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Does portion size matter on a low-FODMAP diet?

Does portion size matter on a low-FODMAP diet?

Portion sizes are important on a low-FODMAP diet because some low-FODMAP foods become high FODMAP at larger serving sizes and can cause unwanted symptoms.

Why is portion control so important on a low-FODMAP diet?

Portion sizes are crucial on a low-FODMAP diet. Just because a food is classed as low FODMAP doesn’t mean you can eat it in unlimited quantities, and some high-FODMAP foods are safe to eat in small portions. The goal of a low-FODMAP diet is to reduce the overall level of FODMAPs – it’s not a FODMAP-free diet (Muir, 2015).

Where do you find information on low-FODMAP portion sizes?

The Monash University Low FODMAP app or Monash University Low FODMAP booklet contain lists of low-FODMAP foods with recommended safe serving sizes. Every person has a different tolerance level to FODMAPs, which may mean you can tolerate a little bit more or less than the recommended serving size (Muir, 2015; Scarlata, 2015). You will be able to work out your own tolerance levels over time.

How do you use the traffic light system in the Monash University app?

The Monash University app uses a simple ‘traffic light’ system to organise foods based on FODMAP levels for a typical serving size of that food (Muir, 2015). Green is low FODMAP, orange is moderate FODMAP and red is high FODMAP (Muir, 2015). You need to click on each food in the app to find out what the recommended serving size is. Be careful as some low-FODMAP foods become high FODMAP if you go over the recommended portion (Muir, 2015). It’s also important to explore red-rated foods as some of them do have a smaller low-FODMAP serving size (Muir, 2015).

For example:

  • Sweet potato (kumara) is high FODMAP if you have 1 cup (4.94 oz or 140g). However, a smaller serving of 1/2 cup or (2.74oz or 70g) is considered low FODMAP (Monash University App, 2014).
  • Oats are only low FODMAP at a 1/4-cup portion (dry measurement before cooking). If you consume a 1/2-cup portion (dry measurement before cooking) then you will consume moderate levels of FODMAPs (Monash University App, 2014).
  • Broccoli is considered low FODMAP at a 1/2-cup (1.66oz or 47g) serving size. However, 1 cup is considered high FODMAP (Monash University App, 2014).

While in the elimination phase of the diet, it’s recommended that you avoid red-rated serving sizes and foods, limit orange-rated serves, and focus on eating mainly green-rated foods at the recommended serving sizes (Muir, 2015).

How many different low-FODMAP foods can you have in each meal?

Low-FODMAP recommended serving sizes have been developed based on typical serving sizes of that particular food per meal (Muir, 2015). This means you can eat a number of different green-rated foods per meal. If you’re feeling hungry, add another ‘green’ vegetable to your meal. I recommend weighing low-FODMAP vegetables and fruit before cooking to make sure you stay within the recommended serving sizes.

If you want to eat more than the recommended serving size for a low-FODMAP food then you need to check the additional information provided with each food listing. Some low-FODMAP foods will become high FODMAP at larger serving sizes, while others will remain safe to eat in bigger serves (Muir, 2015Scarlata, 2015).

Registered dietitian Kate Scarlata recommends adding a few more bites of rice or white potatoes if you’re feeling hungry as these foods are very low FODMAP (Scarlata, 2015).

Can you eat the same food multiple times in a day?

If you stick to the recommended low-FODMAP serving size and leave a few hours between each serve, it’s okay to eat the same food a couple of times a day (Scarlata, 2015).

Do meats and other sources of protein contain FODMAPs?

Chicken, fish, red meat and eggs are protein-based foods that are FODMAP free (Monash University App, 2014Scarlata, 2015) so if you’re hungry you can eat slightly larger portions of these naturally FODMAP-free foods (Scarlata, 2015).

What are the portion control rules around fruit?

According to Dr Sue Shepherd (the creator of the low-FODMAP diet), you should not eat more than one serve of ‘suitable’ fruits at each meal or sitting (Shepherd, 2011). One serve normally equals about one metric cup of cut-up fruit, or one whole piece of fruit such as a medium banana or medium orange (Monash University App, 2014Shepherd, 2011). You can enjoy as many serves of fruit per day as you like – but leave two to three hours between each serve (Shepherd, 2011).

Final thoughts

The Monash University Low FODMAP app is a great resource for low-FODMAP serving sizes. You can eat multiple green-rated foods for each meal and you can repeat the same foods throughout the day. If you are repeating foods, leave a few hours in between each serve. When it comes to fruit, remember to have one serve at a time and leave two to three hours between each serve. If you need guidance, make sure you consult a FODMAP-trained dietitian to help you find your own tolerance levels.



Original article sourced from https://www.alittlebityummy.com/blog/does-portion-size-matter-on-the-low-fodmap-diet/

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Muir, J. Talking About the Traffic Light System. Monash University Low FODMAP Blog. 2015-02-05. Retrieved on 2015-07-12.

Scarlata, K. Portion Size Matters on the Low FODMAP Diet. Well Balanced. 2015-04-28. Retrieved on 2015-07-12.

Monash University App. Food Guide. The Monash University Low FODMAP Diet App. 2014: Edition 4. Date retrieved: 2015-03-05. Accessed 2015-03-05.

Shepherd, S. Food, FODMAPs and IBS: What to eat and what to avoid. Healthy Food Guide. 2011-11-09. Retrieved on: 2015-03-10.


Alana Scott creates delicious low-FODMAP recipes to help people live a healthy life on a low-FODMAP diet. In 2013, Alana was diagnosed with Irritable Bowel Syndrome (IBS) and has battled with a chronic immune system disorder since the age of 12. Alana is also coeliac, allergic to nuts and intolerant to dairy products, so she understands first-hand how difficult it can be to cook for and live with multiple food intolerances. These experiences inspired Alana to set up A Little Bit Yummy. Follow her online: A Little Bit Yummy, Pinterest, Google+, Facebook or on Instagram: alittlebityummy

Disclaimer: A low-FODMAP diet is a specialised medical diet that should be trialled under the guidance of a professional dietitian, who will help you to find your personal tolerance levels for each FODMAP group. It is not appropriate for healthy individuals with no gastrointestinal disorders to follow a strictly low-FODMAP diet. If you are concerned or have questions, talk to your medical practitioner.

First published: Oct 2015

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