Keto and low FODMAP are not the same diet, and following one does not automatically mean you’re following the other. They restrict different things: keto limits total carbohydrates (typically to under 20-50 grams per day), while low FODMAP limits specific types of fermentable carbohydrates that cause digestive symptoms. There’s significant overlap between the two, but several popular keto foods are high in FODMAPs, and some low FODMAP foods are too high in carbs for keto.
What Each Diet Actually Restricts
Keto’s single rule is keeping carbohydrates low enough to shift your body into burning fat for fuel. It doesn’t distinguish between types of carbs. A gram of sugar and a gram of fructan are treated the same.
Low FODMAP targets a specific group of short-chain fermentable carbohydrates: lactose, excess fructose, fructans, galactans, and sugar alcohols like sorbitol, mannitol, and xylitol. These carbs are poorly absorbed in the small intestine and get fermented by gut bacteria, producing gas, bloating, and diarrhea in sensitive people. The diet was developed primarily for irritable bowel syndrome and doesn’t restrict fat or protein at all.
Because keto cuts carbs so drastically, it naturally eliminates many high FODMAP foods. You won’t be eating wheat products, legumes, most fruits, or honey on keto, and those are some of the biggest FODMAP sources. But the overlap isn’t complete.
Keto Foods That Are High in FODMAPs
This is where the two diets diverge, and it catches people off guard. Several staples of a standard keto meal plan will trigger symptoms if you’re FODMAP-sensitive.
- Garlic and onions. These are the backbone of keto cooking for flavor, and both are among the highest FODMAP foods. Fructans are the culprit. Even small amounts can cause problems.
- Cauliflower. The go-to keto substitute for rice, pizza crust, and mashed potatoes is high in FODMAPs, particularly polyols.
- Mushrooms. A common keto side dish, but high in polyols like mannitol.
- Avocado. Low carb and high fat, so it’s a keto favorite. In larger servings (more than about one-eighth of a whole avocado), it becomes high in sorbitol.
- Asparagus, Brussels sprouts, and broccoli. All popular on keto plates, all high FODMAP in typical serving sizes.
- Cashews and pistachios. Keto-friendly by carb count, but high in FODMAPs. Almonds in larger portions are problematic too.
- Cream cheese and soft cheeses. These retain more lactose than hard, aged varieties, which can be an issue depending on your sensitivity.
If you’re eating keto and still dealing with bloating, cramping, or irregular bowel habits, one or more of these foods could be the reason.
Foods That Work for Both Diets
The good news is that a large category of foods fits comfortably in both plans. Meat, poultry, and fish are naturally free of FODMAPs and contain zero carbs. Eggs, butter, and most cooking oils work perfectly for both. Hard, aged cheeses like cheddar, Parmesan, and Swiss are very low in lactose and fit both diets easily. Goat milk cheeses tend to be even lower in lactose and easier to digest.
For vegetables, you have solid options: zucchini, eggplant, green beans, bok choy, green bell peppers, cucumber, lettuce, and spinach are all low FODMAP and low carb. Carrots and tomatoes work in moderate portions. For nuts, macadamias, pecans, walnuts, and pine nuts are safe choices on both diets.
Herbs like basil, chives (as a mild onion substitute), rosemary, and thyme add flavor without FODMAPs. Garlic-infused oil is a widely used workaround: the fructans in garlic don’t dissolve in fat, so the oil carries the flavor without the FODMAPs.
Sweeteners Need Careful Attention
Keto dieters rely heavily on sugar substitutes, and this is a minefield for FODMAP sensitivity. Several common sugar alcohols are themselves FODMAPs.
Xylitol, sorbitol, mannitol, maltitol, and isomalt are all classified as polyols, one of the core FODMAP groups. These show up in sugar-free gums, protein bars, keto baked goods, and many “keto-friendly” packaged products. If you’re combining both diets, check ingredient labels carefully.
Stevia and monk fruit extract are safe on both counts: they contain no carbs and no FODMAPs. Erythritol is generally better tolerated than other sugar alcohols because most of it gets absorbed in the small intestine before reaching the colon, though very large amounts can still cause digestive discomfort in some people. These three sweeteners are your best options when combining the diets.
Why a Very Low Carb Diet May Help IBS on Its Own
There’s an interesting wrinkle here. Even without specifically targeting FODMAPs, cutting carbs dramatically can reduce IBS symptoms, likely because you’re unintentionally cutting out many fermentable carbs at the same time.
A study published in Clinical Gastroenterology and Hepatology tested a very low carbohydrate diet (4% of calories from carbs, roughly equivalent to keto) in people with diarrhea-predominant IBS. All 13 participants who completed the four-week trial reported adequate symptom relief, and 77% reported relief for every single week. Bowel movements dropped from an average of 2.6 per day to 1.4. Stool consistency shifted from diarrheal to normal. Abdominal pain scores fell by more than half. These improvements were independent of weight loss.
This suggests that for some people with IBS, keto alone may provide substantial relief. But if you’re on keto and still having gut issues, the remaining symptoms likely point to specific high FODMAP foods that survived your carb cuts, like garlic, onions, cauliflower, or sugar alcohols in keto products.
How to Combine Both Diets Practically
If you want to follow both keto and low FODMAP simultaneously, the core strategy is straightforward: build your meals around protein and fat sources that are naturally FODMAP-free, then add low FODMAP vegetables for fiber and nutrients.
A typical day might look like eggs cooked in butter with spinach and green bell pepper for breakfast, a salad with grilled chicken, olive oil, cucumber, and walnuts for lunch, and salmon with zucchini sautéed in garlic-infused oil for dinner. Snacks could include hard cheese, macadamia nuts, or olives.
The biggest practical challenge is flavor. Losing garlic and onions means rethinking how you season everything. Garlic-infused oil, the green tops of spring onions (which are low FODMAP, unlike the white bulb), chives, ginger, lemon juice, and mustard all help fill the gap.
The other challenge is variety. Both diets are already restrictive on their own, and combining them narrows your vegetable and nut options further. Pay attention to getting enough fiber from the vegetables you can eat, since both diets tend to run low on it. Chia seeds and flaxseeds are low FODMAP, very low in net carbs, and good sources of fiber that fit both plans.
The FODMAP Reintroduction Phase Still Matters
Low FODMAP is designed to be temporary. The elimination phase typically lasts two to six weeks, followed by a structured reintroduction where you test one FODMAP group at a time to identify your personal triggers. Most people with IBS find they react to one or two FODMAP categories, not all of them.
If you’re combining both diets, don’t skip this step. You might discover that you tolerate lactose just fine but react to fructans, which means you can add back cream-based sauces but still need to avoid garlic and onions. Or you might handle small amounts of cauliflower without issues. The goal is to end up with the least restrictive version of your diet that still controls symptoms, which becomes especially important when you’re already limiting carbs.