Functional Dyspepsia (FD) is a functional bowel disorder with significant global prevalence and contributes up to one third of gastroenterology outpatient appointments. It profoundly affects health-related quality of life likely due to its chronic nature and the co-existence of gastrointestinal (GI) and extra-intestinal symptoms. Currently, the gold standard for the diagnosis of FD is the Rome IV criteria. Rome IV subdivides FD into two sub groups, dependent on whether the symptoms are meal-related, the post prandial distress syndrome, or not, the epigastric pan syndrome. Currently, there are no reliable biomarkers to aid in the diagnosis of FD.

Current pathophysiological mechanisms implicated in the pathogenesis of FD include altered motility especially impaired accommodation and gastric emptying, visceral hypersensitivity, low-grade mucosal inflammation, dysbiosis of the gut microbiota, and abnormal central pain processing. There appears to be a degree of overlap with the mechanisms that are implicated in the pathogenesis of IBS. Furthermore, subjects with FD also have prominent “gas” related symptoms including bloating, belching, and distension. Subjects with FD also experience epigastric/abdominal pain and discomfort, and, in the prandial dis- tress syndrome sub-group, these symptoms are exclusively meal- related. This has led to researchers involved in FGID research to question whether FD and IBS are in fact two separate but related diseases, or simply one disease process with varying phenotypes

An incomplete understanding of the pathophysiology of IBS and its phenotypic heterogeneity has led to symptom-directed treatment approaches including PPI, prokinetics and anti-psychotics. However, less than one third of patients are satisfied with their current treatments. Dietary restriction of fermentable carbohydrates (low FODMAP diet) is now widely used in the management of IBS. These carbohydrates increase small intestinal water and colonic gas. Their dietary restriction has been investigated in few trials with up to 70% of patients reporting symptomatic benefit.  However there is not even a single randomized study evaluating the effect of low FODMAP diet in FD patients, which motivated us to conduct this study.