Low-FODMAP Diet and CBT for IBS: Efficacy Data and Individualizing Treatment

mid adult woman clutches stomach
Authors describe efficacy data on the low-FODMAP-diet and CBT for IBS and factors to consider when personalizing treatment.

Irritable bowel syndrome (IBS) is a gastrointestinal (GI) disorder characterized by chronic abdominal pain, alteration in bowel habits, diarrhea, and constipation that occur at least 1 day per week over a 3-month period.1 The estimated prevalence of IBS is 4.4% to 4.8% in the United States, United Kingdom, and Canada, and the condition is more prevalent in women and individuals younger than 50 years.1 The exact etiology of IBS is unknown but is thought to be related to intestinal inflammation, GI motility disturbances, altered microbiota, and visceral hypersensitivity, which are often seen in IBS patients.2 Many factors appear to exacerbate the condition such as increased stress, anxiety, depression, certain foods (gluten and carbohydrate intolerances), and changes in gut flora.2,3

Numerous treatment modalities have been reviewed and trialed including education programs, dietary modification, medication, behavioral therapy, and physical activity.4 Among these strategies, the low fermentable oligosaccharides, disaccharides, monosaccharides, polyols (FODMAP) diet and cognitive-behavioral therapy (CBT) are commonly used for symptom management in patients with IBS.

FODMAP Diet for Irritable Bowel Syndrome

FODMAPs are short-chain carbohydrates such as fructose, lactose, sugar alcohols, fructans, and galactans.5 These carbohydrates are in a wide range of foods such as wheat, rye, vegetables, legumes, and fruits. Short-chain carbohydrates are poorly absorbed in the small intestine and colon, increasing osmotic pressure in the large-intestine lumen, and increasing water content of the stool.5 The liquid stool provides a substrate for bacterial fermentation and gas production resulting in abdominal distension along with pain and/or discomfort.5 Research suggests that a low FODMAP diet may reduce these symptoms.

In a meta-analysis of 7 randomized controlled trials (N=397), the low FODMAP diet was associated with a significant reduction in global IBS symptoms compared with different comparators (risk ratio [RR], 0.69; 95% CI, 0.54-0.88).6 Three trials included in the meta-analysis compared the low FODMAP diet with an alternative diet and showed a nonsignificant trend favoring the low FODMAP diet (RR, 0.82; 95% CI, 0.66-1.02).6 In a more recent meta-analysis of 12 studies, the low-FODMAP diet was associated with a moderate-to-large reduction in IBS severity compared with control diets (standardized mean difference, -0.66; 95% CI, -0.88 to -0.44; I2 = 54%).7

The FODMAPS diet consists of 3 phases1,8,9:  

  1. Elimination: Patients eliminate all FODMAPs from their diet for 2 to 6 weeks
  2. Reintroduction: FODMAP subgroups are gradually reintroduced to identify specific symptom triggers. This phase may last 6 to 8 weeks.
  3. Maintenance or personalization: Patients only restrict those foods that trigger symptoms

Tolerance to certain FODMAPs may change over time, so patients may attempt to reintroduce certain trigger foods after they have achieved symptom control over a period of time.7 Communication with patients during all phases of the diet is important to assess compliance level, identify barriers, and integrate outside resources, education, or consults as needed for successful treatment.

The low FODMAP diet is most effective in managing IBS symptoms in patients who strictly adhere to the dietary changes.7 However, long-term diet adherence may be challenging for patients. In a study of 233 patients with IBS who initiated the FODMAP diet, 59% of patients did not adhere to the diet at 6-week follow-up. Future studies are needed to examine the long-term effects of the FODMAP diet in larger cohorts, including in patients with lower levels of diet adherence.

Cognitive-Behavioral Therapy for Irritable Bowel Syndrome

The brain-gut axis plays a key role in IBS and CBT has demonstrated efficacy in reducing IBS symptoms in clinical studies.11 In one randomized study involving patients with refractory IBS (N=558; n=323 achieved 24-month follow-up), both web-based CBT with minimal therapist support and therapist-delivered telephone CBT were significantly associated with improvements in IBS symptoms compared with treatment as usual (continuation of current medications) at 12-month follow-up; these improvements were sustained at 24-month follow-up.12 In-person treatment proved to be more beneficial than web-based and telephone-based treatment in this study with the mean IBS Symptom Severity Score 40.5 points lower in the telephone-CBT group (95% CI, 15.0-66.0; P =.002) and 12.9 points lower in the web-CBT group (95% CI, -12.9 to 38.8; P =.33) than in the treatment as usual group at 24 months.12 The CBT intervention consisted of the following12:

  • Behavior techniques to improve bowel habits
  • Healthy exercise patterns and diet
  • How to address unhelpful thoughts
  • Emotional management
  • Education surrounding the brain-gut axis
  • Relapse prevention guides

A meta-analysis of 42 randomized controlled trials involving 4072 patients with IBS showed efficacy of self-administered or minimal contact CBT (RR, 0.61; 95% CI, 0.45-0.83; P = .66) and in-person CBT (RR, 0.62; 95% CI, 0.48-0.80; P =.65) in reducing IBS symptoms.13 The pivotal studies of gut-directed psychotherapy have included patients treated with pharmacotherapies for CBT and there are no studies comparing CBT to pharmacotherapies.1 

A barrier to CBT use is the limited number of therapists with adequate training in GI-directed psychotherapies psychology.11

Clinical Implications

The American College of Gastroenterology (ACG) recommends a stepwise approach to caring for patients with IBS.1 The first steps start with testing to rule out celiac disease or inflammatory bowel disease and keeping a journal listing foods and GI symptoms. Next, the ACG recommends avoiding foods that are found to trigger symptoms; for some patients this means avoiding dairy products and high-fat foods. The ACG recommends adding soluble fiber to patients’ diets, a limited trial of a low FODMAP diet, use of peppermint oil, GI-directed psychotherapies (including CBT), and medications based on IBS subtype (see the guidelines for details on recommended medications).


Irritable bowel syndrome is a complicated syndrome that presents with a range of triggers and symptoms, making individualized treatment plans essential. The FODMAP diet and CBT are both effective treatments that can help reduce symptoms of IBS including abdominal pain, bloating, and diarrhea. Clinicians should discuss all available options for the management of IBS and identify patients’ willingness to comply with treatments such as a low-FODMAP diet or CBT, acknowledging that the FODMAP diet may be difficult for some patients to maintain in the short- or long-term. Cognitive-behavioral therapy may be limited by patient resistance to psychological treatment, specialist shortages, and delays in appointments times.

Laresse Harris, MSN, APRN, FNP-C, graduated from Indiana State University in 2020 and is board certified as a Family Nurse Practitioner She currently works full-time in primary care and enjoys caring for her patients, actively listening to address their concerns, and ensuring they receive top-quality evidence-based practices. She is also actively enrolled in the Doctor of Nursing Practice program at ISU, to continue her academic advancement.

Jaime Key, MSN, ARNP, FNP-C, graduated from Indiana State University with a Master’s of Science in Nursing degree. A board-certified Family Nurse Practitioner, she is currently practicing in a primary care clinic setting in Washington State, treating a wide variety of patient concerns.


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This article originally appeared on Clinical Advisor