Why Do Portion Sizes Matter with Low FODMAP Foods?

When it comes to FODMAPs, the professionals don’t label foods as simply “high” and “low”. While that may seem easiest, FODMAPs are a bit more complicated than that. Foods contain different amounts of FODMAPs and therefore can be “safe” at one serving size, but cause problems at another.

With the low FODMAP diet, it is common to believe that we are aiming for absolutely no FODMAPs in our diet. Not only is this untrue, but it’s actually unnecessary! The goal of this diet is to reduce the overall level of FODMAPs we consume, not completely avoid them. After all, we don’t call it a “FODMAP-free diet!”

Low FODMAP portion sizes

As a dietitian specializing in gut health, I explain this to my patients by comparing the gut to a bucket. Everyone has a different sized bucket, so can therefore tolerate different amounts of FODMAPs before having noticeable symptoms. I like to say that individuals with IBS have smaller buckets - but that doesn’t mean we can’t include FODMAPs strategically!

Most people on the low FODMAP diet can tolerate a fair amount of FODMAPs but do better when these foods are spaced throughout the day. This is why we encourage patients to stick to low FODMAP foods at the portions recommended by Monash University.

Where to learn about portion sizes

Researchers at Monash University work very hard to determine the FODMAP content in our foods. The Monash University low FODMAP diet app is a great resource when following the low FODMAP diet. In particular, the app is excellent for learning about FODMAP portion control, as it uses a traffic light system to rank FODMAP content in our foods based on serving sizes.

Not only does it tell us which foods are “red light” or likely to cause symptoms, but it also tells us whether we can tolerate a smaller amount of the food before it becomes problematic. For example, ½ a cob of corn contains low FODMAPs (green light). However, consuming 1 full cob of corn is considered high FODMAP and is therefore a no-go!

Adding up your low FODMAP foods

I am commonly asked by clients if there is a maximum number of low FODMAP foods they should be eating. Is it possible to overdo it with low FODMAP foods too?

The criteria set out by Monash University is that we can safely consume multiple low FODMAP foods per meal as long as we stick to the portion sizes recommended.

The truth is, this will change from person to person. Tolerance to FODMAPs is very individualized. Some people may notice that stacking multiple low FODMAP foods in one meal can still overwhelm the gut. However, the majority of my clients seem to do best when they stick to a variety of low FODMAP or “green light” foods at each meal. Many can even add one moderate or “yellow light” food as well - as long as they stick to the recommended portion!

It’s all in the timing

The recommended serving sizes provided by Monash University are meant to reflect the amount of each food that someone would typically eat per meal, not in an entire day. This tells us that we can actually consume a wide variety and amount of low FODMAP foods when we space them throughout the day!

In my practice, I also encourage people to try a few moderate FODMAP or “yellow light” foods in order to create more variety in their diets. As long as they stick to the recommended portion size per meal, most people do really well with this!

Eating more small, frequent meals and snacks can also help to prevent us from getting too hungry and potentially overeating later in the day - that’s when FODMAP portion control tends to go out the window.

Still hungry?

If you are still hungry but feel you have reached your upper limit for FODMAPs at a particular meal or snack, there are still plenty of foods you can fill up on!

To bulk up a meal, consider adding foods that contain virtually no FODMAPs like meat, fish, poultry, and eggs. Other great foods to bulk up a meal are rice and white potatoes, which are very low in FODMAPs as well. Don’t forget added fats, fat helps with satiety, and is a great way to add flavor to vegetables, meat marinades, and to top carbohydrates.

What you need to remember

As you can see, FODMAPs are complicated! There truly is no black and white answer to how much each person can tolerate. For this reason, it is highly recommended to work with a medical professional who specializes in the low FODMAP diet, such as a registered dietitian or doctor.

In my experience, the key to success with FODMAPs is understanding that we actually don’t need to be as restrictive as you may think! We can include a variety of low and even moderate FODMAP foods in our diets when we consider serving sizes, timing, and the overall quantity of food at each meal.

Lastly, remember that food is only one piece of a very large puzzle. Our IBS symptoms can also stem from other lifestyle factors such as stress, poor sleep habits, or the medications we take. And more often than not, it is a combination of these things. Keep this in mind as you continue on your journey to IBS management.