Bloating occurs when gas builds up in the stomach or intestines, making a person feel overly full or tight inside their abdomen. And here’s the thing — gas is normal. And a normal amount of gas can cause bloating, making bloating normal, too. Even excess gas is normal at various points, making bloating even more normal.

But interestingly, people who regularly feel bloated tend not to have an abnormal, excess amount of gas, but rather an abnormally sensitive physical response to a normal amount of gas, due to hypersensitive nerve endings lining the digestive tract.

Whether this sensitivity to gas is a disorder or not is up for debate. One thing is sure: bloating isn’t always normal and can be a sign of internal disorders. Regardless, bloating is often frustrating and mystifying, leaving sufferers uncomfortable and wondering, “Why am I bloated?” What follows are the most common causes of bloating and what to do for bloating when it occurs.

Bloating and digestion

“There’s this very common assumption that, if I’m bloated, if there’s a problem in my digestive tract, then it must be something I’m eating. And that leads to these default solutions about elimination diets – okay, what should I cut?” Tamara Duker Freuman, author of The Bloated Belly Whisperer, said during a 2019 episode of the Nutrition Diva podcast. That’s not always the case, Freuman adds.

Sometimes, bloating is less about what we eat and more about how we process it. Here are the most common digestive causes of bloating, according to Freuman.

Classic indigestion

Indigestion, also known as dyspepsia, is a catch-all word for difficulty digesting, which can cause bloating in the upper abdomen, as well as other symptoms, like acidity. Indigestion has many causes — several of which are touched on below. But if your bloating is a one-off, irregular experience, it’s possible you’re simply experiencing bloating as a symptom of classic indigestion — usually as a result of eating too much or too fast, eating fatty, greasy, or spicy foods, drinking too much alcohol or caffeine, or smoking. Taking certain medications — like oral contraceptives, steroids, antibiotics, and over-the-counter pain relievers — can also cause classic indigestion and, thus, bloating.

The cure for bloating from this cause is pretty simple — eat more slowly next time, eat more healthfully, cut back on caffeine, alcohol, and/or smoking. Or consult a doctor about indigestion and bloating as a possible side effect of the medicine you’re taking.

Gastroparesis

For some people, regular bloating may indicate gastroparesis, a condition in which the normal, involuntary movement of stomach muscles, which helps to push food through the digestive tract, is impaired — thus slowing digestion and causing bloating, along with many more unpleasant symptoms such as nausea, vomiting, acidity, lack of appetite, weight loss, and more. According to the Mayo Clinic, the precise cause of gastroparesis is difficult to pin down; in some cases, it can be a complication of diabetes; for others it can be brought on by medications like antidepressants, high blood pressure medication, allergy medication, or opioid pain relievers; and for others, gastroparesis has no identifiable cause.

While it can’t be cured, the condition (and any resulting bloating) can be managed (or reduced) by dietary changes, eating smaller, more frequent meals, eating soft and thoroughly cooked foods, avoiding alcohol and fizzy drinks, drinking plenty of water, and/or exercise after a meal, according to the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.

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Irritable Bowel Syndrome

Irritable bowel syndrome, or IBS, is a disorder of the large intestines. It’s a chronic condition, with symptoms — one of which is bloating — that come and go. Other symptoms may include stomach cramps, diarrhea, constipation, and/or mucus-laced stools.

IBS has no known cause; it’s been linked to a variety of possible influences, including stress, a hypersensitive nervous system, overly slow or fast digestion, inflammation in the large intestines, and changes in gut bacteria.

When bloating is a symptom of IBS, the sensation is usually relieved once a bowel movement has occurred. However, IBS flare-ups can last days, weeks or even months, with bloating and other symptoms recurring. Over the long term, IBS and symptoms like bloating are typically managed, avoided or relieved by paying attention to triggers, which may include certain foods and stress.

Functional dyspepsia

Functional dyspepsia is indigestion that results from disordered movement by the muscles where the stomach meets the small intestines; the muscles around the end of the stomach and the duodenum, the first segment of the small intestines, essential to digestion, don’t help push food through the digestive tract like they should.

The problem is similar to gastroparesis but located in a different part of the digestive tract. And like gastroparesis, functional dyspepsia can cause bloating, as well as other symptoms such as acidity, excessive burping, nausea, and vomiting, according to the Canadian Society of Intestinal Research. And again, like gastroparesis, the condition (and its symptoms, like bloating), while it can’t be cured, typically managed by eating smaller and more frequent meals, and staying active for a couple of hours after eating.

Aerophagia

Aerophagia occurs when we gulp or swallow too much air. Consuming air via the esophagus into the digestive tract — as opposed via the trachea into the lungs — is inevitable and natural; we swallow on average 2 quarts of air a day, actually, while eating and drinking. This forms the basis for our burps and gas. But swallowing air beyond that point can cause bloating, along with possible belching, excessive flatulence, and a distended abdomen.

It can be difficult to tell whether bloating is from aerophagia or from a different form of indigestion, as the conditions share not just the full sensation, but many other similar symptoms. But indigestion is usually accompanied by nausea, vomiting, and acidity, while aerophagia is not.

Causes of aerophagia include, per Healthline: eating too quickly, talking while eating, chewing gum, drinking from a straw, drinking a lot of carbonated beverages, smoking, mouth breathing, especially at night, and strenuous exercise. People who use a CPAP machine to manage sleep apnea may also develop aerophagia.

Constipation

Constipation is a very common cause of bloating. But, according to experts, many people may not recognize constipation for what it is — and thus may not link it to their bloating.

“People think if they are having a bowel movement every day, they can’t be constipated,” Dr. Linda Lee, a gastroenterologist, tells Johns Hopkins Medicine.

They can be; constipation, she clarifies, is really defined by the following: fewer than three bowel movements per week; straining to begin or finish a bowel movement; rock-like bowel movements; and/or not feeling emptied or relieved at the end of a bowel movement.

Constipation, and any resulting bloating, has many causes, including some of the conditions explored above. But if constipation is not your normal or regular experience, one-off episodes can usually be solved by drinking more water and increasing exercise. Adding fiber to your diet can also help — which is a cure for bloating only when it’s caused by constipation. “More [fiber] is not always better” when it comes to bloating, says Tamara Duker Freuman, author of The Bloated Belly Whisperer, on the podcast. If constipation is not the cause of your bloating, or if constipation is an effect of another condition, extra fiber may only make bloating worse.

Small Intestine Bacterial Overgrowth

Small intestine bacterial overgrowth, or SIBO, is a condition characterized by too much bacteria in the small intestinal tract. The small intestines, as part of the ‘gut,’ contain good bacteria that help us break down food and absorb its nutrients during digestion. Too much bacteria can disrupt this process and, in serious cases, cause malabsorption of nutrients and deficiencies like anemia.

SIBO is a newly recognized condition, and practitioners believe is far more common than previously thought. But not much is known about it, other than the ways it manifests; SIBO can cause bloating, as well as diarrhea or constipation, nausea, fatigue, and abdominal pain, according to Johns Hopkins Medicine.

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The cause of SIBO has been linked to some of the functional problems above, as well as some medications, and chronic conditions like diabetes, but it has no clear, known cause.

Treatments for SIBO vary and require an expert’s guidance. While common wisdom might advise taking probiotics, Freuman is skeptical about whether commercial probiotic supplements will help relieve bloating from SIBO, or any other cause. “It’s not really clear that within this [bacterial] community that’s so unique, and so individual, that literally consists of tens of thousands of species and strains, that this random, one species and strain that some company was able to culture, you add that to this enormous and diverse community and it’s going to have some sort of outsized, miraculous health benefit,” she says on the podcast.

Abdomino-phrenic dyssynergia

Not all feelings of bloat make an individual appear distended — and not all distended bellies are accompanied by a bloated sensation. When bloating sensations and a swollen-looking stomach frequently occur together, however, it’s possibly a sign of abdomino-phrenic dyssyergia (APD), a functional disorder in which the diaphragm and abdominal muscles react in the opposite way they should: “With this condition, [after a meal] abdominal muscles relax when they should contract, and the diaphragm contracts when it should relax, leading to distension,” according to the International Foundation for Gastrointestinal Disorders.

The cause of APD is unknown, but it is sometimes accompanied by weak pelvic floor muscles. Like the latter, APD is typically treated through physical therapy.

Bloating and mental health

While mental health problems don’t cause bloating, many people who struggle with anxiety, depression, or simply stress often experience bloating. This could be due to any of the above digestive issues. Or, it could be due to factors unique to these struggles. For instance, antidepressant use has been linked to gastroparesis, and thus, bloating. Stress and anxiety can cause panic attacks that cause aerophagia through hyperventilation. Stress and anxiety can also cause classic indigestion — a ‘nervous stomach,’ as it’s colloquially known — and thus cause bloating. And finally, stress and anxiety have been known to exacerbate IBS symptoms — including bloating — though they don’t cause IBS directly.

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Bloating and hormones

Given the sheer number of things that can cause bloating, it’s impossible to say whether bloating is actually more common among women than men. It’s certainly more associated with women, but that could just be because certain causes of bloating are unique to women, and more regular, providing more opportunities for women to experience the sensation.

Bloating has been linked to hormonal fluctuations and is a common symptom of premenstrual syndrome (PMS) and pregnancy. Basically, the hormone progesterone, as its levels change in the course of a menstrual cycle or during pregnancy, can cause constipation, which in turn can cause a bloated feeling. Progesterone can also cause water retention, which is often mistaken for bloating.

Menstrual-related constipation, and the bloating it causes, can be managed by eating healthfully and with laxatives, in serious cases. And for water retention masquerading as bloating — drink more water. It sounds counterintuitive, but water retention occurs as a way to preserve the body’s hydration; drinking enough water ensures hydration so the body feels no need to retain water.

Bloating and diet

Food intolerance

Sometimes, bloating really is the result of what we eat, not how we digest it. Bloating can be a sign of food intolerance, for some people, along with stomach pain, flatulence, and/or diarrhea. A food intolerance can also manifest as a skin rash. These symptoms usually appear within a couple of hours of eating the food item, according to the U.K.’s National Health Service, and will repeat and possibly worsen each time that food is consumed. Dairy, wheat, and gluten products are the most common food sensitivities, according to the NHS.

There’s no single cause of food intolerances, and they’re difficult to diagnose. They’re often diagnosed through a process of elimination — by eliminating the possibility of the above and other causes of bloating, and/or by eliminating food items from your diet, then slowly adding them back in and watching for symptoms. A doctor can help guide you through this process and, if a food intolerance is diagnosed, help you manage it.