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FODMAPS, Part 2: Applying the Diet


My last post introduced what FODMAPs are and why an athlete may be interested in pursuing the diet.

Now it’s time to cover how one would apply FODMAPs to their life. Part 3 of this series will be an in-the-weeds post for the science nerds.

A Registered Dietitian Begins with a Dietary Assessment

Athletes are the experts of their own bodies, so have an honest, detailed conversation about what they already know about their eating habits and symptoms.

A full dietary assessment may provide clues surrounding foods the athlete avoids and why, diagnosed food allergies and medical conditions, symptoms and their patterns (e.g., time of day, while exercising), prescription medications, supplements, frequency and texture of bowel movements, etc.

After a thorough assessment, the dietitian evaluates if the athlete has:

  1. An idea of the trigger food(s) that lead to symptoms: If so, jump to “Plan A” below.

  2. No clue what’s causing their symptoms: Jump to “Plan B”.

  3. No clue what’s causing their symptoms and isn’t keen on following a methodical, detail-oriented plan: Jump to “Plan C”.

For all three plans:

  • Symptoms need to be tracked against baseline measurements: For example, prior to beginning FODMAPs the athlete reports painful abdominal distension as an 8 on a scale of 1-10 (1 being no symptoms and 10 being severe). If the athlete is compliant following a low-FODMAPs diet for a couple of weeks and their symptoms decrease to a 2 or are nonexistent, we know we’re on the right track. Depending on how their bowel movements are affected, you could also have the athlete use the Bristol Stool Chart (see below).

  • Restricted foods need to be substituted for: This isn't your typical restrictive diet. If you’re removing cow’s milk due to the lactose (i.e., disaccharide group) then replace with lactose-free milk to ensure the athlete is still receiving calcium, vitamin D, and protein.

  • The challenge phase is difficult: Work with a registered dietitian who is knowledgable about the topic while accounting for the athlete's nutritional needs. For instance, a vegan may have a difficult time meeting their protein goals while beans and legumes are restricted [e.g., high in both fructans and galacto-oligoscaccharide (GOS)].

  • Following low FODMAPs may not lead to complete avoidance of symptoms—and does not “cure” them: If the athlete doesn’t follow their FODMAP-appropriate diet then symptoms will return. Plus, the gut is an evolving organ and what may be tolerated today may not be tolerated five years from now. It’s important to communicate this with the athlete up front as to manage their expectations.

  • Loop the athlete's doctor in: Nutrition is part of a tool box, not the cure, for minimizing symptoms. I’ll request that the doctor initially meets with the athlete to ensure a potential medical condition isn’t going unchecked, and is the real culprit (e.g., Celiac disease).

The diet's purpose is to find the most inclusive combination of low-, moderate-, and high-FODMAP items to promote variety and a nutritionally-balanced diet. Ultimately, you're creating a long-term diet for the athlete to follow.


Different Plans for Different Athletes

Plan A. The Informed Athlete: A Modified Low FODMAPs Approach

What's nice about this plan is how non-restrictive it is. You're upfront about acknowledging the athlete's insight regarding their symptoms, which could help with buy in.

  1. Go low with the FODMAPs that are known to cause symptoms for this athlete: One would think an athlete is already doing this, but you’d be surprised. Plus, there may be more aggravators within a group that may be unaccounted for. Have the athlete track their symptoms and if they’re consuming FODMAPs of concern. Depending on the athlete’s motivation, I may have them track their food intake, the time consumed, and any ensuing symptoms for at least four days. Included would be a rest, hard training, easy training, and weekend day, plus their training schedule and what they’re consuming during exercise (e.g., high-fructose sport gels).

  2. Review symptoms: If they persist and are unbearable, even when the athlete was compliant with the modified FODMAPs diet, review their food intake and symptoms to highlight patterns of other problematic items. You may need to trial Plan B, Step 3, or connect with a gastroenterologist.

  3. Create a modified FODMAPs diet for the athlete to follow: Continue to have them monitor their symptoms, even if it's simply daily reflection and not a written food and symptom record.

Plan B. Starting from Scratch: A True Low FODMAPs Approach

  1. Low FODMAPs across all five groups for 2-6 weeks: This restrictive phase is followed until severe symptoms are consistently weakened. This is where baseline measurements are helpful to compare against.

  2. After 2-6 weeks, meet with a registered dietitian to review symptoms and dietary compliance: If symptoms are not improving and compliance occurred, this is when I would refer to a gastroenterologist, since continuing to restrict food isn’t helping and the low FODMAPs diet should be stopped. At the 2-6-week mark, and if symptoms are less severe, the next step is undertaken.

  3. Reintroduce FODMAPs by group to determine the culprit(s) (see below flowchart):

  • Maintain a background low-FODMAPs diet and reintroduce a “high” item from one group at a time (see table 1 in this paper), in small doses, and over the period of at least three days.

  • Avoid reintroducing multiple groups at once, since if symptoms flare up it’s hard to tell what group(s) is causing them.

  • If the athlete’s symptoms worsen with small portions, return to the background diet for a 2-3-day washout period. The washout allows the flared-up symptoms to calm down prior to trialing a new group.

  • If the athlete’s symptoms aren’t flaring up, increase the dose, and possibly the frequency, of the trial food.

  • Continue the process of reintroducing groups, one at a time, with a washout period in between group trials, until all groups have been accounted for.

  1. Finally, once the dietitian has figured out what groups are triggers or safe, they will create a personalized, modified FODMAPs plan for the athlete.


Plan C. Starting from Scratch: Modifying the True Low FODMAPs Approach

Plan B is systematic and detail-oriented—one that some athletes may find overwhelming or undoable. For them, it may be best to:

  1. Download the Monash University FODMAP App.

  2. Consume “green” foods for all FODMAP groups for 2-6 weeks (or until symptoms weaken or subside).

  3. Introduce “amber” foods per group to evaluate tolerance while following a background “green” FODMAPs diet.

  4. Allow for a wash-out period in between group challenges.

  5. Progress to “red” foods upon learning what groups are asymptomatic for them.

  6. Design a modified FODMAPs diet.

How Long Would an Athlete Remain on FODMAPs For?

Low FODMAPs isn’t meant to be forever. Why?

  • It’s a restrictive diet: Any time food groups are restricted, as are vital minerals, vitamins, and nutrients. Plus, eating in social settings and at restaurants may become negative experiences, or avoided, due to the fear of not having low-FODMAP options available.

  • It’s sometimes unneeded: If it’s found in the initial appointment that an athlete is only sensitive to fructans, there’s no need to restrict everything else until symptoms tell you otherwise.

  • It’s low in prebiotics: Prebiotics are the food supply in the gut for probiotics, so if you can’t feed the probiotic bacteria then they begin to die. Prebiotics are found in the fructans and GOS groups and, after 3-4 weeks of avoidance of them, have shown changes to the colonic microbiota. Even if high-fructan items are discovered to be problematic, including small amounts in the athlete’s daily diet may still be necessary and health promoting.

My Application with Collegiate Athletes

This population doesn’t always have absolute control over what foods are available to them. At school, they eat what’s at the fueling station or in the dining hall—including unchecked ingredients in meals. When traveling with their team, an athlete may have no other option than to eat high-FODMAP airport food, hotel breakfasts, or at restaurants for a post-game meal. They have to eat something!

Given the reality of the athlete’s lack of control, I don’t typically ask them to go 100% low FODMAPs from the beginning. I'm also careful if the athlete has a known history of disordered eating or an eating disorder, since any food recording or increased focus on their diet may be a trigger.

Athletes who have a kitchen, the financial resources, nutritional knowledge, and are willing to hit low FODMAPs full throttle could be great candidates for the traditional restrictive approach—especially if they have no clue what’s causing their symptoms (i.e., Plan B).

Further Reading:

If you're confused what FODMAPs stands for, read my blog on the diet's basics.

Discover more about food brands, where FODMAPs data from the food system comes from, and why the cumulative effect of low FODMAPs may matter.

Foods and beverages marketed to athletes contain FODMAP ingredients. Find out what products contain and are free of FODMAPs.

Barrett, J.S. (2017). How to institute the low-FODMAP diet. J Gastroenterol Hepatol,32(Suppl 1):8-10. doi: 10.1111/jgh.13686.

Kate is a leading dietitian and researcher in the area of FODMAPs. Her free resources include a low FODMAPs grocery list and a high- and low-foods list, both of which are helpful during the initial 2-6-week challenge phase.

“The Complete Low-FODMAP Diet” by Sue Shepherd, PhD and Peter Gibson, MD.

The book includes lists of low-, medium-, and high-FODMAP options, which is helpful during the challenge and modified diet stages. It also includes a library of recipes and is my go-to book when counseling symptomatic athletes.

The university that penned the term FODMAPs, and continues to lead research on the topic, created an app that allows users to filter by FODMAP subgroup—making it helpful during both the challenge and modified diet stages. The app has a one-time fee and is a tool I use when counseling.

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