Journal of Gastroenterology and HepatologyVolume 38, Issue 3 p. 344-345 EditorialFree Access Obesity and functional gastrointestinal disorders: What is the link? Sanjiv Mahadeva MD, MRCP, Sanjiv Mahadeva MD, MRCP Division of Gastroenterology, Department of Medicine, University of Malaya, Kuala Lumpur, MalaysiaSearch for more papers by this author Sanjiv Mahadeva MD, MRCP, Sanjiv Mahadeva MD, MRCP Division of Gastroenterology, Department of Medicine, University of Malaya, Kuala Lumpur, MalaysiaSearch for more papers by this author First published: 10 March 2023 https://doi.org/10.1111/jgh.16158AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Functional gastrointestinal disorders (FGIDs), or disorders of gut-brain interaction (DGBI), are one of the most common GI disorders globally, with an estimated prevalence of almost 40% globally.1 Although there are some 33 disorders that make up FGIDs, the most prevalent conditions include functional dyspepsia (FD), irritable bowel syndrome (IBS), and functional constipation (FC). The pathophysiology of FGIDs is complex, involving gut-brain axis dysregulation, visceral hypersensitivity, gastrointestinal dysmotility, low grade intestinal inflammation, gut dysbiosis, and psychological disorders.2 They are one of the most common conditions managed in gastroenterology clinics and often lead to increased healthcare utilization.3 Epidemiologically, several factors have been shown to be associated with FGIDs including gender, age, ethnicity, genetics, geographical location and diet.4 Obesity, defined as a body mass index (BMI) of > 30 kg/m2, is yet another factor that has been linked with FGIDs. In a population-based study, Guo et al. found that IBS was significantly related to the metabolic syndrome and elevated triglycerides among 1096 Japanese subjects.5 In a recent systematic review of 348 studies, Zia et al. found that obesity (in addition to gender, psychological disorders, stress, poor sleep, and somatic symptoms) was identified as a risk factor for IBS and abdominal pain-related DGBI.6 Furthermore, some studies have reported that chronic GI symptoms (which may include FGIDs) among morbidly obese patients do improve after undergoing weight-loss surgery.7 So how does obesity cause FGIDs? In this issue of the journal, Yanping et al. postulate that obesity may lead to FGIDS, particularly IBS, by increasing visceral hypersensitivity.8 Visceral hypersensitivity is one of the pathophysiological mechanisms involved in generating symptoms in IBS, mainly by having a lower pain threshold to bowel distension or an increased sensitivity to normal intestinal function.2 The authors suggest that obesity may be involved in hyperexcitability of primary visceral afferent fibers at the intestinal level and enhanced perception of the intestinal signal in the brain. Through low-grade, chronic inflammation, obesity is thought to mediate the effects of sensitizing the gut via an increased intestinal permeability, gut microbiota variation, and vitamin D insufficiency. Although the hypothesis suggested by Wu et al. are plausible, there are some inconsistencies in the association of obesity or an increased BMI with FGIDs. In a large European population-based study exploring BMI with various FGIDs among 35 447 adults, FD was associated with being underweight while the risk of functional diarrhea increased with BMI in females. Other associations were insignificant.9 This observation was similarly observed in a primary care study of 1002 Asian adults, whereby a low BMI (< 18 kg/m2) and anxiety were found to be associated with FD, while no other FGIDs were associated with BMI.10 Hence, since obesity seems to be associated with some FGIDs (IBS in particular) and not others, it is uncertain if the causal mechanism is via visceral hypersensitivity alone. Another possibility, as the authors suggest, is that it is not an increased BMI per se but abdominal/visceral adiposity that leads to FGIDs via chronic low-grade inflammation and its sequelae.11 Both obesity and FGIDs share certain similar pathophysiological mechanisms, such as chronic low-grade inflammation, changes in intestinal permeability, endocrine abnormalities, and an altered gut microbiome.2, 12 However, cause and effect between obesity and FGIDs cannot be easily disentangled. Further studies exploring pathophysiological mechanisms between different FGIDs and abdominal/visceral adiposity are still required, before the link can be confidently ascertained. References 1Sperber AD, Bangdiwala SI, Drossman DA et al. Worldwide Prevalence and Burden of Functional Gastrointestinal Disorders, Results of Rome Foundation Global Study. Gastroenterology 2021; 160: 99– 114 e3. 2Black CJ, Drossman DA, Talley NJ, Ruddy J, Ford AC. Functional gastrointestinal disorders: advances in understanding and management. Lancet 2020; 396: 1664– 1674. 3Chuah KH, Cheong SY, Lim SZ, Mahadeva S. Functional dyspepsia leads to more healthcare utilization in secondary care compared with other functional gastrointestinal disorders. J. Dig. Dis. 2022; 23: 111– 117. 4Oshima T, Miwa H. Epidemiology of functional gastrointestinal disorders in Japan and in the world. J. Neurogastroenterol. Motil. 2015; 21: 320–329. 5Guo Y, Niu K, Momma H et al. Irritable bowel syndrome is positively related to metabolic syndrome: a population-based cross-sectional study. PLoS ONE 2014; 9: e112289. 6Zia JK, Lenhart A, Yang PL et al. Risk Factors for Abdominal Pain-Related Disorders of Gut-Brain Interaction in Adults and Children: A Systematic Review. Gastroenterology 2022; 163: 995– 1023 e3. 7Clements RH, Gonzalez QH, Foster A, Richards WO, McDowell J, Bondora A, Laws HL. Gastrointestinal symptoms are more intense in morbidly obese patients and are improved with laparoscopic Roux-en-Y gastric bypass. Obes. Surg. 2003; 13: 610– 614. 8Yanping W, Gao X, Cheng Y et al. The interaction between obesity and visceral hypersensitivity. J. Gastroenterol. Hepatol. 2023; 38: 370– 377. 9Le Pluart D, Sabaté JM, Bouchoucha M, Hercberg S, Benamouzig R, Julia C. Functional gastrointestinal disorders in 35 447 adults and their association with body mass index. Aliment. Pharmacol. Ther. 2015; 41: 758– 767. 10Beh KH, Chuah KH, Rappek NAM, Mahadeva S. The association of body mass index with functional dyspepsia is independent of psychological morbidity: A cross-sectional study. PLoS ONE 2021; 16: e0245511. https://doi.org/10.1371/journal.pone.024551 11Lee CG, Lee JK, Kang YS et al. Visceral abdominal obesity is associated with an increased risk of irritable bowel syndrome. Am. J. Gastroenterol. 2015; 110: 310– 319. 12Kawai T, Autieri MV, Scalia R. Adipose tissue inflammation and metabolic dysfunction in obesity. Am. J. Physiol. Cell Physiol. 2021; 320: C375– C391. Volume38, Issue3March 2023Pages 344-345 ReferencesRelatedInformation