products (54.6% vs 32.6%, OR 1.81 [1.31-2.51]), fecal urgency (74.6% vs 60.7%, OR 1.54 [1.11-2.14]), urge FI (63.4% vs 47.3%, OR 1.68 [1.23-2.29]), and vaginal digitation (18.0% vs 9.7%, OR 2.18 [1.26-3.86]). A higher proportion of obese patients had Rome criteria-based FI or coexistent FI and functional constipation (37.3%, 50.3%) compared with overweight patients (33.8%, 44.8%) and patients with normal BMI (28.9%, 41.1%). There was a positive linear association between BMI and anal resting pressure (β 0.45, R 2 0.25, P = 0.0003), although the odds of anal hypertension were not significantly higher after Benjamini-Hochberg correction. Obese patients more often had a large clinically significant rectocele (34.4% vs 20.6%, OR 2.62 [1.51-4.55]) compared with patients with normal BMI.

Discussion: Obesity affects specific defecatory (mainly FI) and prolapse symptoms and pathophysiologic findings (higher anal resting pressure and significant rectocele). Prospective studies are required to determine whether obesity is a modifiable risk factor of FI and constipation.

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