Why You’re Still Bloated: 7 Reasons It May Not Be SIBO

Bloating is one of the most common digestive complaints—and one of the easiest to oversimplify.

If you experience persistent bloating, you may have been told that the problem is “too much bacteria in the small intestine” or that you need to treat SIBO. SIBO stands for “ Small intestinal bacterial overgrowth” an infection in the small intestine that can certainly contribute to bloating. Although people often blame SIBO for bloating, it is only one possible explanation.

In fact, bloating is a remarkably nonspecific symptom. It can result from problems with digestion, intestinal transit, food fermentation in the gut, gut sensation, pelvic floor function, or even the way the diaphragm and abdominal wall respond to intestinal contents.

Research increasingly shows that bloating is not simply a measure of how much gas is present in the intestines. Two people can have similar amounts of intestinal gas and experience dramatically different levels of bloating.

If you have already treated SIBO and are still bloated—or if you’ve never had convincing evidence that SIBO is the problem—it may be time to look at the bigger picture.

Here are seven possibilities to consider.

1. Constipation or Slow Intestinal Transit

One of the most overlooked causes of bloating is simply not moving stool through the digestive tract efficiently. Constipation doesn’t always mean having only one bowel movement every several days. You can have a bowel movement every day and still have constipation if you:

• Strain to have a bowel movement
• Feel that you haven’t completely emptied
• Have hard or pellet-like stools
• Need laxatives or other aids to go
• Have prolonged periods between bowel movements
• Feel progressively more bloated as the day goes on

When stool and intestinal contents move slowly, there is more opportunity for fermentation and accumulation of gas and intestinal contents. Constipation and bloating frequently occur together, and recent reviews emphasize that chronic idiopathic constipation, IBS with constipation, pelvic floor dysfunction, and intestinal methanogen overgrowth can all contribute to this pattern. Importantly, treating constipation can improve bloating—but not everyone improves simply by increasing bowel movement frequency.

A clue that constipation may be contributing to bloating.

If your abdomen is relatively flat in the morning but becomes increasingly distended throughout the day, constipation or delayed transit deserves consideration. There are many causes for constipation, some being as simple as inadequate hydration or insufficient dietary fiber. Other causes may be physiological such as pelvic floor dysfunction.

2. You May Be Sensitive to Fermentable Carbohydrates—Without Having SIBO

Some people experience substantial bloating after eating certain carbohydrates even when they don’t have bacterial overgrowth.

FODMAPs—fermentable oligosaccharides, disaccharides, monosaccharides and polyols—are poorly absorbed carbohydrates found in plant foods and some food products that can draw water into the intestine and undergo fermentation.

Examples include:

• Onions and garlic
• Wheat in some individuals
• Beans and lentils
• Certain fruits
• Lactose-containing dairy
• Sugar alcohols such as sorbitol and mannitol

Fermentation of carbohydrates in the gut is normal. The problem may be that a person’s gut is unusually sensitive to the resulting intestinal distension. Research supports sensitivity to foods containing FODMAPs as an important contributor to bloating in susceptible individuals, particularly those with disorders of gut-brain interaction such as IBS.

This is one reason a person can feel dramatically better on a low-FODMAP diet without necessarily having treated SIBO.

However, a low-FODMAP diet should generally be viewed as a temporary diagnostic and therapeutic strategy, not necessarily a diet to follow forever. Excessive restriction can reduce dietary variety and may have negative nutritional and microbiome consequences since these FODMAPs also act as prebiotics in the gut.

3. Your Gut May Be Hypersensitive to Normal Amounts of Gas

This is one of the most important, and least understood, concepts in chronic bloating: You don’t necessarily have to produce more gas to feel more bloated.

Some people have visceral hypersensitivity, meaning the nervous system is more sensitive to normal stretching or distension of the gastrointestinal tract. Think of it like turning up the volume on a speaker. A normal amount of intestinal stretching might barely register for one person but feel intensely uncomfortable to another.

Visceral hypersensitivity is well documented in a subset of patients with IBS and can contribute to bloating, abdominal discomfort and pain. Visceral hypersensitivity can result from disorders of gut-brain interaction, including irritable bowel syndrome, functional dyspepsia, and functional abdominal bloating. It may also coexist with constipation, food intolerance, altered motility, or previous gastrointestinal illness such as a viral infection or intestinal infection acquired from food poisoning. This is often called post-infectious IBS.

This helps explain why repeatedly trying to “kill the bacteria” may not solve the problem.If the underlying problem is altered gut sensation, reducing bacteria may have limited impact.

The treatment strategy may instead involve:

• Improving bowel regularity
• Identifying dietary triggers
• Gradually expanding food tolerance
• Addressing stress and sleep
• Brain-gut behavioral therapies
• Selected neuromodulating medications when appropriate

The goal is not simply to eliminate every source of fermentation. It is to help the gastrointestinal nervous system respond more normally to what is happening inside the gut.

4. The Problem May Be How Your Diaphragm and Abdominal Wall Respond

This is one of the most fascinating explanations for visible abdominal distension.

A condition called abdominophrenic dyssynergia can cause the diaphragm to contract downward while the abdominal wall relaxes in response to intestinal contents.

This causes the abdomen to visibly protrude without a dramatic increase in the amount of gas inside the intestine.

In other words, some abdominal distension is not simply “something expanding inside your abdomen.” It can be a motor response of the abdominal muscles and diaphragm. This phenomenon has been increasingly recognized in patients with chronic functional bloating and distension. This is also why diaphragmatic breathing, behavioral therapies and specialized biofeedback approaches may help selected patients.

5. Pelvic Floor Dysfunction Can Cause Bloating

If you have difficulty emptying your bowels, don’t overlook the pelvic floor. Normally, the pelvic floor muscles relax when you need to have a bowel movement. With Dyssynergic defecation, these muscles may fail to relax appropriately or may even contract or tighten during attempted evacuation.

This can result in:

• Straining
• Incomplete evacuation
• A sensation of blockage
• Multiple attempts to have a bowel movement
• Constipation
• Bloating and abdominal distension

Research has found a strong association between symptoms of pelvic floor dysfunction and abdominal bloating/distension.

The American Gastroenterological Association recommends considering anorectal physiology testing when bloating and difficult evacuation suggest a pelvic floor disorder. If dyssynergia is identified, pelvic floor biofeedback can be an effective treatment.

This is an important example of why simply adding more fiber to your diet or repeatedly treating presumed SIBO may not address the actual problem.

6. Your Stomach May Not Be Emptying Normally

Bloating does not always come from the intestines. Sometimes the problem starts higher up in the digestive tract.

Delayed gastric emptying (gastroparesis) can cause:

• Early fullness
• Feeling full for hours after eating
• Nausea
• Upper abdominal bloating
• Abdominal discomfort
• Vomiting in more severe cases

Gastroparesis can occur with diabetes, after certain surgeries, with some medications, or without an identifiable cause. A particularly useful clue is eating a meal and feeling stomach fullness and discomfort for hours. This is a different pattern compared to someone who feels lower abdominal distension several hours after eating fermentable carbohydrates. The distinction matters because the treatment approach is completely different.

7. The Gut-Brain Connection May Be Driving Your Symptoms

This does not mean your symptoms are “all in your head.”

The gastrointestinal tract has an extensive nervous system that communicates continuously with the brain.

Changes in gut sensation, motility, autonomic signaling, stress physiology and the brain’s interpretation of intestinal signals can all influence how bloating is experienced.

This is particularly relevant to disorders such as:

• Irritable bowel syndrome
• Functional dyspepsia
• Functional abdominal bloating
• Functional abdominal distension

These conditions are now generally understood as disorders of gut-brain axis, rather than simply disorders caused by abnormal bacteria.

The relationship between the gut and the brain is bidirectional: gastrointestinal signals influence the brain, while the brain and autonomic nervous system influence intestinal motility, sensation and abdominal muscle activity. The gut and the brain are always in communication.

For some patients, treatment approaches such as cognitive behavioral therapy, gut-directed hypnotherapy, diaphragmatic breathing, vagal nerve stimulators and other carefully selected neuromodulators can be surprisingly effective.

Can SIBO be the Cause of Your Gut Symptoms?

SIBO can contribute to bloating, gas, abdominal discomfort and altered bowel habits. But bloating by itself does not prove SIBO. There are many other causes of abdominal bloating.For one person, it may be bacterial overgrowth, for another, it may be constipation. Other factors, such as FODMAP sensitivity or impaired gastric emptying may be affecting gut function. In many patients, several mechanisms can coexist.

Evaluating the Root Cause of Bloating

Instead of immediately asking, “How do I get rid of the bacteria?”, start by asking: What does the bloating look like? Some common patterns linked to bloating are listed below.

Symptom and Food Pattern Awareness is Important

People often live with GI symptoms but never pay attention to when symptoms happen and any dietary patterns associated with symptoms. Keeping a food and symptom journal can elucidate connections between certain foods and symptoms. You can also monitor how mood is related to gut symptoms. Anxiety and chronic stress can impact gut symptoms so noting mood changes can be helpful when determining the root cause of bloating or other gut issues.

Persistent bloating deserves a broader evaluation that considers motility, constipation, pelvic floor function, food intolerance, visceral sensitivity, gastric emptying and the gut-brain connection. The most effective treatment is often not another round of antimicrobial supplements or medication but rather looking at the big picture including past medical history, life stressors, food intolerances, and lifestyle. Working with a knowledgeable healthcare professional can help you find the right tests to evaluate why you are experiencing bloating or other digestive problems. Once you determine what is driving the symptoms, finding an effective treatment along with lifestyle modifications can help heal your gut and improve quality of life.

Selected References

1. Mari A, et al. Bloating and Abdominal Distension: Clinical Approach and Management. Adv Ther. 2019. PMID: 30879252.
2. Moshiree B, et al. AGA Clinical Practice Update on Evaluation and Management of Belching, Abdominal Bloating, and Distention: Expert Review. Gastroenterology. 2023. PMID: 37452811.
3. Cangemi DJ, Lacy BE. A Practical Approach to the Diagnosis and Treatment of Abdominal Bloating and Distension. Gastroenterol Hepatol (N Y). 2022. PMID: 35505814.
4. Tuck CJ, et al. Food Intolerances. Nutrients. 2019. PMID: 31336652.
5. Damianos JA, et al. Abdominophrenic Dyssynergia: A Narrative Review. Am J Gastroenterol. 2023. PMID: 36191283.
6. Agrawal A, Whorwell PJ. Review article: abdominal bloating and distension in functional gastrointestinal disorders—epidemiology and exploration of possible mechanisms. Aliment Pharmacol Ther. 2008. PMID: 17931344.
7. Wilkinson JM, et al. Gas, Bloating, and Belching: Approach to Evaluation and Management. Am Fam Physician. 2019. PMID: 30811160.
8. Cangemi DJ, et al. Constipation with bloating: a clinical approach to evaluation and management. Ann Med. 2026. PMID: 42319080.