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

NCT07829666 | Completed

• 1 other identifier: 2023-16/560
• Study Type: interventional
• Target: 90
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Irritable Bowel Syndrome

Keywords

Low-FODMAP Diet; NICE Dietary Advice; Intermittent Fasting; 16:8 Intermittent Fasting; Irritable Bowel Syndrome

Outcome Measures

Primary Outcomes (1)

• Change in Irritable Bowel Syndrome Symptom Severity

  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.

  Baseline to 2 weeks

Secondary Outcomes (1)

• Change in Irritable Bowel Syndrome-Specific Quality of Life

  Baseline to 2 weeks

Study Arms (3)

Low-FODMAP Diet (LF)

EXPERIMENTAL

Participants in this arm 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.

Behavioral: Low-FODMAP Diet

Adapted NICE Dietary Advice (NICE)

ACTIVE COMPARATOR

Participants in this arm 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 fruit intake to a maximum of three servings (240 g) per day, limiting tea and coffee to a maximum of three cups per day, and limiting alcohol and carbonated beverages. No specific restriction on fiber or FODMAP intake was applied.

Behavioral: Adapted NICE Dietary Advice

Adapted NICE Dietary Advice Plus Intermittent Fasting (NICE-IF)

ACTIVE COMPARATOR

Participants in this arm followed adapted NICE dietary advice combined with a 16:8 intermittent fasting regimen 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.

Behavioral: 16:8 Intermittent Fasting

Interventions

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.

Low-FODMAP Diet (LF)

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

Adapted NICE Dietary Advice (NICE)

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.

Adapted NICE Dietary Advice Plus Intermittent Fasting (NICE-IF)

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• 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)

You may not qualify if:

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

Sponsors & Collaborators

• Acibadem University: lead

Study Sites (1)

Acibadem Kozyatagi Hospital

Istanbul, Turkey (Türkiye)

Location

MeSH Terms

Conditions

Irritable Bowel Syndrome; Intermittent Fasting

Interventions

FODMAP Diet

Condition Hierarchy (Ancestors)

Colonic Diseases, Functional; Colonic Diseases; Intestinal Diseases; Gastrointestinal Diseases; Digestive System Diseases; Fasting; Feeding Behavior; Behavior

Intervention Hierarchy (Ancestors)

Elimination Diets; Diet; Nutritional Physiological Phenomena; Diet, Food, and Nutrition; Physiological Phenomena

Study Officials

• Nur E Baydı Ozman, PhD

  Acibadem Atasehir Hospital

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: September 15, 2026
• First Posted: September 21, 2026
• Study Start: February 1, 2024
• Primary Completion: November 1, 2024
• Study Completion: November 1, 2024
• Last Updated: September 21, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

TU (1)