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NCT Number: NCT07829666

Short-Term Effects of Low-FODMAP, NICE Dietary Advice, and Intermittent Fasting in Irritable Bowel Syndrome

The goal of this clinical trial is to compare the short-term effects of three dietary approaches in adults with irritable bowel syndrome (IBS): a low-FODMAP diet, adapted National Institute for Health and Care Excellence (NICE) dietary advice, and adapted NICE dietary advice combined with 16:8 intermittent fasting.

The main questions this study aims to answer are:

How do these three dietary approaches affect IBS symptom severity after two weeks? How do these three dietary approaches affect IBS-related quality of life after two weeks? The researchers hypothesize that the low-FODMAP diet will produce the greatest short-term reduction in IBS symptom severity. The study will also explore whether adding 16:8 intermittent fasting to adapted NICE dietary advice provides additional benefit.

Researchers will compare the three dietary groups to determine whether the changes in IBS symptoms and quality of life differ between the dietary approaches.

Participants will:

Follow one of the three dietary approaches for two weeks. Attend study visits at the beginning of the study, after one week, and after two weeks.

Keep records of their food and fluid intake. Complete questionnaires about IBS symptoms, quality of life, anxiety, and depression.

Record their stool form and frequency during the study.

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Key information

Conditions

Irritable Bowel Syndrome Behavior Colonic Diseases Colonic Diseases, Functional Digestive System Diseases Fasting Feeding Behavior Gastrointestinal Diseases Intermittent Fasting Intestinal Diseases

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Acibadem Kozyatagi Hospital

Istanbul, Turkey (Türkiye)

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Adults aged 18-65 years Diagnosis of irritable bowel syndrome (IBS) according to the Rome IV criteria IBS subtype classified as IBS with constipation (IBS-C), IBS with diarrhea (IBS-D), or IBS with mixed bowel habits (IBS-M)

Exclusion criteria

Celiac disease Inflammatory bowel disease History of cancer Diabetes Kidney disease Pregnancy Current adherence to an elimination diet

Treatment and study plan

Low-FODMAP Diet

Behavioral

Participants followed a researcher-designed low-FODMAP elimination diet for two weeks. The dietary intervention was delivered by a dietitian who had completed Monash University Low-FODMAP Diet Training. Foods containing fermentable oligosaccharides, lactose, excess fructose, and polyols were restricted. The reintroduction phase of the low-FODMAP diet was not implemented during the two-week study period.

Adapted NICE Dietary Advice

Behavioral

Participants followed adapted NICE dietary advice for two weeks. The recommendations included eating regular meals and avoiding prolonged fasting, drinking at least 2 liters of water per day, limiting

16:8 Intermittent Fasting

Behavioral

Participants followed a 16:8 intermittent fasting regimen in addition to adapted NICE dietary advice for two weeks. All meals were consumed within an 8-hour eating window, either from 11:00 to 19:00 or from 12:00 to 20:00, followed by a 16-hour fasting period. One or two snacks were permitted within the eating window. No specific restriction on fiber or FODMAP intake was applied.

Primary outcomes

  1. Change in Irritable Bowel Syndrome Symptom Severity

    Time frame: Baseline to 2 weeks

    IBS symptom severity was assessed using the Irritable Bowel Syndrome Severity Scoring System (IBS-SSS). The total score ranges from 0 to 500, with higher scores indicating greater symptom severity. A reduction of at least 50 points was considered a clinically meaningful improvement.

Secondary outcomes

  1. Change in Irritable Bowel Syndrome-Specific Quality of Life

    Time frame: Baseline to 2 weeks

    IBS-specific quality of life was assessed using the Irritable Bowel Syndrome Quality of Life questionnaire (IBS-QOL). The questionnaire consists of 34 items across eight subscales. Scores are transformed to a 0-100 scale, with higher scores indicating better IBS-specific quality of life.

Sponsors and collaborators

Lead sponsor

Acibadem University

Other

Registry information

Official study title

Short-Term Effects of a Low-FODMAP Diet, Adapted NICE Dietary Advice, and Adapted NICE Dietary Advice Combined With Intermittent Fasting on Symptoms and Quality of Life in Irritable Bowel Syndrome: A Three-Arm, Non-Randomized Controlled Dietary Intervention Study

Important dates

Study start
2024
Primary completion
2024
Study completion
2024
First posted
Sep 21, 2026
Registry last updated
Sep 21, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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