In the treatment of irritable bowel syndrome (IBS), the low FODMAP diet, when used appropriately, can provide essential benefits in reducing digestive symptoms — but do such dietary recommendations overlook, exacerbate — or even potentially cause disordered eating behaviors?

Such were the issues grappled with in a debate at the American College of Gastroenterology (ACG) 2025 Annual Scientific Meeting, resulting in general agreement that the diet has clearly demonstrated merits — but the possibility of eating disorders should be high on clinicians’ radars before recommending low FODMAP — or any other restrictive diet for patients with symptoms of IBS.

FODMAPs — or the short-chain carbohydrates of fermentable oligosaccharides, disaccharides, monosaccharides, and polyols that are not well-absorbed by the small intestine — can be key culprits associated with the traditional symptoms of IBS, including cramping, diarrhea, constipation, bloating, and gas and flatulence.

Under the three-stage low FODMAP diet, the first phase involves elimination of key FODMAPs, such as dairy- and wheat-based products, beans and lentils, and some fruits and vegetables, followed by phase 2, involving a gradual reintroduction of the foods to determine which may cause symptoms, and then, once those culprits are isolated, they are avoided or limited in the diet’s third phase of longer-term maintenance.

“The low FODMAP is fast and patient-empowering,” said Anthony Lembo, MD, of the Digestive Disease Institute at the Cleveland Clinic, in Cleveland, in making the case in favor of the diet.

The diet importantly represents a medication-sparing, low-risk approach, requiring only brief dietician support, he added.

“What’s notable is this is not a permanent diet — it’s personalized and gives patients control over their treatment, with just a brief limitation, with structured reintroduction of foods based on individual thresholds,” Lembo said.

Notably, studies show that as many as 50%-70% of patients achieve clinically meaningful relief in global symptoms of pain and bloating within 2-4 weeks, Lembo noted, adding that a comparison of other interventions — including the British Dietetic Association/National Institute for Health and Care Excellence dietary advice, sham dietary advice, and the high FODMAP diet — showed low FODMAP to be the most effective diet for IBS.

“If a pill had a 50%-70% response with this safety profile, we’d call it a breakthrough,” he noted.

“With guardrails, it expands diets — not restricts them — and it helps the majority of patients within 2-4 weeks, improving their quality of life.”

Importantly, studies show the diet also provides notable improvements in health-related quality of life and reduced healthcare costs, Lembo added.

Eating Disorders?

The caveat that looms large in the treatment of IBS is the risk that a fair proportion of patients may indeed have eating disorders that may not only be causing the IBS symptoms but could be inadvertently exacerbated by restrictive diets, said Kyle D. Staller, MD, MPH, in arguing against the FODMAP diet.

“Traditionally, we’ve placed eating disorders in the realm of dietitians and psychologists, but we now know that there is a bidirectional relationship between eating disorders and GI [gastrointestinal] symptoms, and many people with acute eating disorders will indeed meet criteria for functional GI disorders or disorders of gut-brain interaction (DGBI) — especially IBS,” cautioned Staller, the director of the Gastrointestinal Motility Laboratory at Massachusetts General Hospital and associate professor of medicine at Harvard Medical School in Boston.

Staller cited one important study showing that among patients presenting for GI consults with prior eating disorders, nearly half (44%) had eating disorders that were not in remission at the time of their GI consult.

The findings raise the important question of “How can we be sure that the patient that we’re seeing with a history of disordered eating is actually in remission?” Staller underscored.

Other recent findings from Staller’s own research team showed that of 279 patients with chronic constipation, 19% were found to have a clinically significant eating disorder pathology, with the eating disorders driven by GI-specific anxiety.

In addition to eating disorders commonly associated with body dysmorphia, patients with IBS symptoms could instead have avoidant/restrictive food intake disorder (ARFID), which may not be as readily recognized. Unlike some other eating disorders, ARFID is not motivated by shape or weight concerns but more by a fear and anxiety of food or the consequences of eating, such as choking.

According to further research from Staller and his team, nearly a quarter of patients (23.6%) referred to a neurogastroenterology center had probable ARFID. 

Staller noted that the importance of screening patients presenting with IBS symptoms for eating disorders is in fact described as “critical” in the guidelines from the American Gastroenterological Association, which state that “routine screening for disordered eating or eating disorders by careful dietary history is critical because they are common and often overlooked in gastrointestinal conditions.”

In his response, Lembo fully agreed that screening patients is essential, underscoring that “we should avoid giving not just the low FODMAP diet, but probably any diet to a patient that has, or is at risk of, ARFID.”

However, an association between the low FODMAP diet and ARFID does not necessarily equate to causation, particularly with the short duration of the diet, he argued.

“It would be unlikely that you would get ARFID from just a couple of weeks of reducing foods with this diet,” Lembo said.

While the FODMAP diet can indeed reinforce restrictive patterns, such cases are more likely if the diet is poorly implemented, which is common, he added.

If anything, “a short elimination, deliberate reintroduction with the low FODMAP clarifies triggers for patients and actually should expand the range of foods that patients eat, so it should be helpful for them.”

SCOFF Checklist for Screening

In response to the key question of how to screen GI patients for eating disorders, Staller suggested that one relatively quick and easy tool that can be highly useful is the five-question eating disorder screening tool, SCOFF, an acronym made from the key questions:

• Do you make yourself Sick because you feel uncomfortably full?
• Do you worry that you have lost Control over how much you eat?
• Have you recently lost more than One stone (14 lb) in a 3-month period?
• Do you believe yourself to be Fat when others say you are too thin?
• Would you say that Food dominates your life?

“The checklist gives these very quick questions, and you can use your gut instinct to determine which patients may really have an eating disorder like ARFID that is not necessarily based just on weight or body shape concerns,” Staller said.

In addition to the questionnaire, clinicians should follow their instinct. “A lot of times, it just doesn’t feel right,” Staller said. “You know those patients when you see them in clinic — every single thing discussed revolves around food, every single conversation about their symptoms revolves around food.”

“They’ve often already started to do some self-restriction — those are the patients I think we can really do a better job with by starting with ‘okay, maybe dietary treatment would not be the first choice.’”

FODMAP Gentle?

When an eating disorder is less clear, or the low FODMAP diet seems to be otherwise not ideal, both speakers supported the utilization of the “gentle” version of the low FODMAP diet.

Unlike the “top-down” approach of the standard FODMAP diet, a FODMAP-gentle diet uses a bottom-up approach, only restricting a select few foods that have a high concentration of FODMAPs, with further restriction only necessary if adequate symptom control is not initially achieved.

In most cases, but perhaps especially those, the utilization of a dietician can be essential in guiding patients and improving adherence, Staller said.

“The problem is that the majority of patients who implement a low FODMAP diet are not doing it under the guidance of a dietitian, and they’re not doing the reintroduction phase,” he said.

“Therefore, I think dietitians are really the saviors here,” Staller said. 

“When I started in my career, I thought dieticians were going to make everyone not eat anything, but what I’ve learned is that they are exceptionally good at screening for disordered eating,” he added.

William D. Chey, MD, chief of the Division of Gastroenterology & Hepatology at the University of Michigan in Ann Arbor, Michigan, agreed, noting that his experience with dieticians from around the world who attend a course for GI dieticians at the University of Michigan is that “the majority of dietitians are already doing [the FODMAP ‘gentle’] approach.”

“They’re using it in the trenches — they’re already using truncated versions of the low FODMAP diet based on data that’s been published on it,” he said. 

“This is why it’s such an advantage to work with a GI dietitian,” he added. “They’re really keeping up on this literature and have time to tailor what’s restricted based upon the patient’s previous history or experience.”

Staller acknowledged that “at the end of the day, I use the low FODMAP diet, and [Lembo] is right — it does have a mechanistic basis, it has more evidence than many other things, and the evidence is now showing that we can do it with less restriction.”

Importantly, as the diet has evolved, “it has been expanded to say that there are certain FODMAPs that are bigger triggers than others, and I think that may be the future.”

“If we can fundamentally only restrict one particular molecule or class, then that might be better,” Staller said.

“I still — and this is my bias — worry that restriction can be a pathway for certain patients, so we really have to check in frequently.”

Lembo reported consulting and/or other relationships with Ironwood, Vibrant, Atmo, BioAmerica, Ardelyx, Takeda Pharmaceuticals, Gemelli Biotech, Evoke, Johnson & Johnson, Bristol Myers Squibb, and Acadia Pharmaceuticals. Staller reported consulting and/or other relationships with Anji, Ardelyx, Gemelli Biotech, Laborie, Mahana, ReStalsis, Salix Pharmaceuticals, Sanofi, and Takeda Pharmaceuticals. Chey reported consulting and/or other relationships with Ardelyx, Atmo, Biomerica, Commonwealth Diagnostics International, Corprata, Dieta, Evinature, Food Marble, Gemelli Biotech, Kiwi Biosciences, Modify Health, Nestle, Phathom Pharmaceuticals, Redhill, Salix Pharmaceuticals/Valeant Pharmaceuticals, Takeda Pharmaceuticals, and Vibrant.