Exclude or Expose in Irritable Bowel Syndrome: What Works for Whom and How?

April 29, 2026 updated by: University of Melbourne

Exclude or Expose in Irritable Bowel Syndrome: What Works for Whom, and How? A Randomized Controlled Trial of Internet-Delivered FODMAP Diet Versus Exposure-Based Cognitive Behavioral Therapy

This research project will assess how two treatments for irritable bowel syndrome (one dietary and one behavioral) work and for whom. This will be done by assessing moderators (what treatment works for who and in what context) and mediators (how treatment works). Investigators will also assess how the diet and behavioral treatments affect IBS symptoms during treatment. Participants will be randomized to either: i. A FODMAP diet online program that focuses on modifying the consumption of foods high or moderate in fermentable carbohydrates (FODMAPS) to manage IBS symptoms. or, ii. An Exposure-based Cognitive Behavioral Therapy (E-CBT) online program for IBS that focuses on changing symptom-related behaviors which are known to worsen IBS symptoms.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

This research uses a randomized controlled trial to investigate the treatment of irritable bowel syndrome (IBS). A range of treatments for IBS are available, but each work for only a portion of patients, and it is unclear why. This research project will assess how two treatments (one dietary and one behavioral) work and for whom. Investigators will do this by assessing moderators (what treatment works for who and in what context) and mediators (how treatment works). This project will also assess how the diet and behavioral treatments affect IBS symptoms during treatment. Participants will be randomized to either: i. A FODMAP diet online program that focuses on modifying the consumption of foods high or moderate in fermentable carbohydrates (FODMAPS) to manage IBS symptoms. This treatment involves 3-phases: FODMAP restriction (phase 1), FODMAP re-introduction (phase 2), and FODMAP personalization (phase 3), or, ii. An Exposure-based Cognitive Behavioral Therapy (E-CBT) online program for IBS that focuses on symptom-related behaviors such as avoidance of activities and foods, excessive toilet visits, and behaviors to control symptoms which are known to worsen IBS symptoms. E-CBT uses daily self-observation and exposure exercises to change these behaviors to relieve IBS symptoms. Investigators believe that both treatments, FODMAP diet and E-CBT, will lead to an improvement in IBS gastrointestinal symptoms. Primary moderators and mediators to be assessed include gastrointestinal symptom anxiety, food avoidance behaviour and FODMAP intake.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
235

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Contact Backup

Study Locations

  • Australia
    • Victoria
      • Melbourne, Victoria, Australia, 3010
        • Recruiting
        • University of Melbourne
        • Contact:
          • Jessica Biesiekierski

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria: Each participant must meet all of the following criteria to be enrolled in this trial:

  • Living in Australia or the United States
  • Aged 18 years or older
  • Body Mass Index (BMI) [Equation]18.5kg/m2 and [Equation] 34.9kg/m2
  • Diagnosed with IBS by a General Practitioner, Family Physician, or Gastroenterologist, or Advanced Specialist Dietitian
  • Currently fulfill Rome IV criteria for IBS
  • Symptomatic at the time of recruitment (IBS-SSS > 175)
  • Access to a computer and internet
  • Sufficient English language and computer skills to complete a text-based online treatment
  • Willing to make dietary or behavioral changes in line with the allocated treatment program
  • Ability to provide informed consent

Exclusion Criteria:Patients meeting any of the following criteria will be excluded from the trial:

  • Presence or known history of other GI disease (e.g. coeliac disease, Inflammatory Bowel Disease) or history of gastrointestinal cancer
  • History of major gastrointestinal surgery (not appendectomy, cholecystectomy or hemorrhoidectomy)
  • Individuals who report alarm symptoms (e.g., blood in stool, recent unexplained/unintentional weight loss >5% body weight, a recent change in bowel habits if >50 years, family history of gastrointestinal cancer or gastrointestinal diseases, large volumes of diarrhea occurring at night, fever associated with gut symptoms, recurrent vomiting, persistent unexplained iron deficiency) will be excluded if appropriate medical investigations have not been conducted, unless written medical approval is provided from a general practitioner, family physical, or gastroenterologist.
  • Diagnosis of major disease that could explain current gastrointestinal symptoms such as severe diabetic, cardiac, liver, neurological, neuropathy disease
  • History or current diagnosis of psychotic disorder or bipolar disorder
  • Current diagnosis of substance abuse disorder or major depressive disorder or active suicidal ideation
  • History or current diagnosis of an eating disorder
  • Current enteral/parenteral feeding or use of supplemental feeds (e.g. Ensure)
  • Pregnant or lactating or planning to become pregnant during the 12-week intervention period
  • Commenced or change in dose of antibiotics and medications that potentially affect the gastrointestinal transit (e.g. anti-diarrheals and laxatives) in the 3 months preceding study commencement.
  • Commenced taking or changed dose of probiotics, prebiotics, fibre supplements and digestive enzymes in the 3 months preceding study commencement
  • Commenced or change dose in psychotropic medication in the 3 months preceding study commencement
  • Are currently undertaking behavioral therapy for IBS (including cognitive behavioral therapy, CBT), or have undertaken clinician-delivered behavioral therapy for the treatment of IBS
  • Are currently undertaking or have undertaken a dietitian-prescribed and delivered restrictive diet for IBS (e.g., FODMAP diet).

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: FODMAP Diet
Fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) Diet is a 12-week online intervention with dietitian support.
Other: FODMAP Diet
The intervention is an online diet program. The diet is the low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet. It is a 3-phase diet which involves: 1.Phase 1 FODMAP restriction: restrict foods high or moderate in FODMAPs and swap these for low FODMAP alternatives; 2. Phase 2 FODMAP reintroduction: continue to follow a low FODMAP diet and complete a series of food challenges to understand which foods and FODMAPs are tolerated and which trigger symptoms; 3. Phase 3 FODMAP personalization: include well-tolerated foods and FODMAPs back into the diet, and restrict poorly tolerated foods and FODMAPs to a level needed to maintain symptom relief. The online FODMAP program is a self-directed diet program with support from an online clinician (Accredited Practicing Dietitian [APD]). The content is delivered over 12 weeks. After each module participants will complete homework activities and questions and submit them to the dietitian for feedback.
Experimental: Exposure-based Cognitive Behavioral Therapy (E-CBT)
Exposure-based Cognitive Behavioral Therapy is a 12-week online intervention with psychologist support.
Behavioral: Exposure-based Cognitive Behavioral Therapy
The intervention is an online behavioral therapy program. The behavioral therapy is Exposure-based Cognitive Behavioral Therapy (E-CBT) Program. The E-CBT program is organised into six steps to be completed over 12 weekly modules with support from an online clinician (Psychologist). The first step contains a rationale for the treatment and instructions on self-observation. Steps 2, 3 and 4 contain a presentation of a psychological model of IBS and continued self-observation exercises. The fifth step covers exposure exercises, divided into three categories; (1) exercises that provoke symptoms, (2) abolishment of behaviors that serve to control symptoms, (3) exposure to situations where symptoms were unwanted. The final step (Step 6) includes how to handle relapses into avoidance behaviors and how to maintain a widened behavioral repertoire. After each module participants will be directed to complete homework activities and questions and submit them to the psychologist for feedback.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Gastrointestinal Symptom Rating Scale-Irritable Bowel Syndrome (GSRS-IBS )
Time Frame: Measured weekly between baseline (prior to intervention) and after intervention completed (week 12).
The GSRS-IBS is a 13-item measure of IBS symptom severity to reflect the last 7 days. The items are scored between 1 (no discomfort at all) and 7 (very severe discomfort), rendering a total score between 13 and 91.
Measured weekly between baseline (prior to intervention) and after intervention completed (week 12).

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Change from baseline in Gastrointestinal Symptom Rating Scale-Irritable Bowel Syndrome (GSRS-IBS)
Time Frame: Baseline and 3-and 6 month follow up time points after intervention completed (week 12).
The GSRS-IBS is a 13-item measure of IBS symptom severity to reflect the last 7 days. The items are scored between 1 (no discomfort at all) and 7 (very severe discomfort), rendering a total score between 13 and 91.
Baseline and 3-and 6 month follow up time points after intervention completed (week 12).
Change from baseline in Irritable Bowel Syndrome - Symptom Severity Score (IBS-SSS) questionnaire
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
The IBS-SSS is a 5-item measure of the severity of IBS symptoms: frequency and severity of abdominal pain, severity of bloating, dissatisfaction with bowel habits and impact on life in general. Questions ask about IBS and gut symptoms during the past 7 days except question 4 which asks participants to enter the number of days they get pain in every 10. days. A total score ranging from 0 to 500. Mild, moderate and severe cases are indicated by scores of 75 to <175, 175 to <300 and >300 respectively
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in IBS quality of life (IBS-QOL) questionnaire
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
IBS-QOL is used to assess the impact on quality of life for patients with IBS and consists of 34 items scored between 1 and 5, resulting in a maximum score of 170.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in Nine Item ARFID (Avoidant Restrictive Food Intake Disorder) Screen (NIAS) questionnaire
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
NIAS is a 9-item measure of ARFID symptoms. The scale has 9 questions, scored from 0 (strongly disagree) to 5 (strongly agree) and summed into three subscales (fear of adverse consequences, lack of interest/appetite, and sensory sensitivity); each range = 0-15), with higher scores indicating greater severity.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in Fear of Food Questionnaire (FFQ) questionnaire
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
The Fear of Food Questionnaire (FFQ) is an 18-item measure of food-related fears averaged into five subscales (GI fears, food fears, food avoidance, social impairment, and distress/loss of pleasure) and a total score between 0 and 90 (each range = 0-5), with higher scores indicating greater food related fears.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in Patient Health Questionnaire-12 (PHQ-12) (derived from PHQ-15) questionnaire
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
PHQ-15 is a validated measure of somatization. Questions reflect the previous 4 weeks. It comprises 15 somatic symptoms with each symptom scored from 0 ("not bothered at all") to 2 ("bothered a lot"). The PHQ-15 will be administered to facilitate assessment of PHQ-12. The PHQ-12 is a commonly used modification of the PHQ-15 without three GI-related items; constipation, loose bowels, or diarrhea; nausea, gas, or indigestion. The PHQ-12 represents non-GI or extraintestinal somatic symptoms.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in Generalized anxiety disorder (GAD-7) questionnaire
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
GAD-7 is a 7-item questionnaire used for screening and measuring the severity of anxiety symptoms. Questions reflect the previous 14 days and responses are measured on a 4-point Likert scale; 0=not at all sure; 1=several days; 2=more than half the days; 3=nearly every day. Total GAD-7 scores range from 0-21 with higher scores indicating greater severity of symptoms.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in Patient Health Questionnaire (PHQ-9) questionnaire
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
The Patient Health Questionnaire (PHQ-9) is a 9-item measure of depression severity. Questions reflect the previous 14 days. Each of the 9 items can be scored from 0 (not at all) to 3 (nearly every day) and severity score can range from 0 to 27. PHQ-9 scores of 5, 10, 15, and 20 indicate mild, moderate, moderately severe, and severe depression, respectively.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in Gastrointestinal Specific Anxiety (GSA) measured using Visceral Sensitivity Index (VSI)
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
The VSI is a 15-item measure of gastrointestinal-specific anxiety, scored on a Likert scale of 1 to 6 with 1=strongly agree; 2=moderately agree; 3=mildly agree; 4=mildly disagree; 5=moderately disagree and 6=strongly disagree.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in Avoidance behavior measured using Irritable Bowel Syndrome-Behavioural Responses Questionnaire (IBS-BRQ)
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
IBS-BRQ is a 26-item measure of avoidance behavior. The scale has 26 items, scored from 1 (never) to 7 (always), indicating how persistently the particular avoidance or toilet behavior is carried out.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in Total FODMAP intake measured using 3-day food diary
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Participants will record their food intake for 3 days (including one weekend day) using paper or an app. Total FODMAP intake will be calculated g/day.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Change from baseline in stool frequency and consistency using 7-day stool diary based on Bristol Stool Form Scale (BSFS)
Time Frame: Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
The stool diary will be completed over 7 days and is based on the Bristol Stool Form Scale (BSFS) for IBS subtyping and bowel habit assessment i.e. stool frequency and consistency. Stool consistency will be quantified according to ROME classifications.
Baseline, after intervention completed (week 12), and at follow up time points of 3-and 6 months following the 12-week intervention.
Gastrointestinal microbiome composition and function using stool sample using OMNIgene GUT
Time Frame: Gastrointestinal microbiome composition and function will be measured 2nd weekly between baseline (prior to intervention) and after intervention completed (week 12) as exploratory mediators.
Gut microbiome composition (i.e., alpha diversity, beta diversity, relative abundance) and function 16S rRNA and shotgun sequencing. Measured as exploratory mediators.
Gastrointestinal microbiome composition and function will be measured 2nd weekly between baseline (prior to intervention) and after intervention completed (week 12) as exploratory mediators.
Individual FODMAPs' intake using 3-day food diary
Time Frame: Will be measured 2nd weekly between baseline (prior to intervention) and after intervention completed (week 12) as exploratory mediators.
Participants will record their food intake for 3 days (including one weekend day) using paper or an app. Individual FODMAPs' intake will be calculated g/day. Measured as exploratory mediators.
Will be measured 2nd weekly between baseline (prior to intervention) and after intervention completed (week 12) as exploratory mediators.
Gastrointestinal Symptom Rating Scale-Irritable Bowel Syndrome GSRS-IBS
Time Frame: Baseline (prior to start of intervention) as an exploratory moderator.
The GSRS-IBS is a 13-item measure of IBS symptom severity to reflect the last 7 days. The items are scored between 1 (no discomfort at all) and 7 (very severe discomfort), rendering a total score between 13 and 91. Measured as an exploratory moderator.
Baseline (prior to start of intervention) as an exploratory moderator.
IBS quality of life (IBS-QOL) questionnaire
Time Frame: Baseline (prior to start of intervention) as an exploratory moderator.
Description: I IBS-QOL is used to assess the impact on quality of life for patients with IBS and consists of 34 items scored between 1 and 5, resulting in a maximum score of 170. Measured as an exploratory moderator.
Baseline (prior to start of intervention) as an exploratory moderator.
Fear of Food Questionnaire (FFQ) questionnaire
Time Frame: Baseline (prior to start of intervention) as an exploratory moderator.
The Fear of Food Questionnaire (FFQ) is an 18-item measure of food-related fears averaged into five subscales (GI fears, food fears, food avoidance, social impairment, and distress/loss of pleasure) and a total score between 0 and 90 (each range = 0-5), with higher scores indicating greater food related fears. Measured as an exploratory moderator.
Baseline (prior to start of intervention) as an exploratory moderator.
Nine Item ARFID (Avoidant Restrictive Food Intake Disorder) Screen (NIAS) questionnaire
Time Frame: Baseline (prior to start of intervention) as an exploratory moderator.
NIAS is a 9-item measure of ARFID symptoms. The scale has 9 questions, scored from 0 (strongly disagree) to 5 (strongly agree) and summed into three subscales (fear of adverse consequences, lack of interest/appetite, and sensory sensitivity); each range = 0-15), with higher scores indicating greater severity. Measured as an exploratory moderator.
Baseline (prior to start of intervention) as an exploratory moderator.
Patient Health Questionnaire-12 (PHQ-12) (derived from PHQ-15) questionnaire
Time Frame: Baseline (prior to start of intervention) as an exploratory moderator.
PHQ-15 is a validated measure of somatization. Questions reflect the previous 4 weeks. It comprises 15 somatic symptoms with each symptom scored from 0 ("not bothered at all") to 2 ("bothered a lot"). The PHQ-15 will be administered to facilitate assessment of PHQ-12. The PHQ-12 is a commonly used modification of the PHQ-15 without three GI-related items; constipation, loose bowels, or diarrhea; nausea, gas, or indigestion. The PHQ-12 represents non-GI or extraintestinal somatic symptoms. Measured as an exploratory moderator.
Baseline (prior to start of intervention) as an exploratory moderator.
Patient Health Questionnaire (PHQ-9) questionnaire
Time Frame: Baseline (prior to start of intervention) as an exploratory moderator.
The Patient Health Questionnaire (PHQ-9) is a 9-item measure of depression severity. Questions reflect the previous 14 days. Each of the 9 items can be scored from 0 (not at all) to 3 (nearly every day) and severity score can range from 0 to 27. PHQ-9 scores of 5, 10, 15, and 20 indicate mild, moderate, moderately severe, and severe depression, respectively. Measured as an exploratory moderator.
Baseline (prior to start of intervention) as an exploratory moderator.
Generalized anxiety disorder (GAD-7) questionnaire
Time Frame: Baseline (prior to start of intervention) as an exploratory moderator.
GAD-7 is a 7-item questionnaire used for screening and measuring the severity of anxiety symptoms. Questions reflect the previous 14 days and responses are measured on a 4-point Likert scale; 0=not at all sure; 1=several days; 2=more than half the days; 3=nearly every day. Total GAD-7 scores range from 0-21 with higher scores indicating greater severity of symptoms. Measured as an exploratory moderator.
Baseline (prior to start of intervention) as an exploratory moderator.
Gastrointestinal microbiome composition and function using stool sample using a stool sample collection kit.
Time Frame: Baseline (prior to start of intervention) as an exploratory moderator.
Gut microbiome composition (i.e., alpha diversity, beta diversity, relative abundance) and function 16S rRNA and shotgun sequencing . Measured as an exploratory moderator.
Baseline (prior to start of intervention) as an exploratory moderator.
IBS subtype using 7-day stool diary based on Bristol Stool Form Scale (BSFS).
Time Frame: Baseline (prior to start of intervention) as an exploratory moderator.
The stool diary will be completed over 7 days and is based on the Bristol Stool Form Scale (BSFS) for IBS subtyping and bowel habit assessment i.e. stool frequency and consistency. Stool consistency will be quantified according to ROME classifications. Measured as a exploratory moderator.
Baseline (prior to start of intervention) as an exploratory moderator.
Client Satisfaction Questionnaire
Time Frame: End of the 12-week intervention and at 3-and 6 months follow up time points after 12-week intervention..
The Client Satisfaction Questionnaire is an 8-question brief global measure of client satisfaction. The eight questions are measured on a 4-point Likert scale with questions 1, 3, 6 and 7 measured on a positive scale and questions 2, 4, 5 and 8 on a negative scale. Total scores range from 8 to 32, with the higher number indicating greater satisfaction.
End of the 12-week intervention and at 3-and 6 months follow up time points after 12-week intervention..
Proportion of participants who achieve a change from baseline in Irritable Bowel Syndrome - Symptom Severity Score (IBS-SSS) of ≥50 points total score.
Time Frame: Baseline and after intervention completed (week 12)
The IBS-SSS is a 5-item measure of the severity of IBS symptoms: frequency and severity of abdominal pain, severity of bloating, dissatisfaction with bowel habits and impact on life in general. Questions ask about IBS and gut symptoms during the past 7 days with the exception of question 4 which asks participants to enter the number of days they get pain in every 10. days. A total score ranging from 0 to 500. Mild, moderate and severe cases are indicated by scores of 75 to <175, 175 to <300 and >300 respectively
Baseline and after intervention completed (week 12)
Proportion of participants who achieve a change from baseline in Gastrointestinal Symptom Rating Scale-Irritable Bowel Syndrome (GSRS-IBS) of ≥30% total score
Time Frame: Baseline and after intervention completed (week 12)
The GSRS-IBS is a 13-item measure of IBS symptom severity to reflect the last 7 days. The items are scored between 1 (no discomfort at all) and 7 (very severe discomfort), rendering a total score between 13 and 91.
Baseline and after intervention completed (week 12)

Other Outcome Measures

Other Outcome Measures

For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Gastrointestinal Specific Anxiety (GSA) measured using Visceral Sensitivity Index (VSI)
Time Frame: VSI will be measured 2nd weekly between baseline (prior to intervention), after intervention (week 12) and and at follow up timepoints of 3-and 6 months following the 12-week intervention as a putative mediator.
The VSI is a 15-item measure of gastrointestinal-specific anxiety, scored on a Likert scale of 1 to 6 with 1=strongly agree; 2=moderately agree; 3=mildly agree; 4=mildly disagree; 5=moderately disagree and 6=strongly disagree. The VSI is being measured as a putative mediator.
VSI will be measured 2nd weekly between baseline (prior to intervention), after intervention (week 12) and and at follow up timepoints of 3-and 6 months following the 12-week intervention as a putative mediator.
Avoidance behavior measured using Irritable Bowel Syndrome-Behavioural Responses Questionnaire (IBS-BRQ)
Time Frame: IBS-BRQ will be measured 2nd weekly between baseline (prior to intervention), after intervention (week 12) and and at follow up timepoints of 3-and 6 months following the 12-week intervention as a putative mediator.
IBS-BRQ is a 26-item measure of avoidance behavior. The scale has 26 items, scored from 1 (never) to 7 (always), indicating how persistently the particular avoidance or toilet behavior is carried out. IBS-BRQ is measured as a putative mediator.
IBS-BRQ will be measured 2nd weekly between baseline (prior to intervention), after intervention (week 12) and and at follow up timepoints of 3-and 6 months following the 12-week intervention as a putative mediator.
Total FODMAP intake measured using 3-day food diary
Time Frame: Total FODMAP intake will be measured 2nd weekly between baseline (prior to intervention), after intervention (week 12) and and at follow up timepoints of 3-and 6 months following the 12-week intervention as a putative mediator.
Participants will record their food intake for 3 days (including one weekend day) using paper or an app. Total FODMAP intake will be calculated g/day. Total FODMAP intake is being measured as a putative mediator.
Total FODMAP intake will be measured 2nd weekly between baseline (prior to intervention), after intervention (week 12) and and at follow up timepoints of 3-and 6 months following the 12-week intervention as a putative mediator.
Treatment preference
Time Frame: Baseline (prior to start of intervention) as a putative moderator.
Baseline treatment preference will be assessed with a single question prior to randomization: "If you had a choice, which treatment would you prefer to receive?". Three response options will be provided: FODMAP diet program; Cognitive Behavioral Therapy program; No preference. Measured as a putative moderator.
Baseline (prior to start of intervention) as a putative moderator.
Gastrointestinal Specific Anxiety (GSA) measured using Visceral Sensitivity Index (VSI)
Time Frame: Baseline (prior to start of intervention) as a putative moderator.
The VSI is a 15-item measure of gastrointestinal-specific anxiety, scored on a Likert scale of 1 to 6 with 1=strongly agree; 2=moderately agree; 3=mildly agree; 4=mildly disagree; 5=moderately disagree and 6=strongly disagree. The VSI is being measured as a putative moderator.
Baseline (prior to start of intervention) as a putative moderator.
Avoidance behavior measured using Irritable Bowel Syndrome-Behavioural Responses Questionnaire (IBS-BRQ)
Time Frame: Baseline (prior to start of intervention) as a putative moderator.
IBS-BRQ is a 26-item measure of avoidance behavior. The scale has 26 items, scored from 1 (never) to 7 (always), indicating how persistently the particular avoidance or toilet behavior is carried out. IBS-BRQ is measured as a putative moderator.
Baseline (prior to start of intervention) as a putative moderator.
Total FODMAP intake measured using 3-day food diary
Time Frame: Baseline (prior to start of intervention) as a putative moderator.
Participants will record their food intake for 3 days (including one weekend day) using paper or an app. Total FODMAP intake will be calculated g/day. Total FODMAP intake is being measured as a putative mediator. Measured as a putative moderator.
Baseline (prior to start of intervention) as a putative moderator.
Credibility expectancy questionnaire (CEQ) questionnaire
Time Frame: End of week 2 of 12-week intervention
The Credibility & Expectancy Questionnaire is a 6-question measure of treatment expectancy and credibility. Credibility is derived from the first three 'think' (cognitively based) questions and expectancy is derived from the fourth 'think' question and the two 'feel' (affectively based) questions. Measured as a control variable.
End of week 2 of 12-week intervention
Working alliance inventory for guided internet intervention (WAI-I) questionnaire
Time Frame: End of week 2 of 12-week intervention
The Working Alliance Inventory for guided Internet interventions (WAI-I) is a 12 item tool to evaluate the working alliance in the context of guided Internet interventions. It consists of two subscale dimensions; Dimension 1: task and goal agreement with the program; and Dimension 2: bond with therapist. Items are rated on a 5-point Likert scale ranging from 1 (never) to 5 (always) and will be reported as a total score. Measured as a control variable.
End of week 2 of 12-week intervention

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
University of Melbourne

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Monash University

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Associate Professor Jessica Biesiekierski, University of Melbourne

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
May 22, 2025

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
October 1, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
April 1, 2028

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
March 31, 2025

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 15, 2025

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
April 23, 2025

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 6, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 29, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • CT31293
  • 2024 (Other Grant/Funding Number: Rome Foundation)
  • APP2025943 (Other Grant/Funding Number: NHMRC)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Potential data shared includes:

  • Individual participant data that underlie the results reported in the article after de-identification (text, tables, figures and appendices)
  • Trial protocol
  • Statistical Analysis Plan
  • Participant Information Consent Form

IPD Sharing Time Frame

The IPD and supporting information will be available beginning 3 months following analysis and article publication for 15 years.

IPD Sharing Access Criteria

The IPD and supporting information will be made available for use by future researchers from a recognized research institution whose proposed use of the data has been ethically reviewed and approved by an independent committee and who accept University of Melbourne conditions for access.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ICF
  • ANALYTIC_CODE
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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