Does Portion Size Matter on the Low FODMAP Diet?

Why is portion control so important on the Low FODMAP diet?

Portion sizes are crucial to getting good symptom control while on the low FODMAP diet. Just because a food is classed as low FODMAP it doesn’t mean you can eat unlimited quantities. Also, some high FODMAP foods are safe in small portion sizes. The goal of the low FODMAP diet is to reduce the overall level of FODMAPs to help you gain good symptom control, and it is not a FODMAP free diet (1).

Where do you find information on low FODMAP portion sizes?

The Monash Univeristy Low FODMAP Diet app or Monash University Low FODMAP booklet, both contain up-to-date lists of low FODMAP foods, and recommended safe serving sizes.

The recommended serving sizes are a great place to start. Just remember that every person has different tolerance levels to FODMAPs, which may mean you can tolerate a little bit more or less than the recommended serving size (1 2). You will need to find your own tolerance levels.

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

The Monash Low FODMAP Diet app organises foods by a traffic light system, based on the FODMAP levels for a typical serving size of that food per meal (1). Green is low FODMAP, orange is moderate FODMAP, and red is high FODMAP (1). You need to click on each food in the app to find out what the recommended serving size is. Make sure you read the notes under the suggested serving size, as some low FODMAP foods become high FODMAP if you go over the recommended portion (1). It is also important to explore red rated foods as some of them do have a smaller low FODMAP serving size (1).

For example:

Sweet potatoes are high FODMAP if you have 3/4 cup (112g). However, a smaller serving of ½ cup or 75g is considered low FODMAP (3).

Quick oats are only low FODMAP at a ¼ cup portion (dry measurement before cooking). If you consume a ½ cup portion (dry measurement before cooking) then you will consume moderate levels of FODMAPs (3).

Broccoli is considered low FODMAP at  ½ cup to 1 cup serves, depending on which part of the broccoli you are eating. However, notes in the app tell us that larger serves can become high FODMAP (3).

While in the first phase of the diet, it is recommended that you avoid red rated serving sizes of foods, limit orange rated serves, and focus on eating mainly green rated serving sizes and foods (1).

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

The low FODMAP recommended serving sizes have been developed based on typical serving sizes of that particular food per meal (1). This means you can eat a number of different green rated foods per meal, just make sure you stick to the recommended serving sizes (1). So if you are feeling hungry, add another green rated vegetable to your meal. I recommend weighing your low FODMAP vegetables and fruit before cooking, to make sure you are staying 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 (1 2).

For example, registered dietitian Kate Scarlata recommends adding a few more bites of rice or white potatoes if you are feeling hungry as these foods are very low FODMAP (2).

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

Providing you stick to the recommended low FODMAP serving size and leave a few hours between each serve, you should be okay to eat the same food a couple of times a day (2).

Do meats and other sources of protein contain FODMAPs?

Chicken, fish, red meat, and eggs are protein based foods that are FODMAP free (3 2). This means if you are feeling especially hungry you can eat slightly larger portions of these naturally FODMAP free foods (2).

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 per meal or sitting (4). One serve normally equals about one metric cup of cut up fruit, or one whole piece of fruit, such as one medium banana or medium orange (3 4). You can enjoy several serves of fruit per day as you like – but leave two to three hours between each serve (4).

Final Thoughts

The Monash Univeristy Low FODMAP Diet app is a great resource for low FODMAP serving sizes. Make sure you explore each food to find the recommended serving. 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 2 to 3 hours between each serve. If you need guidance, make sure you consult a FODMAP trained dietitian to help you find your tolerance levels. For more helpful tips you can follow us on Facebook or sign up for our weekly newsletter. Happy Eating!