The objective of the current study is to evaluate the effect of a probiotic mixture on the adequate relief and faecal microbiota in obese patients with irritable bowel syndrome

• The treatment period will last 8 weeks and after the treatment period, patients will be followed-up for another 2 weeks. Thus the overall trial period is the 10-week study period and end of 10th week is the end of the trial.
• Planned visits to gastroenterologists are at the screening period (-1 week), randomization period (0 weeks), and at the end of the treatment period (8th week).
• Patients will be instructed that unplanned visits to gastroenterologist are allowed only in case of a need or an urgency [e.g., adverse reactions, clinical deterioration and/or need for additional irritable bowel syndrome (IBS) management]. Unplanned visits will be recorded and does not exclude patients from the trial.
• For assessing other needed parameters (e.g., adequate relief, adverse reactions, irritable bowel syndrome (IBS) management) patients will be assessed by a physician, using an interactive voice response by telephone.
• Laboratory tests will be performed by certified clinical laboratories. Blood samples will be obtained by experienced trial nurses at the time of randomization (0 weeks).
• Anthropometric measurements will be assessed at the baseline and at the end of the treatment period (8th week).
• Irritable bowel syndrome (IBS) management (non-medication and medication therapy) will be assessed at the baseline, during the trial at the planned and unplanned visits to gastroenterologists, and at the end of the trial (by a physician using an interactive voice response by telephone). In a case of clinical deterioration IBS management is allowed during the trial and each will be recorded by gastroenterologists.
• Participants will receive 112 powder portion bags at the beginning of the trial and will be instructed to return the container after the 8-week treatment period. Leftover powder portion bags will be counted at the end of the treatment period (8th week) to estimate compliance. Compliant is considered a participant where no leftover powder portion bags will be recorded. Otherwise, the participant is considered non-compliant.
• Safety will be ensured by following adverse reactions during the trial. Scheduled assessment of adverse reactions is at the time of randomization, after 4 weeks, 8 weeks, and at the end of the trial. Responses will be recorded by a physician, at the planned visit of gastroenterologists and/or using an interactive voice response by telephone. Unscheduled recording of adverse reactions is during the entire trial by patients which will be instructed at the randomization period to report any adverse reactions to gastroenterologists using an interactive voice response by telephone. In a case of severe adverse reactions patients will be withdrawn from the trial and if needed. In case of a need or urgency (e.g., adverse reactions, clinical deterioration) clinical management will be provided in line with the best medical practice, by gastroenterologists and/or medical specialists depending on a medical condition.
• Patients can withdrawal from the trial any time. During the trial period withdrawal and its reason will be assessed by gastroenterologists at the visits or using an interactive voice response by telephone. Patients will be instructed in a case of a withdrawal to inform gastroenterologists and report the reason. In a lack of response the reason will be considered as other.

Inclusion Criteria:

• Obese [Body mass index (BMI) ≥30] men or women with confirmed IBS (all subtypes based on Rome IV Diagnostic Criteria for IBS) aged between 18 and 65 years.
• Written informed consent.

Exclusion Criteria:

• Pregnancy or lactation
• Severe systemic illness [cancer, gastrointestinal illness (e.g., colitis, Crohn's disease, celiac disease, recurrent diverticulitis), chronic renal failure, an endocrine disorder, metabolic disorder, angina, congestive heart failure, uncontrolled hypertension] or severely impaired general health
• Organic abnormality which is excluded by full blood count, C-reactive protein or erythrocyte sedimentation rate, and thyroid-stimulating hormone for constipated IBS participants. To exclude other organic lower gastrointestinal disease faecal calprotectin will be checked, and celiac test and colonoscopy will be performed if needed.
• Previous abdominal surgery except for appendectomy, cholecystectomy and abdominal wall hernia repair
• History of psychiatric disorder
• History of participation in another clinical trial within 3 months before the onset of this trial
• Medications that could affect the outcomes: oral steroid, sulfasalazine, cholestyramine, misoprostol and probiotics usage 3 months prior to and during the study; and antacids with magnesium or aluminium usage during the study

We will share all necessary documents which are not under GDPR protection

after enrollment, 50% of patients and will be available 6 months after study termination

Patients, Ethic committee members, regulatory organisations