Dietary Treatment of Endometriosis-related Irritable Bowel Syndrome

Inclusion Criteria: * Signed informed consent * Age 18-50 years * Fluid spoken and written Danish * Diagnosed endometriosis (laparoscopy and/or MR-scan) at least one year ago and sufficient treated regarding medicine and surgery. Participant will be asked to bring a copy of their medical record from the hospital or from www.sundhed.dk to verify the diagnosis. * Diagnosis of irritable bowel syndrome according to the Rome III criteria. Both previous diagnosis and undiagnosed patients are included, as long as the study group evaluates that the patient meets the Rome III criteria. * Accept to follow a controlled exclusion diet for all meals for four weeks with only few accepted deviations from the diet. Exclusion Criteria: * Premature menopause * Organic bowel disease (Celiac disease, IBD, bowel endometriosis, malignant disease) * New therapeutic interventions during study period (medical/lifestyle/psychological). Already ongoing treatment is accepted. * Psychiatric disorder, psychotropic drugs * Patients, who the dietician accesses are familiar with low FODMAP diet and therefore is able to identify the placebo diet * Patients with complicated dietary needs, e.g. severe allergies or intolerances (including lactose and fructose intolerance), athletes, any type of vegetarianism or metabolic diseases * Pregnancy or planned pregnancy during the study period