Researchers studied 30 people with irritable bowel syndrome (IBS) who followed a special diet low in certain hard-to-digest carbohydrates for 12 weeks. They found that this diet not only reduced IBS symptoms and helped people lose weight, but it also increased levels of a hormone called GLP-1 in the blood. GLP-1 is a natural chemical that helps control digestion and may play a role in managing IBS. While the exact reason why this diet boosts GLP-1 isn’t completely clear yet, these results suggest the diet works in multiple helpful ways for people with IBS.

The Quick Take

  • What they studied: Whether eating a diet that avoids certain types of carbohydrates (called a low FODMAP diet) changes the levels of a gut hormone called GLP-1 in people with IBS
  • Who participated: 30 adults with irritable bowel syndrome, specifically those with diarrhea-type or mixed-type IBS symptoms
  • Key finding: After 12 weeks on the low FODMAP diet, GLP-1 hormone levels increased significantly in the blood (p = 0.027), and people also experienced fewer IBS symptoms and lost weight
  • What it means for you: If you have IBS, this diet may help you feel better by reducing symptoms and potentially triggering your body to produce more of a helpful hormone. However, this is early research, and you should talk to a doctor before making major diet changes

The Research Details

This was a straightforward study where researchers recruited 30 people diagnosed with IBS and asked them to follow a low FODMAP diet for 12 weeks. FODMAP stands for certain types of carbohydrates found in foods that can be hard for some people to digest—things like wheat, certain fruits, beans, and dairy products. The researchers measured three things before and after the diet: the amount of GLP-1 hormone in people’s blood, how severe their IBS symptoms were using a standard scoring system, and their body weight.

The low FODMAP diet removes foods that contain these hard-to-digest carbohydrates and replaces them with easier-to-digest options. This approach has been used for years to help IBS patients feel better. What’s new here is that the researchers specifically looked at whether this diet changes GLP-1 levels, which hadn’t been studied much before.

This type of study is useful because it shows what actually happens when real people follow this diet in their daily lives, rather than just testing it in a lab.

Understanding how diet affects the body’s natural chemicals is important because it helps explain why certain diets work for certain conditions. GLP-1 is a hormone that your gut naturally produces, and it helps control digestion, blood sugar, and even appetite. If we can show that a simple diet change increases GLP-1, it gives us a clearer picture of how the low FODMAP diet helps IBS patients feel better. This knowledge could help doctors recommend this diet with more confidence and might inspire new treatments based on boosting GLP-1.

This study has some strengths: it measured multiple outcomes (symptoms, weight, and hormone levels), used a standard scoring system for IBS severity, and followed people for a reasonable length of time (12 weeks). However, there are some limitations to keep in mind: the study didn’t include a control group of people eating a regular diet for comparison, the sample size is relatively small (30 people), and we don’t know if the benefits lasted beyond the 12-week period. The study was published in a reputable nutrition journal, which is a good sign, but the results should be confirmed by larger studies before drawing firm conclusions.

What the Results Show

The main finding was that GLP-1 hormone levels increased after 12 weeks on the low FODMAP diet. This increase was statistically significant, meaning it’s unlikely to have happened by chance. In addition to the hormone increase, people’s IBS symptoms improved noticeably—their IBS Severity Scoring System scores went down, which means they experienced fewer and less intense symptoms like bloating, pain, and irregular bowel movements.

People also lost weight during the 12 weeks, which is an additional benefit. The researchers also confirmed that people were actually eating less FODMAP (the hard-to-digest carbohydrates) by the end of the study, which shows they were following the diet correctly.

These three outcomes—higher GLP-1, fewer IBS symptoms, and weight loss—all happened together, suggesting the diet works through multiple beneficial pathways in the body. However, the study doesn’t prove that the increased GLP-1 directly caused the symptom improvement; they may be separate benefits of the diet.

The study also tracked FODMAP intake to confirm that participants were actually reducing their consumption of these carbohydrates. The fact that FODMAP intake decreased significantly shows that people were able to follow the diet as instructed. The weight loss that occurred was modest but meaningful, and it happened without people being told to restrict calories, suggesting the diet naturally leads to eating less.

The low FODMAP diet has been studied extensively and is already known to help many IBS patients feel better. What’s new here is the connection to GLP-1. Previous research has shown that GLP-1 plays a role in gut health and digestion, and some studies suggest it may help with IBS symptoms. This study appears to be one of the first to directly measure whether the low FODMAP diet increases GLP-1 levels. The findings fit with what we know about how the diet works, but they add a new piece to the puzzle by identifying a possible biological mechanism.

Several important limitations should be considered: First, the study had no control group—researchers didn’t compare the low FODMAP diet to a regular diet or a placebo, so we can’t be completely sure the diet itself caused the changes rather than other factors like placebo effect or natural improvement over time. Second, the sample size of 30 people is relatively small, which means the results might not apply to all IBS patients. Third, the study only lasted 12 weeks, so we don’t know if the benefits continue longer or if people can stick with the diet long-term. Fourth, the study doesn’t explain why the diet increases GLP-1—the mechanism remains unknown. Finally, the study included only people with diarrhea-type or mixed-type IBS, so results may not apply to people with constipation-type IBS.

The Bottom Line

If you have IBS, particularly diarrhea-type or mixed-type IBS, the low FODMAP diet appears to be worth trying under professional guidance. The evidence suggests it may reduce your symptoms, help you lose weight, and increase a helpful gut hormone. However, this is based on a relatively small study, so consider it promising but not definitive. We recommend: (1) Talk to your doctor or a registered dietitian before starting the diet, (2) Give it at least 12 weeks to see if it helps, (3) Keep track of your symptoms to see if you improve, and (4) Be patient—the diet requires learning which foods to avoid, but many people find it worthwhile. Confidence level: Moderate—the results are encouraging but need confirmation from larger studies.

This research is most relevant for people with IBS, especially those with diarrhea or mixed symptoms. It may also interest people with other digestive issues who haven’t found relief with other treatments. Healthcare providers treating IBS patients should be aware of these findings. However, if you have constipation-type IBS, this study doesn’t specifically address your situation, so talk to your doctor about whether the diet might help you. People without IBS probably don’t need to follow this diet, as it’s specifically designed for those with digestive sensitivities.

Based on this study, you should expect to see improvements in IBS symptoms within 12 weeks of starting the diet. Some people may notice changes sooner (within 2-4 weeks), while others may take the full 12 weeks. Weight loss, if it occurs, typically happens gradually over the 12-week period. The increase in GLP-1 hormone appears to happen within this timeframe, though individual variation is likely. Keep in mind that the diet requires an adjustment period as you learn which foods to avoid, so the first week or two might feel challenging.

Want to Apply This Research?

  • Track daily IBS symptoms using a simple 1-10 severity scale, noting bloating, abdominal pain, and bowel movement frequency. Also log which foods you eat to identify patterns and ensure you’re following the low FODMAP guidelines correctly.
  • Use the app to create a low FODMAP food list with allowed and avoided items. Set daily reminders to drink water and eat meals at regular times. Log meals before eating to check if foods are FODMAP-friendly, and track symptom improvements weekly to stay motivated.
  • Establish a weekly review routine where you compare your symptom scores from week to week. Create a chart showing symptom trends over the 12-week period. Monitor weight weekly if desired. After 12 weeks, assess overall improvement and decide whether to continue the diet based on your results. Consider sharing your tracked data with your healthcare provider to discuss next steps.

This research summary is for educational purposes only and should not be considered medical advice. The study involved a small number of participants and has not yet been confirmed by larger research. Before starting a low FODMAP diet or making significant dietary changes, especially if you have IBS or other digestive conditions, please consult with your doctor or a registered dietitian. They can assess whether this diet is appropriate for your specific situation, help you implement it correctly, and monitor your progress. If you experience severe abdominal pain, persistent diarrhea, or other concerning symptoms, seek immediate medical attention. Individual results may vary, and what works for one person may not work for another.