If you live with IBS, you know how frustrating it can be to feel like every meal is a guessing game. Bloating, abdominal pain, constipation, diarrhea, and gas can make eating stressful instead of enjoyable. The best evidence-based approach for managing IBS symptoms is the low FODMAP diet, and the first step is called the elimination phase.
As a dietitian specializing in IBS, I always emphasize to my clients that this is not a long-term diet but a short-term strategy designed to help calm the gut, reduce symptoms, and identify which foods are triggering their digestive discomfort.
In this article, I will discuss how the Low FODMAP diet works and explain the first step: the elimination phase.
Let’s dig in!
What Are FODMAPs?
Let’s start with the basics. Researchers at Monash University created the acronym “FODMAP” and developed the protocol for IBS relief.
The acronym stands for a group of fermentable carbohydrates that can be poorly absorbed in the gut:
- Fermentable
- Oligosaccharides (fructans and GOS)
- Disaccharides (lactose)
- Monosaccharides (excess fructose)
- Polyols (sorbitol, mannitol and perseitol)
In people with IBS, these carbohydrates can pull extra water into the intestines and ferment rapidly in the colon, leading to symptoms like bloating, abdominal pain, gas, diarrhea, and constipation.
Why the Low FODMAP Elimination Works
Research shows that the low FODMAP diet improves overall gut symptoms and quality of life in most people with IBS (1).
When high-FODMAP foods are reduced, there is typically less fermentation, less gas production, and less fluid drawn into the intestines. This can help decrease digestive symptoms like bloating, abdominal pain, and diarrhea/constipation and make it easier to identify personal food triggers later on.
Many people begin noticing improvement within 2–4 weeks, although response times vary. In my experience working with people with IBS, when the diet is followed correctly, it is very effective.
How Does The Low FODMAP Diet Work?
Firstly, the Low FODMAP diet is a 3-step process, and the elimination phase is only the first step.
During this phase, you reduce your intake of high-FODMAP foods with the goal of calming the digestive system and finding relief from IBS symptoms such as bloating, abdominal pain, gas, diarrhea, constipation, or a combination of both.
Once symptoms improve, the next step is the reintroduction phase, where high-FODMAP foods are systematically tested one group at a time. This helps identify your personal triggers and, just as importantly, the foods you do tolerate well.
From there, you move into the final stage: your personalized low FODMAP diet — the phase where you expand your diet as much as possible while still keeping symptoms under control.
This distinction matters because the goal of the low FODMAP diet is not lifelong restriction. The final goal is personalization: eating the widest variety of foods possible while still managing symptoms effectively. This will help you eat with more confidence, more flexibility, and far fewer symptoms.
The Low FODMAP Elimination Phase
I often explain to my clients that the low FODMAP diet elimination phase is not about perfection, restriction, or “clean eating.” It’s a temporary strategy aimed at reducing the FODMAP level of their diet and reducing (or even eliminating) their gut symptoms.
Here are 5 key things to know about the elimination phase.
1. It’s more about replacing than eliminating
Although the word elimination can make this sound like an extremely restrictive diet, the low FODMAP diet does not eliminate entire food groups.
Unlike diets that completely remove grains, carbohydrates, dairy, or legumes, the low FODMAP approach focuses more on strategic replacements. In practice, this means swapping high-FODMAP foods for low-FODMAP alternatives that are easier to digest.
For example:
- Instead of regular milk → lactose-free milk
- Instead of wheat pasta → rice or quinoa pasta
- Instead of garlic and onions → garlic-infused oil and green onion tops
There are certainly a few foods that need to be fully avoided during this phase — garlic and onions being the most common examples — but many foods simply need portion adjustments rather than complete elimination.
In fact, one of the biggest misconceptions about this diet is that you need to remove all FODMAPs completely. That’s not the goal. The objective is to lower the overall FODMAP load enough to reduce symptoms.
2. What foods do you need to restrict during the FODMAP elimination phase?
The fermentable carbohydrates that are restricting during the low FODMAP elimination fall into four main categories:
- Lactose: milk, yogurt, ice cream
- Excess fructose: honey, agave, high-fructose corn syrup, and fruits that contain too much fructose
- Polyols (sugar alcohols): certain fruits and vegetables, sugar-free gums and candies
- Oligosaccharides (fructans and GOS): wheat, onions, garlic, certain types of legumes (beans, lentils and dried peas), and some nuts like cashews and pistachios.
If you want to deep dive into each of the FODMAP groups, you can check out these articles:
FODMAP Explained: “F” stands for Fermentable
FODMAP Explained: FOS & GOS – Your Ultimate Guide to Oligosaccharides from an IBS Dietitian
FODMAP Lactose Explained: Understanding Disaccharides and IBS
FODMAP Explained: “M” Stands for Monosaccharides
FODMAP Explained: “P” Stands for Polyols
The good news is that there are still many foods you can enjoy during this phase, including:
- Animal proteins
- Grains and starches: rice, potatoes, oats, quinoa, millet
- Fats and oils
- Lactose-free or low-lactose dairy products
- Nuts and seeds: walnuts, pecans, almonds, chia, flax, pumpkin, sunflower seeds
- Many fruits and vegetables,
- Most herbs and spices
When I show my clients the full list of foods they can eat on the low FODMAP diet, their first reaction is usually surprise. Many realize the diet is far less restrictive than they initially thought based on the lists they found online. Unfortunately, a lot of online information about the low FODMAP diet is incomplete, oversimplified, or outdated, which can make the elimination phase feel much more limiting than it actually is.
3. The goal is to achieve adequate symptom relief
The purpose of the elimination phase is not perfection: it’s symptom improvement.
Research shows that most people who respond to the low FODMAP diet notice improvement within about 2–6 weeks.
For many people, this may look like:
- Less bloating
- Reduced abdominal pain
- More predictable bowel movements
- Less urgency or constipation
- Feeling more comfortable after meals
Once symptoms improve significantly, it’s time to move on to the reintroduction phase. Staying in elimination longer than necessary does not typically provide additional benefits and can actually make the diet more restrictive than it needs to be.
4. The low FODMAP diet elimination phase is temporary
This is one of the most important points to remember: the elimination phase is not intended to last forever.
Because this phase restricts many nutritious foods, staying on it long-term may reduce intake of important nutrients like dietary fiber and calcium. Research also suggests that prolonged restriction may negatively affect beneficial gut bacteria because many high-FODMAP foods are naturally rich in prebiotics.
If symptoms do not improve after about 6 weeks — especially when the diet has been implemented correctly — it’s important to reassess with a healthcare professional or dietitian. IBS symptoms are complex, and FODMAPs are not always the only factor involved.
5. This phase shouldn’t be more restrictive than it needs to be
One of the biggest pitfalls I see is people becoming overly fearful of foods during the low FODMAP diet elimination phase.
For example, many people assume they need to completely avoid gluten or dairy. But the low FODMAP diet is not a gluten-free diet or a dairy-free diet unless those foods specifically trigger symptoms.
You can still include:
- Lactose-free milk and yogurt
- Hard cheeses that are naturally low in lactose
- Some wheat products such as authentic sourdough bread
Similarly, fiber is incredibly important for gut health and bowel regularity, so avoiding all fiber-rich foods can often make constipation (or diarrhea) worse.
Unlike many people think, you can still maintain an adequate (or even optimal) fiber intake during the low FODMAP elimination phase. The key is choosing the right kind of fiber and slowly adjusting your intake.
Instead of becoming more restrictive, the goal is to build a diet that is still balanced, varied, and enjoyable while reducing symptoms.
Common Mistakes During the Elimination Phase
Staying in elimination for too long
One of the biggest misconceptions is that lower FODMAP always means healthier. In reality, the elimination phase is only intended to be temporary. Long-term restriction can unnecessarily limit food variety and may negatively affect quality of life and the gut microbiome.
Trying to do it alone
The diet can feel overwhelming at first because FODMAPs are found in many everyday foods and portion sizes and combinations matter. Working with a dietitian trained in the low FODMAP diet can make the process far more manageable, effective, and nutritionally balanced. A knowledgeable dietitian can help you adapt the diet to your lifestyle and preferences and make it feel doable and even enjoyable.
Focusing only on food
Diet is not the only factor that can influence gut symptoms. Stress, sleep, meal timing, physical activity, and gut-brain interactions also play important roles. Food is one piece of the puzzle — not the entire picture.
Why Guidance Matters During the Low FODMAP Elimination Phase
The low FODMAP diet can feel overwhelming at first because there are nuances around food combinations, serving sizes, hidden ingredients, and “FODMAP stacking.”
Many people also unintentionally stay stuck in the elimination phase because they fear symptoms returning during reintroduction.
All the clients I met who tried to do this on their own described the elimination phase as confusing and difficult to navigate without support.
This is exactly why working with a dietitian trained in the low FODMAP diet (like me) can be so helpful. Proper guidance can make the process feel far less overwhelming and help ensure you are identifying triggers accurately without unnecessary restriction.
Low FODMAP Elimination Phase: It’s A Wrap!
In summary, the FODMAP elimination phase is the first step in a structured 3-phase process designed to help you identify your IBS food triggers and improve your symptoms. The goal is not to eliminate foods forever, but to temporarily reduce high-FODMAP foods long enough to create a calmer baseline in the gut.
Most importantly, the elimination phase should be viewed as a short-term learning tool, not a permanent diet. Once symptoms improve, the next step is reintroducing foods strategically so you can build a personalized, flexible, and nourishing way of eating that supports both your gut health and your quality of life.
If you’re struggling with IBS symptoms and are ready to try the low FODMAP diet, I can help!
Take the first step by clicking on the button below and scheduling your complimentary IBS Clarity Call. We will review your symptoms and history and discuss the best next steps for you! You will come out of this call feeling relieved and hopeful that you can take control of your IBS.
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Published January 12, 2021. Updated May 11, 2026
Antonella Dewell, MS, RDN | IBS Resolution Expert
Antonella Dewell is a registered dietitian and IBS specialist based in California. She has over 2 decades of experience working in clinical research at Stanford. Since 2018, she has been running a private practice. She helps people with IBS gain real, lasting relief from IBS symptoms in just 2-4 weeks without giving up all the foods they love, so they can stop feeling anxious around food and get back to fully enjoying food and life again.
