A Five-Day-a-Month Diet Shows Promise for Crohn’s Disease Relief

January 13, 2026 - By Rebecca Handler 

For people living with Crohn’s disease, a common question often goes unanswered: Can diet actually make a difference? A new Stanford-led clinical trial offers encouraging evidence that a short, structured dietary program — used for only five days each month — may help reduce symptoms and inflammation in adults with mild to moderate Crohn’s disease.

The trial, led by Sidhartha Sinha, MD, assistant professor of medicine in the Division of Gastroenterology and Hepatology, tested what’s called a fasting-mimicking diet (FMD). It’s a plant-based, low-calorie meal plan designed to shift the body temporarily into a “fasting-like” metabolic state while still allowing people to eat. Patients followed the diet for five consecutive days each month and returned to their usual diet the rest of the time.

This was the largest randomized controlled trial of an oral diet intervention in adults ever conducted in Crohn’s disease and provides a rare level of evidence in a field where, despite the need and desire from patients and providers, high-quality diet studies are uncommon.

Understanding Crohn’s Disease 

Crohn’s disease is a chronic inflammatory condition in which the immune system mistakenly targets parts of the digestive tract. The inflammation it causes can lead to symptoms such as abdominal pain, diarrhea, fatigue, and unintended weight loss. The disease usually cycles between flares and quieter periods that shift over time. Medications are effective for many people, but there are limited treatment options for those with milder disease, and no FDA-approved therapies for long-term maintenance at that stage beyond steroids, which can cause a wide array of side effects. At the same time, many patients wonder whether dietary changes could help. Despite the interest, scientific evidence supporting specific diets in Crohn’s disease has been limited.

This is where the new trial offers something different: a structured, evidence-based look at a diet that is short in duration, easier to follow than restrictive daily diets, and – unlike most diet studiesn– is paired with biological data that helps explain why it may work.

A Practical, Short-Term Dietary Approach

The fasting-mimicking diet was chosen because it does not require constant caloric restriction or long term changes to diet. Instead, it uses short, monthly cycles intended to create a temporary metabolic shift. As Sinha explains, “Many dietary approaches require major ongoing changes that are difficult to sustain. What stood out about this diet is that it’s short, structured, and designed to be realistic for people to follow.”

Ninety-seven adults with mild to moderate Crohn’s disease participated in the trial. Those assigned to the fasting-mimicking diet followed the five-day program once a month for three months. For the remaining days, they were instructed not to change their usual eating patterns. The comparison group continued their baseline diet throughout the study.

By the end of the third cycle, nearly seven in ten people in the fasting-mimicking group showed a clinical response, marked by meaningful improvements in their Crohn’s symptoms. Fewer than half did in the comparison group. Clinical remission (experiencing minimal or no symptoms) was also more common among those using the five-day cycles. It’s worth mentioning that the trial was designed to mimic real world conditions and patients continued standard care treatment for their Crohn’s. Notably, there were no major differences in rates of medications used at baseline or in escalation of therapy (such as starting new advanced therapies/ steroids or increasing the dose of advanced therapy) during the study period between the FMD and control arms.

Sinha said his team did not expect improvements to appear so quickly. “We were struck not only by the large proportion of patients who responded, but also by how rapidly they did — showing clinically meaningful improvement after even just a single FMD cycle,” he noted. “Patients spent most of the month eating normally, yet the short, structured periods of the diet still had a notable clinical and biochemical effect.”

Signs of Reduced Inflammation

Because Crohn’s disease is driven by inflammation in the digestive tract, the researchers also examined biological markers to see whether the improvements in symptoms were reflected in the body.

One key marker was fecal calprotectin, a protein released into stool when the intestines are inflamed. High levels typically signal active disease, while decreases suggest improvement. Over the course of the study, average fecal calprotectin levels decreased in the fasting-mimicking group but rose in the comparison group.

Blood testing added additional insight. Participants following the fasting-mimicking diet showed reductions in several inflammatory molecules and changes in immune-related gene activity. According to Sinha, “During those five days, the body shifts into a state that naturally lowers inflammatory signaling. We saw consistent reductions in molecules that are known to drive Crohn’s pathology and symptoms.”

These findings provide a biological explanation for the clinical improvements and help situate the diet within the larger understanding of how metabolism and the immune system interact. The team also collected an extensive set of additional biospecimens across the trial, and analyses of these samples are ongoing and expected to yield additional mechanistic insights.

How This Fits Into Crohn’s Care

Even with these encouraging results, Sinha emphasizes that the fasting-mimicking diet is not meant to replace standard medical therapy. Although the data are still emerging, the evidence points to the best outcomes when medication and thoughtful dietary strategies are used together,” he said. “We view this approach as a complement to standard therapies, not a replacement.”

Because the diet is short and structured, it may be more practical for patients who struggle with restrictive diets that require daily commitment. It may also appeal to those with mild disease who have limited evidence-based options beyond intermittent use of steroids.

Sinha cautions that patients should discuss any diet changes with their medical team, as nutritional needs and disease management vary from person to person.

What Comes Next

The research team hopes to build on these findings by testing the diet in larger and more diverse populations, studying how long the benefits last, and identifying which individuals are most likely to respond. Scientifically, they are now focused on refining the biology behind how the fasting-mimicking diet works. By pinpointing the inflammatory pathways, lipid mediators, or microbial and metabolomic changes that shift during the intervention, the team aims to identify the mechanistic signatures that predict response. “If we can understand why the diet works for certain people, we can begin matching specific dietary strategies to an individual’s biology,” Sinha noted. They also plan to explore whether similar short-term diet cycles could benefit people with related autoimmune conditions.

“Our goal is to move toward a precision-nutrition model,” Sinha said. “One where we match the right dietary strategy to the right person, just as we do with medications.”

But Sinha notes that progress in this area has long been held back by the fact that diet and nutrition research is dramatically underfunded compared with drug development. “Diet therapy in Inflammatory Bowel Disease (IBD) has long been a paradox — patients are deeply interested, clinicians historically hesitant,” he said. “A major reason for this hesitation is that we simply lack robust dietary studies in IBD and across medicine. Nutrition research receives far less funding than pharmacologic development, which limits the number of large, well-designed trials we can run.”

He believes that this study can help shift that mindset. “My hope is that these results encourage clinicians and researchers to view diet as a legitimate, complementary therapeutic tool — one that warrants the same scientific attention and investment as other strategies for chronic inflammatory diseases.”

For people living with Crohn’s disease, this study offers a new and evidence-based option to consider that may help ease symptoms and reduce inflammation in a way that is practical to maintain. As Sinha put it, “More than anything, we hope this gives patients another safe, realistic tool to support their health.”