Painting of man with IBS eating a low-FODMAP bulking diet.

The Low-FODMAP Bulking Diet (for Gaining Weight)

FODMAPs are the enigmatic compounds that lurk within certain carbohydrates. They aren’t good or bad. It all depends on how you respond to them. Most people digest them without any issue, but they can wreak havoc on some people with more irritable bowels (IBS).

Here’s the problem. People with more sensitive digestive systems often eat less food, causing them to lose weight and preventing them from building muscle. I was one of these unfortunate skinny guys, underweight and unable to eat enough food to bulk up.

So, we need to eat more food, but how? Whenever we try, our guts flare up, causing bloating, pain, constipation or diarrhea. That’s where a low-FODMAP diet comes in. It isn’t a cure-all, but it often helps. It’s often worth trying.


If you’re struggling with serious digestive issues, it’s often helpful to work with a dietician in person. Cassandra is a registered nutritionist, but our expertise is helping people bulk up, build muscle, and gain weight, not resolving chronic digestive issues.

What Are FODMAPs?

FODMAP stands for “Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols.” These carbohydrates are harder to break down, allowing them to fight their way into our large intestines unaltered. There, our gut bacteria feast on them, producing gas as a byproduct. This causes the gut to hoard water, leading to bloating, pain, and diarrhea.

Here are some of the more common FODMAPs:

  1. Oligosaccharides: Fructans and galacto-oligosaccharides (GOS) are found in wheat, barley, rye, onion, garlic, and legumes.
  2. Disaccharides: Lactose, the milk sugar, dwells in dairy products like milk, cheese, and yogurt.
  3. Monosaccharides: Fructose, the fruit sugar, hiding in apples, pears, honey, and high fructose corn syrup.
  4. Polyols: Sorbitol and mannitol lurk in sugar alcohols and fruits like avocados, cherries, and peaches.

If you’re struggling with digestive issues, temporarily banishing these FODMAPs from your diet may give your gut some respite. You don’t need to avoid all of them, and you don’t need to avoid them forever. The idea is to try removing them, see if it solves the problem, and then try adding them gradually back in, keeping track of what symptoms you experience.

How to Eat a Low-FODMAP Bulking Diet

If FODMAPs are aggravating your gut, we can build your bulking diet on a foundation of low-FODMAP foods. These foods tend to be more comfortable to eat in larger quantities, making it easier to get into a calorie surplus, allowing you to gain weight and build muscle.

  1. Proteins: Fish, eggs, meat, pumpkin seeds, peanuts, and lactose-free milk.
  2. Carbs: rice, quinoa, potatoes, oats, grapes, oranges, strawberries, blueberries, pineapple, bananas (not overripe), kiwis, and eggplant.
  3. Healthy fats: Olive oil (for drizzling on veggies) and avocado oil (for cooking). You can also have small servings of nuts and seeds, such as almonds, macadamia nuts, peanuts, pumpkin seeds, and sunflower seeds. Some cheeses are low in FODMAPS, too: Brie, Camembert, cheddar, and feta.
  4. Fibre: carrots, tomatoes, bell peppers, green beans, cucumbers, zucchini, and spinach.
  5. Herbs and spices: Most herbs and spices are low in FODMAPs. Onion and garlic powder can sometimes cause issues. You can test them when you begin reintroducing foods.
  6. Beverages: water, tea, and coffee (without sweeteners or milk).

These foods are unlikely to cause issues. That means you can start your day with a smoothie or some oatmeal made with blueberries and lactose-free milk. For lunch, maybe you have a serving of trail mix, some cheese, and a banana. For dinner, maybe you make a one-pan dish with salmon, chopped potatoes, and green beans tossed in olive oil and spices.

You can eat other foods, too. Just be more careful with them, at least until you know how they affect you. Let’s cover how to do that.

Adding FODMAPS Back In

The low FODMAP diet is an elimination diet divided into three stages.

  1. The Elimination Phase: stop eating high-FODMAP foods for 5 weeks. If your symptoms improve, it hints that FODMAPs may have been the problem. This is valuable information.
  2. The Reintroduction Phase: every 3 days, introduce a new FODMAP food into your diet. Eat a reasonable amount of that food. One serving, not seventeen.
  3. The Joyful Bulking Phase: Keep eating the foods that agree with you. Eat the most plentiful, balanced, varied diet your gut can manage. As your gut becomes more robust, you may gain the ability to digest a wider variety of foods.
Shane Duquette

Shane has over 10 years of full-time experience helping over 10,000 skinny guys build muscle by lifting weights, eating a good bulking diet, and living a healthy lifestyle. He's the founder of Bony to Beastly, Bony to Bombshell, and Outlift.

Cassandra Duquette

Cassandra is a registered nutritionist living in Cancun, Mexico. She believes vitality comes from an abundant diet, regular exercise, and a healthy lifestyle. Her specialty is nutrition. She's gained 20 pounds.

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