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FODMAP Diet Phases 1-3: The Journey Towards Managing Your IBS

What is the FODMAP Diet?

The FODMAP diet is a therapeutic diet and is often recommended to those who have Irritable Bowel Syndrome (IBS). IBS is a common gastrointestinal disorder that affects 1 in 7 adults and is characterised by symptoms that are not explained by other disorders such as coeliac disease and inflammatory bowel disease. The most common symptoms of IBS include; stomach pain, bloating, wind, diarrhoea, constipation and nausea.

These symptoms can lead to stress and anxiety and affect our quality of life. The exact cause of IBS is not completely understood, however there are a number of things that may trigger symptoms.

The dietary cause of the symptoms associated with IBS is largely due to a group of carbohydrates called FODMAPs. This is an acronym which stands for;

  • Fermentable

  • Oligosaccharides

  • Disaccharides

  • Monosaccharides

  • And Polyols

Examples of FODMAPs include fructose, lactose, fructans and sorbitol. These carbohydrates, or sugars, can be poorly absorbed in the small intestine and fermented or broken down in the large intestine. This produces gas which leads to the symptoms associated with IBS. FODMAPs are also small and increase the amount of water delivered throughout the gut. This is called an osmotic effect. The gas produced by the large intestine in combination with this osmotic effect can cause changes to our gut motility or it’s movement. This can result in the symptoms of constipation and/or diarrhoea.

FODMAPs are found in many common foods including fruit, vegetables, grains and dairy. Although these carbohydrates are poorly absorbed in everyone, they are believed to affect and cause symptoms in people with conditions such as IBS as their guts are more sensitive. It’s important to remember that FODMAPs are not the cause of IBS, however limiting these in the diet can help control IBS symptoms.

Did you know that a low FODMAP diet can help improve gut symptoms in up to 75% of people with IBS?

In order to follow a low FODMAP diet it is vital that you plan ahead as the diet can be quite restrictive and involves a number of changes to your diet. This means that you are more at risk of nutrient deficiencies. Therefore, it is recommended that the FODMAP diet be completed under the supervision on an Accredited Practising Dietitian (APD) as they are able to provide you with appropriate low FODMAP substitutes to your favourite foods while ensuring you are getting all the nutrition you need with a healthy, balanced diet and a wide variety of foods. Studies also show that those with IBS who follow the low FODMAP diet with the assistance of an APD can get better relief from their symptoms.

The 3 Phases of the FODMAP Diet

There are 3 phases to the FODMAP diet.

Phase 1 – Low FODMAP or Elimination Phase.

This usually occurs over 2-6 weeks. This phase of the diet requires people to avoid any high FODMAP foods and substitute these with low FODMAP alternatives. Restricting high FODMAP foods enables us to determine if someone is responding to the low FODMAP diet and whether it is resulting in a decrease in their IBS symptoms.

The low FODMAP diet can be restrictive and people often struggle with the amount of variety in their diet and also flavour. FODMAPs also contain fibre and are natural prebiotics, so those on a low FODMAP diet can struggle with meeting their fibre requirements which can lead to constipation. So, a big consideration is the long-term consequences of a low FODMAP diet. And this is one of the reasons why it is only recommended for a short period of time of 2-6 weeks.

Phase 2 – Reintroduction or Challenge Phase

This usually takes around 6-8 weeks to complete. This phase involves the challenging or reintroduction of each of the FODMAP groups in a systematic way that is well planned to ensure that the results you get are clear and accurate. During this phase people continue to follow the low FODMAP diet as their base diet, with each FODMAP group being challenged one at a time. A dietitian will give advice and guidance on which food to use for challenging, the order to reintroduce them and also the amount.

This phase helps to determine if FODMAPs may be triggering a person’s symptoms. It not only helps to identify which FODMAPs may be triggering a person’s symptoms, but also how much. This is a particularly important part of the diet as it will identify whether a person may be able to have a particular FODMAP or tolerate a small, medium or large amount of a FODMAP before getting symptoms.

Phase 3 – FODMAP Personalisation

This is where different FODMAP groups are added back into the diet based on the results from a person’s challenges. This phase is a particularly important phase of the FODMAP diet as it enables us to develop a long-term balanced diet to ensure people are able to maintain a healthy gut to improve their overall health and quality of life.

Expert Tips for Phase 1

My expert tips to follow during the elimination phase of the FODMAP diet are;

  1. Find a low FODMAP substitute for any high FODMAP foods in the diet so that those following the diet can still enjoy all the meals they love.

  2. Include foods from all 5 food groups to make sure that all nutritional requirements are met and to decrease the risk of developing a nutrient deficiency.

Strategies to add flavour without adding high FODMAP foods are also important. My expert tips are:

  1. Use spices or herbs like basil, chili, cumin, ginger, pepper, rosemary or thyme on meat, fish, chicken, or vegetables.

  2. Use maple syrup instead of honey to sweeten baked goods or cereal.

  3. Avoid flavouring foods with onion or garlic powder.

  4. Drink water, regular or decaffeinated coffee or black tea instead of herbal teas and fruit drinks or juices.

Expert Tips for Phase 2

The main thing that I hear clients struggle with and are concerned about during this phase of the FODMAP diet is managing a potential flare up of their symptoms during the challenges. My expert tips to help with this are:

  1. Take time to relax. This can include relaxation tapes, yoga, or massage as these may help improve gut symptoms.

  2. Participate is regular exercise such as walking, cycling, swimming.

  3. Take time when eating meals and make sure food is chewed well. Eating fast can result in us swallowing more air which can lead to symptoms such as bloating.

  4. Keep a food and symptom diary during each of the FODMAP challenges to help identify which FODMAPs caused symptoms.

  5. Using hot packs is also a great option to help improve gut symptoms.

Expert Tips for Phase 3

As the name suggests, this personalisation phase is individual for everyone. My expert tips to follow during the personalisation phase of the FODMAP diet are;

  1. Let the results of the challenge phase guide the order in which each FODMAP is reintroduced back into the diet.

  2. Reintroduce foods that were well tolerated first.

  3. Try not to become disheartened if symptoms are experienced. Some gut symptoms from time to time are quite normal. We only need to become concerned if our symptoms are staring to impact on our ability to do our usual activities and quality of life.

  4. Keep track of any symptoms that may be experienced. It can be helpful to rate symptoms on a scale of 1-10, with 1 being no symptoms and 10 being severe symptoms.


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  1. Gandy J & the British Dietetic Association. Manual of Dietetic Practice–Fifth Edition. 2014: 460-466.

  2. Gibson PR, Shepherd SJ (2010). Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach. Journal of Gastroenterology and Hepatology. 25: 252–258.

  3. Monash University. The 3 steps of the FODMAP diet [Internet]. Cited 2019 April 22. Available from:

  4. Monash University. Monash University Low FODMAP DietTM Application for Android. Cited 2019 April 22.

  5. National Institute for Health and Care Excellence (NICE) (2008). Irritable bowel syndrome in adults: Diagnosis and management of irritable bowel syndrome in primary care. CG61.

  6. Tuck C & Barrett, J (2017). Re-challenging FODMAPs: the low FODMAP diet phase two. Journal of Gastroenterology and Hepatology. 32 (Suppl 1): 11–15.


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