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What is the Low FODMAP Diet?

Steak on plate with roasted potatoes and rosemary garnish

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The Low FODMAP Diet was developed by Monash University in 2005. The diet consists of three phases: the first clears up your symptoms, the second, tests your tolerance to individual FODMAP groups, and the third and final phase reintroduces foods you can tolerate and eat long-term. The end goal is a designer low FODMAP diet tailored to your personal digestive needs.

Before you begin reading, make sure to check out my previous article What is a FODMAP? to make sure you understand what you are testing.

Phase One: Elimination Phase

During this phase, all high FODMAP foods are removed from the diet for of 2-6 weeks. Removing high FODMAP triggers should reduce or relieve IBS symptoms within one month. The success of the elimination phase depends on your complete adherence to the elimination diet. You may also need to consider external triggers such as stress within your personal life, the quality of your sleep, and your current level of health.

Use this time to determine what your “normal” is. If you have been suffering from severe symptoms for a long time, you may have forgotten what your normal bowel movements look like. Keep a diary of what goes in and what comes out of your body during this phase. Knowing what a normal bowel movement looks and feels like will help you describe symptoms when they arise. This will be handy information when you enter phase two.

Phase Two: Re-Challenge Phase

In the second phase, each FODMAP group is tested one at a time. This involves eating a specific test food in increasing amounts over three days. With the exception of the test food you will stay on the elimination diet. You will then return to the elimination diet proper for a “washout” period. This will relieve any symptoms triggered by that particular group so you can start your next test symptom-free. You can find specific instructions for completing the re-challenge phase here.

This phase is completed in 4-6 weeks depending on the number of groups to be tested. For example, if you know you are lactose intolerant before you begin the elimination phase, you will not need to test this group again.

It is especially important to keep a diary of what you eat and any symptoms you experience during this time. This will help both you and your dietitian determine what foods you can eat long-term. Keeping a record of symptoms you encounter may also provide information about how your body reacts to each FODMAP group.

Phase Three: Re-Introduction

During the reintroduction phase, individual foods from each FODMAP group are reintroduced into your long-term diet. This often begins with groups that were well tolerated and moves gradually toward groups that were less tolerable.

Tests are performed using the portion you would normally eat. This process is much faster than phase two, as foods are tested by alternating test days and rest days. If the food you are testing causes symptoms, you can always try testing a smaller portion.

Any group which caused severe symptoms in phase one should be discussed with your dietitian before phase three testing begins. They will determine how you approach the reintroduction of this group and if there are specific foods you should avoid long-term.

Long-Term Maintenance

Over time your dietary needs may change. For example, our bodies produce less lactase – the enzyme that breaks down lactose – as we age. This means your sensitivity to lactose may change as you grow older. You may also find that you can add items over time. Because of this, it may be in your best interest to re-test groups periodically to check for changes.

You may also experience periods in your life when the modified diet you have settled on isn’t working. This may happen for several reasons: 1) Your portions may have increased over time.  2) You may be suffering from excessive stress or lack of sleep; both of which can decrease your tolerance for FODMAPs you normally enjoy.  3) Your tolerance to a specific FODMAP group may have changed over time and need to be reassessed.

If you are experiencing symptoms after a period of relief, first, check the labels on items you eat regularly. Companies do not alert you when they change the ingredients in their products. Therefore, you may have added some FODMAPs to your diet without your knowledge.

You might also consider assessing external factors like your current level of stress, your sleep hygiene, your physical health, etc. Try getting some extra sleep, delegating some tasks at home or at work, and finding some time to be nice to your body.

If you can’t pinpoint what the issue is, go back to the elimination diet until you feel better. If that doesn’t relieve your symptoms, you might consider a trip to your doctor as something else might be mimicking IBS symptoms and require your attention.

Thanks for reading! I hope you learned something helpful about the Low FODMAP Diet.  Please leave any comments or questions below, and, if you haven’t already, take a look at my previous article What is a FODMAP? to learn more about the FODMAP family.

Did you like this article? You might also like one of these:

How to Complete the Re-Challenge Phase

How to Prepare for the Low FODMAP Diet

Living on the Low FODMAP Diet

© Copyright 2017 Amy Agur – The FODMAP Formula



Leave a Comment

  • Akhtar

    I have ibs with constipation

    • Amy Agur

      Hi, Akhtar!

      The Low FODMAP Diet helps with all 4 subcategories of IBS. While each group’s needs are a little different, the Low FODMAP Diet does help 75-80% of IBS patients control their symptoms long-term.


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