By Dr. Jane Smith · Published October 26, 2026 · 13 min read
The FODMAP diet, usually called the low-FODMAP diet, is a short-term, three-phase eating plan that pins down which poorly absorbed carbohydrates trigger your irritable bowel syndrome (IBS) symptoms. You swap high-FODMAP foods for low-FODMAP ones for 2–6 weeks, reintroduce each FODMAP group one at a time, then keep limiting only the ones that cause trouble. It was developed at Monash University in Australia, and it has more trial evidence behind it than any other diet for IBS.
This guide covers what FODMAPs are, who the diet helps and who should skip it, how each phase works, a food list by group, the portion sizes that decide whether a food is "low" or "high", and a sample day. If you would rather start from a ready-made week of meals, our IBS-friendly meal plan lays out seven days.
Important
Medical Disclaimer
This article is for informational purposes only and is not medical advice. Rectal bleeding, black or bloody stools, anemia or weight loss you can't explain need a doctor's assessment before any diet change. The low-FODMAP diet works best with a registered dietitian, and it is not suitable for anyone with a current or past eating disorder.
What Is the FODMAP Diet?
The FODMAP diet temporarily limits a group of short-chain carbohydrates that the small intestine absorbs poorly. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. In the small intestine these carbohydrates draw in water; in the large intestine, gut bacteria ferment them and produce gas. Both stretch the bowel wall, which a sensitive gut registers as pain and bloating, as Monash University explains.
Everyone's gut does this. The difference in IBS is sensitivity. In MRI studies summarized in a 2024 review by Monash researchers and colleagues, FODMAPs caused similar water and gas responses in healthy people and people with IBS, but only the IBS group had exaggerated symptoms. That is why FODMAPs are not "bad" foods: most people digest them without a problem.
The approach was first published in 2005 and has since settled into a three-phase protocol: restrict, reintroduce, personalize. The restriction is a diagnostic tool, not a destination.
The FODMAP Groups and Where They Hide
| FODMAP | Type | Common sources |
|---|---|---|
| Fructans | Oligosaccharide | Wheat, rye, barley, onion, garlic |
| Galacto-oligosaccharides (GOS) | Oligosaccharide | Beans, lentils, chickpeas and other legumes |
| Lactose | Disaccharide | Milk, yogurt, soft cheeses, ice cream, custard |
| Excess fructose | Monosaccharide | Honey, apples, mango, high-fructose corn syrup |
| Sorbitol and mannitol | Polyols | Stone fruit, mushrooms, and sugar-free gum or mints sweetened with sorbitol, mannitol, xylitol or maltitol |
Sorbitol and mannitol are tested separately during reintroduction, so the protocol works with six groups in total. People rarely react to all six, which is the whole point of testing them one by one.
Who the Low-FODMAP Diet Is For
The low-FODMAP diet is for adults with diagnosed IBS whose bloating, pain, gas, diarrhea or constipation hasn't settled with basic eating changes (our guide on how to reduce bloating covers those first steps). IBS is common: about 12% of people in the US have it, and women are up to twice as likely as men to develop it, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
No IBS diet has more evidence behind it. In Monash's controlled crossover trial in 30 people with IBS, overall symptom scores on a low-FODMAP diet were about half those on a typical Australian diet: 22.8 versus 44.9 on a 100 mm scale, over 21 days. Bloating, pain and wind all improved. The American College of Gastroenterology's 2021 IBS guideline recommends a limited trial of the diet to improve overall symptoms, and Monash's own research finds that about 3 in 4 people with IBS respond.
Note
What the Research Shows
A 2025 network meta-analysis in The Lancet Gastroenterology & Hepatology pooled 28 randomized trials (2,338 patients) of 11 diets for IBS. The low-FODMAP diet had by far the most trials behind it (24), cut the risk of global symptoms not improving to about half that of a habitual diet (relative risk 0.51), and was the only diet tested in more than one trial that beat a habitual diet for bloating.
The evidence has limits. An earlier meta-analysis in Gut of 13 trials (944 patients) ranked the diet first for every symptom studied, but noted that most trials ran in specialist clinics and didn't measure the effect of reintroduction and personalization. Researchers are also testing the diet for IBS-like symptoms in inflammatory bowel disease in remission, in endometriosis and in older adults with chronic diarrhea, where the evidence is still thin.
Who Should Skip It or Get Help First
The full diet is restrictive and fiddly, and the 2024 Monash review lists groups for whom it is unsuitable:
- People with a current or past eating disorder
- People who are underweight or losing weight without trying
- People already on a restricted diet, such as a vegan diet
- Frail older adults and young children
- People with little time, interest or skill for cooking
For milder symptoms, or during pregnancy and breastfeeding, dietitians may use a FODMAP-gentle version that cuts only the most concentrated sources, such as wheat and rye bread and pasta, onion, leek, cauliflower, mushroom, apple, pear, stone fruit, cow's milk and legumes. It hasn't been tested in trials yet.
Get a diagnosis first. The NIDDK lists anemia, rectal bleeding, black or bloody stools and weight loss as signs that something other than IBS may be going on. The ACG also suggests a blood test for celiac disease when IBS comes with diarrhea, and because phase 1 cuts most wheat, have that test before you start: cutting gluten can affect celiac test results.
The 3 Phases of the FODMAP Diet
The diet runs in three phases: a short low-FODMAP phase to calm symptoms, a reintroduction phase to find your triggers, and a long-term personalized phase. Only the first is strict, as Monash's three-step guide sets out.
| Phase | How long | What you do | Goal |
|---|---|---|---|
| 1. Elimination | 2–6 weeks | Swap high-FODMAP foods for low-FODMAP ones | Get symptoms under control |
| 2. Reintroduction | 6–12 weeks | Test one FODMAP group at a time over 3 days, on a low-FODMAP background | Learn which groups you tolerate |
| 3. Personalization | Long term | Bring back tolerated foods; limit only your triggers, only as much as needed | The least restrictive diet that keeps symptoms down |
Phase 1: Elimination (2–6 Weeks)
In phase 1 you replace high-FODMAP foods with low-FODMAP alternatives for 2–6 weeks. Monash calls it a substitution diet rather than an elimination diet: an orange instead of an apple, chives instead of onion, lactose-free milk instead of regular milk. The aim is a varied plate, not a short list of "safe" foods.
How low is low? In the Monash crossover trial, the target was under 0.5 g of FODMAPs per meal. You don't need to calculate that yourself: lab-tested food ratings and their low-FODMAP serves (see the portion section below) do that work for you.
Phase 2 only makes sense if phase 1 worked. If your symptoms haven't improved after six careful weeks, staying on the diet longer is unlikely to help. Return to your usual foods and ask your doctor about other options.
Phase 2: Reintroduction (6–12 Weeks)
Phase 2 tests each FODMAP group on its own while the rest of your diet stays low-FODMAP. Monash's protocol challenges six groups separately (fructose, lactose, sorbitol, mannitol, fructans and GOS), each with a food high in only that one FODMAP. Monash uses mango to test excess fructose, for example. A typical challenge, from Monash's reintroduction tips, runs like this:
Day 1
Day 2
Day 3
Washout
Write down what you ate, how much, and how you felt each day. Our printable food diary template has portion and notes columns you can use as a symptom log. Expect this phase to take 6–12 weeks: Monash's 2020 guidance estimated 6–8 weeks, and its current info sheet allows 8–12. A dietitian helps choose test foods and portions and read reactions that aren't clear-cut.
Phase 3: Personalization (Long Term)
Phase 3 is your everyday diet: you eat the FODMAPs you tolerated freely and limit the ones that triggered symptoms, only as much as you need to. Monash notes that most people can bring back many high-FODMAP foods, if not as often or in the same amounts as before.
The long-term picture is encouraging. In a King's College London follow-up of 103 patients, satisfactory symptom relief rose from 12% at baseline to 61% after FODMAP restriction, and held at 57% after reintroduction. Most (82%) kept an adapted low-FODMAP diet, and their nutrient intake was not compromised. Tolerance can change, so retest foods that failed every few months.
High-FODMAP and Low-FODMAP Foods by Group
The table lists common high-FODMAP foods and low-FODMAP swaps from Monash University's 2026 food list. It is a sample, not the full database: ratings depend on portion size (next section), and Monash retests foods over time, so check its current app for anything not listed.
| Food group | High FODMAP (limit in phase 1) | Low-FODMAP swaps |
|---|---|---|
| Vegetables | Artichoke, asparagus, garlic, green peas, leek, mushrooms, onion, red bell pepper | Eggplant, green beans, bok choy, green bell pepper, carrot, cucumber, lettuce, potato, bean sprouts, zucchini |
| Fruit | Apples, apple juice, cherries, dried fruit, mango, nectarines, peaches, pears, plums, watermelon | Cantaloupe, green kiwifruit, mandarin, orange, pineapple, strawberries, blueberries |
| Dairy and alternatives | Cow's milk, yogurt, ice cream, custard, evaporated and condensed milk, soy milk made from whole soybeans | Lactose-free milk and yogurt, almond milk, soy milk made from soy protein, hard cheeses, brie, camembert, feta |
| Protein | Most legumes, some marinated and processed meats | Eggs, firm tofu, tempeh, plain cooked meat, poultry and seafood |
| Breads and cereals | Wheat, rye and barley breads, breakfast cereals, cookies, crackers and snack foods | Oats, quinoa, rice, corn or quinoa pasta, plain rice cakes, spelt sourdough, wheat-free breads |
| Sweeteners | Honey, high-fructose corn syrup, sugar-free candy | Table sugar, maple syrup, rice malt syrup, dark chocolate |
| Nuts and seeds | Cashews, pistachios | Macadamias, peanuts, walnuts, pumpkin seeds |
Two things surprise most beginners. First, wheat is limited for its fructans, not its gluten, which is why spelt sourdough makes the low list. Monash stresses that a strict gluten-free diet is only needed for celiac disease; if that is you, our gluten-free meal plan is the better starting point. Second, plain meat, fish, eggs and tofu are low-FODMAP, but marinades and processed meats often bring onion, garlic or wheat back in, so read ingredient lists.
Tip
Keep the Flavor of Onion and Garlic
Fructans dissolve in water but not in fat, so oil infused with garlic or onion carries the flavor without the fructans, according to Monash. The garlic or onion pieces themselves are still high-FODMAP, so strain them out, and don't rely on this in soups or stews, where fructans leach into the liquid. The green tops of spring onions and chives are low-FODMAP substitutes too.
Portion Sizes: When a Low-FODMAP Food Turns High
Most foods are not simply high or low FODMAP; the portion decides. Monash compares lab results for a typical serve (75 g for most vegetables) against its cut-offs, and a food can move from green to amber or red as the serve grows. A 2022 review in Nutrients puts it plainly: outside a few very concentrated foods, portion size is what decides whether a food counts as low or high.
The table shows low-FODMAP serves of fiber-rich staples, including two legumes that are off the menu in larger amounts.
| Food | Low-FODMAP serve | Fiber per serve |
|---|---|---|
| Rolled oats, uncooked | 1/2 cup (52 g) | 5 g |
| Quinoa, cooked | 1 cup (155 g) | 3 g |
| Brown rice, cooked | 1 cup (180 g) | 3 g |
| Canned chickpeas, drained | 1/4 cup (42 g) | 2 g |
| Green lentils, boiled | 1/4 cup (23 g) | 1 g |
| Broccoli, raw | 3/4 cup (75 g) | 3 g |
| Banana, unripe | 1 medium (100 g) | 2 g |
| Green kiwifruit, peeled | 2 small (150 g) | 6 g |
| Almonds | 10 nuts (12 g) | 1 g |
| Walnuts | 10 halves (30 g) | 2 g |
| Chia seeds | 2 tbsp (24 g) | 8 g |
| Firm tofu | 2/3 cup cubed (160 g) | 6 g |
Serves and fiber values are from Monash University's 2021 list of low-FODMAP fiber sources.
Several low-FODMAP serves at one meal are usually fine. Monash set its cut-offs conservatively for exactly that reason, and its guide to FODMAP stacking says not to worry about combining foods while your symptoms are controlled. If they aren't, spacing meals and snacks 2–3 hours apart can help.
Fiber is the nutrient most likely to slip, because many high-FODMAP foods are also high-fiber foods. Adults need 22–34 g a day, and Monash notes that Americans average only 16 g even before cutting anything. Soluble fiber seems to be the most helpful type for IBS, and our soluble fiber foods guide lists the best sources.
A Sample Low-FODMAP Day
This day uses only foods from the low-FODMAP lists above, at Monash's low-FODMAP serves. Size the plain protein to your appetite.
Sample low-FODMAP day
- Breakfast: 1/2 cup rolled oats cooked with lactose-free milk, topped with 5 strawberries, 2 tbsp chia seeds and a little maple syrup
- Lunch: 1 cup cooked quinoa with grilled chicken, cucumber, lettuce and crumbled feta, dressed with garlic-infused olive oil
- Snack: 2 small mandarins and 10 almonds
- Dinner: Baked salmon with 1 cup brown rice, 15 green beans and a carrot, finished with chives and spring onion greens
- Evening: Lactose-free yogurt with 10 walnut halves
Notice what isn't missing: grains, fruit, dairy, nuts and vegetables all stay on the plate. That variety matters, because fiber and calcium are among the nutrients a strict low-FODMAP diet can squeeze out.
Why the FODMAP Diet Isn't a Weight-Loss Diet
The low-FODMAP diet is a short-term medical diet for IBS symptoms, not a way to lose weight. Monash's own dietitians write that it should not be followed for weight loss, and that restrictive diets can cause weight loss people don't intend, which is a reason to see a dietitian, not a result to chase.
Weight follows calories, not FODMAP content. Swapping wheat bread for spelt sourdough, or honey for maple syrup, changes the FODMAP content, not the kind of food: bread is still bread and sugar is still sugar. If you want to lose weight on purpose, a moderate calorie deficit works with any food list, including a personalized low-FODMAP one. And if you suspect phase 1 has quietly shrunk your meals, Caloria, the AI calorie tracker, logs a meal from a photo and shows its calories and protein, so you can see whether your intake has dropped.
Staying strict for months also has costs:
- Gut bacteria. A meta-analysis of nine trials found three that reported fewer bifidobacteria after the diet. Monash notes that some FODMAP-rich foods feed beneficial bacteria, which is one reason it calls the diet not a lifetime diet. Our guide to probiotics for gut health covers what those bacteria do.
- Nutrients. A strict low-FODMAP diet can compromise intake of fiber, calcium and B vitamins, according to Monash.
- Cost and social life. In the King's College follow-up, people who kept restricting reported higher food costs and more disruption to social eating.
What If the Low-FODMAP Diet Doesn't Work?
About 1 in 4 people with IBS don't respond to the low-FODMAP diet. If that is you, go back to your usual diet rather than cutting more foods, which only adds to the risks above.
The diet is one of several evidence-based IBS treatments. The ACG guideline also suggests gut-directed psychotherapy for overall IBS symptoms and recommends specific medicines for IBS with constipation or diarrhea. These are worth discussing with your doctor or gastroenterologist.
The Goal Is the Fewest Restrictions That Work
The FODMAP diet succeeds when you end up eating more foods, not fewer. Keep the strict phase to six weeks or less, test each group one at a time, and treat the result as a short personal list of triggers and portions rather than a list of forbidden foods.
Work with a dietitian if you can, use a lab-tested food guide, and keep notes through reintroduction: the symptom log is what turns a restrictive diet into one that fits your gut.