7 Reasons Why the Low FODMAP Diet Might Not Be Working

7 Reasons Why the Low FODMAP Diet Might Not Be Working

7 Reasons Why the Low FODMAP Diet Might Not Be Working

If you are still suffering from abdominal pain and other IBS symptoms despite being low FODMAP, then it’s time to double check your diet and look at your stress levels. The low FODMAP diet is a learning diet and it can take a few weeks to change your food habits to make sure you aren’t eating high FODMAP foods. Additionally, even though many people experience symptom relief in the first couple of weeks, it can take longer for your body to adjust. Before you give up and decide the diet doesn’t work for you, there are a few things you need to check:

1. Ignoring recommended portion sizes for low FODMAP foods

I know it is easy to devour a large portion of a low FODMAP food when you discover something safe that you enjoy eating! However, you need to keep in mind that some low FODMAP foods become high FODMAP when you exceed a certain portion size (Muir, 2015; Scarlata, 2015).
A common example of this is rice cakes. Rice cakes make a delicious low FODMAP snack, especially when you top them with peanut butter or safe cheese. The recommended serving size is two rice cakes; if you increase your serving size to four they become high FODMAP as you will consume higher levels of fructans (oligosaccharides) (Monash University App, 2014).
This means it is important that you stick to the recommended serving sizes for low FODMAP foods. The Monash Low FODMAP app contains the most up-to-date lists of low and high FODMAP foods, as well as information on recommended serving sizes. If you want to increase your low FODMAP serving size, check the food for a warning note first. Please read my article on portion control and the low FODMAP diet for more information.

2. Consuming sneaky FODMAPs in processed foods, supplements & medications

Manufacturers often add high FODMAP ingredients to processed foods to enhance their texture and taste. Some common examples are: inulin, chicory root, agave syrup, HFCS, sorbitol (E420), mannitol (E421), maltitol (E956), xylitol (E967), and erythritol (E968).
The FODMAP content of most pharmaceutical tablets should not be high enough to cause any issues. However if you are having cough syrup, throat lozenges, or liquid suspensions that contain sugar alcohols then these could be making your symptoms worse. Also check your supplements and probiotics, as these can contain inulin, which is high FODMAP even in small amounts. Chewable supplements can also contain lactose, fructose, or sugar alcohols so read the ingredients carefully.

3. Having too much low FODMAP fruit in one meal

There are plenty of safe fruit options to choose from on the low FODMAP diet and it is easy to have too much fruit in one sitting. Low FODMAP dietitians recommend that you only have one serve of fruit at a time (Shepherd, 2011; Scarlata, 2015). You also need to stick to the recommended serving size for the fruit (unless you know you can tolerate more) (Shepherd, 2011; Scarlata, 2015). This means if you want to have two serves of fruit per day you can, but you need to leave at least two to three hours in between (Shepherd, 2011; Scarlata, 2015). To begin with I would recommend having one serve in the morning and another serve in the evening. Over time you can test your tolerance levels and see if you can reduce the time between your servings, or have more than two serves of low FODMAP fruit in a day.

4. Not consuming enough fibre to keep you regular

Fibre keeps us regular and plays an important part in our diet. The low FODMAP diet removes some high fibre foods, which means it is important that you make sure you are getting enough fibre. Insoluble fibre can be problematic for some people with IBS (Bijkerk et al., 2009; Ford et al., 2014; Francis & Whorwell, 1994), so you might need to focus on increasing your soluble fibre (you can find out more about the low FODMAP diet and fibre here). If your constipation has increased, then you should talk to your dietitian about your fibre intake, what fibre is appropriate, and if you need a fibre supplement. Also remember that you need to drink plenty of water (at least 4 to 6 cups per day) to help fibre work properly in your gut (Monash University App, 2014).

5. Ignoring other IBS trigger foods

Some low FODMAP foods may contain other common IBS trigger foods that need to be considered, to gain good symptom control. Other common IBS triggers foods include fatty or fried food, caffeine, alcohol, carbonated drinks, insoluble fibre, resistant starches, and spicy foods (BPACnz, 2014;NICE, 2015). You can find more information on these trigger foods here. If you think some of these trigger foods are causing your problems, you can remove them from your diet, along with the high FODMAP foods. Make sure you then test the foods you remove to make sure they are additional triggers.

6. Undiagnosed additional food intolerances

Even though a food may be low FODMAP, you might not be able to tolerate it. For example, I cannot tolerate lactose free milk or cheeses even though they are low FODMAP. This is because we have identified that I have an additional intolerance to dairy protein. To help you identify additional food intolerances you can keep a food diary. You and your dietitian can then review the diary and identify symptom patterns and potential trigger foods.

7. Stress as an IBS trigger

Stress can be a strong IBS trigger. This means if you are feeling stressed, it might not be just the food causing your symptoms. You may need a combination of the low FODMAP diet and stress management to manage your IBS symptoms.

Final Thoughts

If you are still having symptoms, despite being low FODMAP and dealing with the issues mentioned above, then further investigation might be needed. It is possible that you could have additional sensitivities to gluten, have food chemical intolerances (histamine, salicylate, amines, glutamates, sulphites), small intestine bacterial overgrowth (SIBO), or another condition that needs treatment (Gibson et al., 2014; Scarlata, 2014). Also note that the low FODMAP diet does not work for everyone. This means, if possible, you should work with a dietitian who has specialized in FODMAPs and gastroenterology, to find a treatment path that works for you.


1. Muir, J. Talking About the Traffic Light System. Monash University Low FODMAP Blog. 2015-02-05. Retrieved from:http://fodmapmonash.blogspot.co.nz/2015/02/talking-about-traffic-light-system.html. Retrieved on: 2015-07-12. (Archived by WebCite® at http://www.webcitation.org/6ZxV3MI5f)

2. Scarlata, K. Portion Size Matters on the Low FODMAP Diet. Well Balanced. 2015-04-28. Retrieved from:http://blog.katescarlata.com/2015/04/28/portion-size-matters-on-the-low-fodmap-diet/. Retrieved on: 2015-07-12. (Archived by WebCite® at http://www.webcitation.org/6ZxUrZqqR)

3. Monash University App.  Information Guide. The Monash University Low FODMAP Diet App. 2014: Edition 4. Date retrieved: 2015-03-05. Retrieved from :http://www.med.monash.edu/cecs/gastro/fodmap/iphone-app.html. Accessed: 2015-03-05. (Archived by WebCite® at http://www.webcitation.org/6Wog73c8B)

4. Shepherd, S. Food, FODMAPs and IBS: What to eat and what to avoid. Healthy Food Guide Magazine. 2011-11-09. Retrieved from:http://www.healthyfood.co.nz/articles/2011/november/food-fodmaps-and-ibs-what-to-eat-and-what-to-avoid#h2-7. Retrieved on: 2015-03-10. (Archived by WebCite® at http://www.webcitation.org/6WvtQsYse)

5. Bijkerk, C., Wit, N., Muris, J., Whorwell, P., Knottnerus, J., Hoes, A. Soluble or insoluble fibre in irritable bowel syndrome in primary care? Randomised placebocontrolled trial. British Medical Journal. 2009: Volume 339: Issue 7721. 613-615. DOI: 10.1136/bmj.b315 Retrieved from http://www.bmj.com/content/339/bmj.b3154.abstract Retrieved on 2015-03-24.

6. Francis, C. & Whorwell P. Bran and irritable bowel syndrom: Time for a reappraisal. The Lancet. 1994: Volume 334. 39-40. Retrieved from http://www.ibs-care.org/pdfs/ref_047.pdf

7. Ford, A., Moayyedi, P., Lacey, B., Lembo, A., Saito Y., Schiller, L., Soffer, E., Spiegel, B., & Quigley, E. American College of Gastroenterology Monograph on the Management of Irritable Bowel Syndrome and Chronic Idiopathic Constipation. Americal Journal of Gastroenterology. 2014: Volume 109: Supplement 1. S2-S26. Retrieved from http://gi.org/wp-content/uploads/2014/08/IBS_CIC_Monograph_AJG_Aug_2014.pdf Retrieved on: 24-03-24

8. BPACnz. Irritable bowel syndrome in adults: Not just a gut feeling. Best Practice Journal. 2014: Issue 58. 14-25. Retrieved from http://www.bpac.org.nz/BPJ/2014/February/ibs.aspx

9. NICE. Irritable bowel syndrome in adults: diagnosis and management of irritable bowel syndrome in primary care. National Institute for Health and Care Excellence. 2015. Retrieved from:http://www.nice.org.uk/guidance/cg61/chapter/1-recommendations. Retrieved on: 2015-06-07. (Archived by WebCite® at http://www.webcitation.org/6Z6RJ49TK)

10. Gibson, P. & Shepherd, S. Food Choice as a Key Management Strategy for Functional Gastrointestinal Symptoms. Americal Journal of Gastroenterology. 2012: Issue 107. 657–666. DOI: 10.1038/ajg.2012.49; p. Retrieved from http://www.med.monash.edu.au/general-practice/docs/food-choice-ajg-2012.pdf

11. Scarlata, K. Low FODMAP Diet is Not a Forever Diet. Well Balanced. 2014-09-02. Retrieved from:http://blog.katescarlata.com/2014/09/02/low-fodmap-diet-forever-diet/. Retrieved on: 2015-03-21. (Archived by WebCite® at http://www.webcitation.org/6XD0gY6EH)

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  • Wendy 18/08/2015 6:51am (2 years ago)

    I am so frustrated that I keep finding more and more things that there is a limit on. I have never heard there is a limit on ricecakes before. Is there anywhere, other than the app, where I can find out serving sizes? I can't get the app - I have no device on which to get it!

    Secondly, I am confused about the cumulative nature of FODMAPs. For example, if I have my two ricecakes, can I have peanut butter with them? I don't know what the recommended serving size of peanut butter is, but if the serving size of whole peanuts is only 10-15 nuts, surely that would only be about a teaspoon of peanut butter. And if I spread that on two ricecakes, wouldn't that make the overall amount of FODMAPs too much? Should I only be having one ricecake with a half-teaspoon of peanut butter? I already feel like I'm eating like a bird and often hungry, but I don't know what else I can eat apart from meat that doesn't have any FODMAPS.

    • Alana Scott 18/08/2015 8:48pm (2 years ago)

      Hi Wendy,
      I know it is frustrating. You can order a Monash Low FODMAP booklet that has the serving sizes for many of the foods they have tested - you can find the link here <a href="http://ecommerce.med.monash.edu.au/product.asp?pID=317&cID=11&c=194447" target="_blank" rel="nofollow">http://ecommerce.med.monash.edu.au/product.asp?pID=317&cID=11&c=194447</a> Peanut butter is low FODMAP and the save serve is 2 tablespoons. Monash has designed their traffic light system so that you can combine different low FODMAP foods together in one meal. This means in theory you should be fine to have two rice cakes and two tablespoons of peanut butter together but you will need to test your tolerance levels. To help you feel fuller you could try having your rice cakes and a low FODMAP smoothie, or low FODMAP muffin, or even a serve of low FODMAP fruit. Let me know if you need more help.

  • Jackie 24/08/2015 8:57am (2 years ago)

    Alana everything you have said makes absolute sense and I am so grateful and thankful for your advice and help !!! The rice cakes perfect example and very true stick to two ok more not ok. The fruit allowed have it all at once even though small banana and few strawberries not ok !!!! Banana then strawberries few hours later ok !!! I have learnt through your advice about portion sizes - even my cardiologist said 5 small meals a day Becausr I havePOTS. My other cardiologist said I had a leaky gut which will affect everything !!! So again thank you so much for all your time and effort into helping others and all while you are suffering too !!!!

    • Alana Scott 24/08/2015 10:06pm (2 years ago)

      Hi Jackie,
      I am so happy that you are finding my articles useful! I find it very rewarding to be able to help others on their FODMAP journeys. I think because I am walking my own FODMAP journey I am in a unique position to be able to help and understand others going through similar situations. Thank you so much for your kind words! Please let me know if there is anything I can do to help. Good luck on your FODMAP journey Jackie.

  • Dianne 29/08/2015 3:31pm (2 years ago)

    Alana, thank you so much for your dedication to educating us with your research and writing. This piece has been especially helpful for me. I've been watching portion sizes, but learned that I've been eating too many servings of safe fruit at one sitting! As you suggest, I am going to have one serving in the morning, and one in the evening. Then see if I can move them closer together. I never would have figured this out on my own!

    • Alana Scott 29/08/2015 11:03pm (2 years ago)

      Hi Dianne,
      I am so happy you are finding my articles useful! I would love to hear how you respond to changing your fruit consumption. I wish you all the best on your FODMAP journey. Let me know if there is anything else I can do to help. :-)

  • Denise 26/06/2016 2:54pm (15 months ago)

    My stomach has improved since being on the Fodmap diet and only get the occasional minor slip up..but,Ive now found that I get the stomach burn when I'm hungry (so just before I'm due for a meal.Is this normal or do I maybe have 2problems please.tia

    • Alana Scott 26/06/2016 8:27pm (15 months ago)

      Hi Denise,

      I'm glad to hear the low FODMAP diet is helping! I would encourage you to talk to your doctor and dietitian (if you have one) about the burning sensation. That symptom could indicate that there is something else going on so it is best that you get it checked by a medical professional. Thank you for commenting.


  • Wendy Ward 08/08/2017 12:01am (43 days ago)

    Hi I am trying the FODMAP diet , but know I cannot have anything with free glutamates. Some FODMAP safe food is full of these .

    • Alana Scott 09/08/2017 7:54pm (41 days ago)

      Hi Wendy,

      Yes a lot of low FODMAP foods are full of glutamates. Are you working with a dietitian? If you have other food intolerances then a dietitian would first make sure the low FODMAP diet is right for you, and then help you tailor the low FODMAP diet to suit your needs.

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