Cutting carbohydrates is often thought to be a straight-forward method for losing weight quickly, but it doesn't come without repercussions.
One very common side effect of cutting out carbs is gastrointestinal discomfort — particularly in the form of gas and bloat. If you're experiencing these uncomfortable stomach issues, you may want to explore the reasons why and what you can do to calm them.
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What Is Low-Carb, Anyway?
Low-carb diets come in many varieties and may call for limiting daily carb intake to below 100 grams, 50 grams, 30 grams or even 20 grams. The popular ketogenic diet is on the lower end of that scale. On a keto diet, which is a high-fat, moderate-protein diet, you might be getting as few as 5 to 10 percent of your calories from carbohydrates, according to December 2020 report in StatPearls.
Why You're Gassy and Bloated on Keto or Another Low-Carb Diet
1. You're Missing Out on Fiber
This is probably the most common reason for experiencing gastrointestinal woes on a low-carb diet. Newbies often struggle to maintain proper amounts of fiber in their diets when they first start out, which can lead to discomfort. ICYMI, fiber is a type of carb.
"Fruits, vegetables and whole grains are excellent sources of dietary fiber, which keeps our digestive systems in tip-top shape. Avoiding these foods can result in decreased transit time (the amount of time it takes food to travel through our digestive tracts) and may lead to increased gas and bloating," Christie Gagnon, RD, tells LIVESTRONG.com.
People should aim to get 14 grams of fiber for every 1,000 calories consumed per day, per the Academy of Nutrition and Dietetics. Most Americans fail to get anywhere close to these recommendations, but reaching these numbers can be especially hard when you're not eating carbs.
Fiber is found only in plant foods such as fruits, vegetables, whole grains and beans. Because your body doesn't digest or absorb fiber, it moves throughout the digestive system relatively unchanged, adding bulk to stool and assisting the body to empty its bowels more easily and frequently.
Those plant foods also serve a purpose for good gut health. "Low-carb diets can lack fiber, whole grains and prebiotics, which serve as a fuel source for the healthy gut bugs in your intestines," says Lacey Dunn, RD. "With lack of fiber fuel plus excessive protein intake, this can leave you with gas, abdominal pain and uncomfortable bloat."
You don't have to — nor should you — avoid plant-based foods on your low-carb diet. These foods are crucial to incorporate into your everyday diet, you'll just need to plan ahead and pay attention to your fiber intake.
Non-starchy vegetables, such as spinach, broccoli and cauliflower are nutrient-rich, low in carbs and high in fiber. Certain fruits, such as berries, are also high in fiber and can be included in a low-carb diet.
When you take into account the net carb value — carbs minus fiber — these plant foods can fit perfectly within your daily carb budget:
- 1 cup raspberries: 8 grams fiber, 6.7 grams net carbs
- 1 cup blackberries: 7.6 grams fiber, 6.2 grams net carbs
- 1/2 avocado: 6.7 grams fiber, 1.8 grams net carbs
- 1 cup raw broccoli: 2.4 grams fiber, 3.6 grams net carbs
- 1 cup raw cauliflower: 2.1 grams fiber, 3.2 grams net carbs
- 3 cups raw spinach: 2 grams fiber, 1.2 grams net carbs
2. You're Eating Too Many Sugar Alcohols
Sugar alcohols are often used to replace real sugar in sweet foods that are low in carbohydrates. Unlike real sugar, sugar alcohols aren't fully absorbed by the body, leading many dieters to eat them without being mindful of moderation.
Some common sugar alcohols include xylitol, sorbitol, and erythritol. If you see an "-ol" on the end of an ingredient, odds are it's a sugar alcohol.
Even though sugar alcohols are often seen as "better for you" because they don't raise your blood sugar quite as high as sugar, they are linked with irritable bowel syndrome (IBS) and flatulence, according to October 2016 research in the International Journal of Dentistry. And if being extra gassy isn't bad enough, taking in large amounts of sugar alcohols can cause diarrhea.
"If you're replacing regular sugar with sugar alcohols in order to better align with a low-carb diet, you may be setting yourself up for unwanted gastrointestinal distress," says Jamie Lee McIntyre, RDN. "Sugar alcohols, like sorbitol and mannitol, can cause diarrhea, gas and cramping. In fact, any food that contains sorbitol or mannitol must include a warning on their label that excess consumption may have a laxative effect."
Be mindful of those sugar alcohols. If you're swapping out old favorites for food products that boast "low-carb" on their labels, you may want to cut out the packaged stuff and focus on incorporating more whole foods into your diet.
Read food labels: If a new-to-you ingredient ends in "-ol," there's a good chance it's a sugar alcohol.
3. You're Dehydrated
If you're just starting with a low-carb diet, some of your GI issues may be caused by the diet itself.
A low-carb, high-fat diet may initially have a diuretic effect on your body. This is the reason you may initially lose weight on a ketogenic diet, according to the StatPearls report. All that water loss can leave you dehydrated, which, in turn, can leave you feeling bloated and constipated.
Drinking more water is one obvious but important way to combat these issues. You might feel odd adding more fluid to your already-bloated belly, but doing so will help your system relieve some of the distention.
The Bottom Line
If you're starting a new, low-carb diet, it's possible that you'll experience some uncomfortable side effects including gas and bloat.
Adding in more fiber to your diet will likely improve your digestive issues, but you'll need to be thoughtful about your approach. If your current fiber intake is extremely low, up your fiber slowly, and be sure to increase the amount of water you drink as you do so.
Without upping both water and fiber intake, you might just end up right back where you started: bloated and gassy.
- National Center for Biotechnology Information: "Ketogenic Diet"
- International Journal of Dentistry: "Gastrointestinal Disturbances Associated with the Consumption of Sugar Alcohols with Special Consideration of Xylitol: Scientific Review and Instructions for Dentists and Other Health-Care Professionals"
- Northwestern Medicine: "How to Beat the Bloat"
- Academy of Nutrition and Dietetics: "Fiber"
- Christie Gagnon, RD