Can IBS cause floating stools? Have you noticed your poo floating in the toilet and wondered if it could be a sign of IBS—or something more serious?

You’re not alone. Changes in bowel habits are one of the most common reasons people search for health information online, and floating stools often cause unnecessary worry. Many people immediately fear they have a problem digesting fat or even a serious disease affecting the pancreas. In reality, the explanation is usually much simpler.

Most floating stools are caused by excess gas trapped within the stool, making it less dense than water. This often happens after eating foods that are fermented by your gut bacteria and is particularly common in people with irritable bowel syndrome (IBS), who frequently experience bloating and excess wind.

However, floating stools are not always caused by gas. If they are persistently pale, greasy, oily or difficult to flush, they may indicate that fat is not being absorbed properly. This can occur in conditions such as coeliac disease, exocrine pancreatic insufficiency or disorders affecting bile production. These symptoms should always be assessed by a healthcare professional rather than assumed to be IBS.

Quick answer: Can IBS cause floating stools?

Yes, IBS can contribute to floating stools, but it is not the only possible cause.

People with IBS often experience bloating, excess wind and changes in bowel habits. These symptoms are largely driven by changes in the way the gut moves and processes food rather than by structural damage to the intestines. As carbohydrates are fermented by bacteria in the large bowel, gas is produced. Some of this gas can become trapped within the stool, making it float.

Importantly, floating stools are not one of the symptoms used to diagnose IBS, and they do not necessarily mean you have the condition. Likewise, they do not automatically indicate fat malabsorption.

If your stools are occasionally brown, formed and easy to flush, excess gas is the most likely explanation.

However, if they become persistently greasy, oily, pale, bulky or difficult to flush—especially if accompanied by diarrhoea, unexplained weight loss or nutritional deficiencies—you should speak to your GP, as these features may suggest an underlying condition that requires investigation.

What does the research say about floating stools?

Research suggests that stools usually float because they contain more gas or water, which reduces their density, rather than because they contain excess fat. A human study published in the New England Journal of Medicine found that differences in stool buoyancy were mainly related to gas content and concluded that a floating stool should not, on its own, be considered evidence of fat malabsorption.

More recent research has explored the role of the gut microbiome. In a 2022 mouse study, stools from germ-free mice sank, whereas colonisation with intestinal microorganisms increased the likelihood of flotation. This supports the idea that gases and other changes produced by gut bacteria can influence stool density. However, because this was an animal study, it cannot tell us exactly which bacteria cause floating stools in humans.

The practical message is that an occasional brown floating stool is usually related to trapped gas and may be completely normal. Fat malabsorption becomes more concerning when stools are also persistently pale, oily, greasy, bulky, particularly foul-smelling or difficult to flush.

Why do stools float?

The most common reason stools float is because they contain more gas than usual.

A stool floats when it is less dense than water. This happens because tiny pockets of gas become trapped within it during digestion. Gas is produced naturally as the trillions of bacteria living in your large intestine break down carbohydrates that haven’t been fully digested in the small intestine. This process, known as fermentation, is completely normal and plays an important role in maintaining a healthy gut microbiome.

Foods such as beans, lentils, onions, garlic, apples and wholegrains are particularly rich in fermentable carbohydrates. These foods are highly nutritious, but in some people, especially those with IBSthey can lead to increased gas production, bloating and occasionally floating stools.

Less commonly, stools float because they contain an unusually high amount of undigested fat. Fat is less dense than water, so stools containing excess fat are more likely to float. Unlike gas-related floating stools, they are usually pale, greasy, bulky, foul-smelling and difficult to flush. This is known as steatorrhoea and is a sign that fat digestion or absorption may be impaired.

Understanding this distinction is important because floating stools alone cannot tell you what is causing them. Looking at their colour, consistency, whether they appear greasy and whether you have other symptoms provides much more useful information than whether they float.

Increased fermentation and gas production

One of the main reasons stools float in IBS is because of intestinal fermentation.

Not all carbohydrates are completely digested and absorbed in the small intestine. Some continue into the large intestine, where they are broken down by the trillions of bacteria that naturally live in your gut. As these bacteria ferment carbohydrates, they produce gases such as hydrogen, methane and carbon dioxide.

This process is completely normal and happens in everyone.

However, many people with IBS are more sensitive to these normal digestive processes. After eating foods rich in fermentable carbohydrates—often called FODMAPs—they may experience symptoms including:

• bloating
• abdominal discomfort
• excessive wind
• rumbling noises
• abdominal distension

Some of this gas can become trapped within the stool, making it less dense than water and causing it to float.







Why aren’t all carbohydrates absorbed?

Normally, most carbohydrates are broken down by digestive enzymes in the small intestine into simple sugars that can be absorbed into your bloodstream. However, some carbohydrates escape digestion because:

• They are naturally poorly absorbed, such as lactose in people with lactose intolerance or fructose intolerance.
  
• They are fermentable fibres (such as fructans, galacto-oligosaccharides and resistant starch), which humans cannot digest but beneficial gut bacteria can.
  
• Food moves through the gut too quickly for complete digestion.
  
• In SIBO, bacteria in the small intestine ferment carbohydrates before your body has had a chance to absorb them, leading to earlier and often greater gas production.
  

This is why reducing certain FODMAP carbohydrates can temporarily improve symptoms in some people with IBS—they reduce the amount of fermentable carbohydrate available for bacteria, which in turn reduces gas production.

Gut transit also plays a role

The speed at which food moves through your digestive tract can also influence whether stools float.

If you have IBS with diarrhoea (IBS-D), food often passes through the bowel more quickly than usual. Faster transit leaves less time for water to be absorbed, producing looser stools that may trap more gas.

If you have IBS with constipation (IBS-C), the opposite can happen. Stool remains in the colon for longer, giving gut bacteria more time to ferment carbohydrates. This prolonged fermentation may increase gas production, contributing to bloating, trapped wind and, occasionally, floating stools.

People with mixed IBS (IBS-M) may experience both of these patterns at different times, which may explain why floating stools are sometimes reported during both constipation and diarrhoea flare-ups.

The role of FODMAPs

Many of the foods that trigger IBS symptoms are rich in FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols). These carbohydrates are poorly absorbed in some people and are rapidly fermented by bacteria in the large intestine.

Examples include:

• onions
• garlic
• wheat
• beans and lentils
• apples and pears
• milk in people with lactose intolerance
• sugar-free sweets containing polyols

The extra fermentation can increase gas production, making floating stools more likely alongside bloating and excess wind.

It’s important to remember that these are healthy foods. They don’t cause IBS, and they don’t need to be avoided forever. A low FODMAP diet is intended as a short-term elimination diet followed by a structured reintroduction phase to identify your individual triggers.

What does the research say?

Research specifically looking at floating stools is surprisingly limited, but one observational study found that floating stools were reported more frequently in people with functional bowel disorders, including IBS, than in people with other gastrointestinal conditions.

The researchers suggested that increased gas within the stool, rather than fat malabsorption, was the most likely explanation. However, this was an observational study, so it shows an association rather than proving that IBS directly causes floating stools.

Taken together, the available evidence suggests that occasional floating stools in people with IBS are most often related to increased intestinal gas and altered gut function rather than a serious underlying disease.

Is your stool floating because of gas or fat?

Floating alone cannot reliably distinguish excess gas from fat malabsorption. You need to consider the overall appearance of the stool and your other symptoms.

Fatty stools are known medically as steatorrhoea.

They are often:

• pale
• bulky
• greasy
• oily
• sticky
• unusually foul-smelling
• difficult to flush

If your stools regularly have these features, you should discuss them with your doctor.

What are the possible causes of floating stools?

What tests should you consider?

If your stools are persistently floating, particularly if they are also pale, greasy, broken up or accompanied by nausea, diarrhoea, weight loss or abdominal pain, it’s worth speaking to your GP. The first step is usually to rule out other digestive conditions that can cause similar symptoms.

Your doctor may recommend blood tests to check for coeliac disease, vitamin deficiencies, liver problems and inflammation. They may also request stool tests, such as faecal calprotectin to look for inflammatory bowel disease and faecal elastase to assess whether your pancreas is producing enough digestive enzymes. Depending on your symptoms, further investigations such as an abdominal ultrasound (to assess the liver and gallbladder) or, less commonly, an endoscopy or colonoscopy may also be considered.

If these investigations are normal but you continue to experience symptoms such as persistent bloating, excessive wind, frequent morning bowel movements, nausea and floating stools, a SIBO breath test may be a useful next step.

SIBO (small intestinal bacterial overgrowth) can cause excess fermentation within the small intestine, leading to increased gas production, bloating and floating stools. In some people, SIBO may also interfere with normal digestion, resulting in loose or broken-up stools and the sensation that food is not being fully digested.

Research suggests that approximately one in three people with IBS may also test positive for small intestinal bacterial overgrowth, or SIBO. SIBO appears to be more common in people with diarrhoea-predominant IBS, while methane or intestinal methanogen overgrowth is more strongly associated with constipation.

SIBO can develop when the normal mechanisms that clear bacteria from your small intestine are disrupted, for example after food poisoning, reduced gut motility, abdominal surgery, low stomach acid or certain medical conditions. In many people, more than one factor is involved, and stress may worsen symptoms without being the primary cause.

What diet should you follow if your stool floats?

There isn’t a single diet that’s right for everyone with floating stools. The most appropriate approach depends on the underlying cause.

If your floating stools are accompanied by bloating, excessive wind and IBS-like symptoms, reducing highly fermentable foods (FODMAPs) for a short period under the guidance of a healthcare professional may help reduce gas production and improve symptoms. If you would like help with this diet we offer consultations and will be able to guide you through the best foods to eat and avoid.

Key takeaway:

Floating stools are most commonly caused by excess gas from fermentation, particularly in people with IBS or SIBO. However, persistent pale, greasy or oily stools may indicate fat malabsorption and should be investigated. A good diet to try short-term is a 4 week die that will reduce highly fermentable foods (FODMAPs).

Still concerned about your floating stools?

If your bowel symptoms are affecting your quality of life, it is important not to simply assume that they are caused by IBS.

At our sister clinic, IBS and Gut Disorder Clinic we can review your symptoms, diet, medical history and previous investigations in detail. Where appropriate, we can also discuss whether further testing may help identify factors such as SIBO, food intolerances or gut dysbiosis.

We will then put together a clear, tailored plan to help you feel more comfortable and in control of your digestive health.

You can book a consultation through ibs-solutions.co.uk.

If you would prefer to begin with testing, you can also order a SIBO breath test.

FAQs

Can IBS cause floating stools?

IBS may contribute to floating stools indirectly.

IBS can affect the speed at which food and waste move through your digestive tract. It may also alter how sensitive your bowel is to gas and how effectively gas moves through the intestine.

If certain carbohydrates are not completely absorbed in your small intestine, they pass into the large intestine, where bacteria ferment them. This can increase gas production.

Some of this gas may become incorporated into the stool, making it float.

IBS does not normally cause significant fat malabsorption. Therefore, persistently greasy, oily or pale stools should not automatically be attributed to IBS.

Why do you need to go to the toilet several times in the morning?

Your bowel naturally becomes more active after waking and eating. This is partly due to the gastrocolic reflex, a normal response that stimulates movement in the colon after food enters the stomach.

In people with IBS, this reflex may be more pronounced.

You may therefore:

• open your bowels several times in the morning
• pass a small amount on each occasion
• experience urgency after breakfast or coffee
• notice that your stool becomes progressively looser
• feel that your bowel has not emptied completely

This pattern is commonly associated with IBS, but it may also occur with bile acid diarrhoea, coeliac disease, SIBO, infection and other digestive conditions.

Why does your stool look broken up?

Loose stools that fall apart easily or have fluffy, ragged edges are often linked to increased water content or faster movement through the bowel.

They may occur because:

• food is moving through your intestine more quickly
• you have mild diarrhoea
• your stool contains more water
• increased gas has affected the stool’s structure
• you have recently increased your fibre intake
• you have eaten foods that are poorly tolerated

Occasional broken-up stools are not necessarily concerning. However, consistently loose stools accompanied by weight loss, bleeding, persistent pain or nutritional deficiencies should be investigated.

Why can you see undigested food?

Seeing recognisable pieces of food does not always mean that your body is failing to digest nutrients properly.

Certain plant foods contain fibrous outer layers that human digestive enzymes cannot fully break down. These may remain visible in your stool.

Common examples include:

• sweetcorn
• peas
• tomato skins
• pepper skins
• mushrooms
• seeds
• leafy vegetables
• beans

You may also notice more visible food if you eat quickly, do not chew thoroughly or if food is moving rapidly through your digestive system.

However, regularly seeing large amounts of food alongside chronic diarrhoea, greasy stools, weight loss or nutritional deficiencies may require further investigation.

Can SIBO cause floating stools?

SIBO, or small intestinal bacterial overgrowth, could contribute to floating stools, particularly if you also experience bloating, excessive wind, nausea or altered bowel habits.

In healthy digestion, most bacterial fermentation takes place in the large intestine. In SIBO, excessive numbers of bacteria are present in the small intestine, where they may ferment carbohydrates before those carbohydrates have been fully absorbed.

This can produce additional gas earlier in the digestive tract.

In more severe or long-standing cases, some bacteria may alter bile acids before they have completed their role in fat digestion. This can potentially interfere with fat absorption and contribute to paler or greasier stools.

Why does my stool float but look normal?

A brown, formed stool that occasionally floats is often caused by gas trapped within it. This may happen after eating highly fermentable foods or during a period of increased intestinal gas.

Does floating stool always mean fat malabsorption?

No. Research suggests that gas is a more common explanation. Fat malabsorption is more likely when stools are also pale, greasy, oily, bulky, particularly foul-smelling and difficult to flush.

Can anxiety or stress cause floating stools?

Stress can alter bowel motility and worsen IBS symptoms. It may increase diarrhoea, urgency, bloating and gas, which could indirectly make stools more likely to float. Stress does not usually cause persistently greasy or pale stools.

Should I stop eating fat?

Not simply because your stool floats. Fat is an essential part of a healthy diet. If your stools are consistently greasy, pale or oily, seek medical advice rather than severely restricting fat without understanding the cause.

Should I have a SIBO breath test?

A SIBO breath test may be helpful if you experience persistent bloating, wind, nausea and altered bowel habits, particularly after more common causes have been investigated. It should be interpreted alongside your symptoms and medical history.

Book a consultation

If you are concerned about floating stools and would like support with this, you can book a consultation with our sister clinic- ibs-solutions.co.uk

We will explore your symptoms in more detail and put together a clear, tailored plan to help you feel more comfortable and in control again.

If you would rather conduct a test you can order a SIBO test

References

Bouchoucha, M., Devroede, G., Benamouzig, R., et al. (2015). Are floating stools associated with specific functional bowel disorders? European Journal of Gastroenterology & Hepatology, 27(8), 968–973.
This study found floating stools were reported by 26% of patients with functional bowel disorders, compared with 3% of patients with other functional gastrointestinal disorders.

Chen, B., Kim, J.J.W., Zhang, Y., Du, L. and Dai, N. (2018). Prevalence and predictors of small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and meta-analysis. Journal of Gastroenterology, 53, 807–818.
This review supports an association between IBS and positive SIBO testing, although prevalence varies according to the test used.

Shah, A., Talley, N.J., Jones, M., et al. (2020). Small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and meta-analysis of case-control studies. American Journal of Gastroenterology, 115(2), 190–201.
The review found an association between IBS and SIBO but judged the overall evidence to be limited by inconsistent diagnostic methods and imperfect testing.

Ghoshal, U.C., Shukla, R. and Ghoshal, U. (2020). A meta-analysis on small intestinal bacterial overgrowth in patients with irritable bowel syndrome. Journal of Neurogastroenterology and Motility, 26(2), 236–245.
This analysis found IBS patients were more likely to have SIBO when assessed using glucose breath testing or small-bowel culture, particularly in diarrhoea-predominant IBS.

Eswaran, S.L., Chey, W.D., Han-Markey, T., Ball, S. and Jackson, K. (2016). A randomised controlled trial comparing the low-FODMAP diet versus modified NICE guidelines in US adults with IBS-D. American Journal of Gastroenterology, 111(12), 1824–1832.
Both dietary approaches improved symptoms, although the low-FODMAP diet produced greater improvements in individual symptoms such as pain and bloating.

National Institute for Health and Care Excellence (2013). Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel. NICE Diagnostics Guidance DG11.
Faecal calprotectin can help distinguish inflammatory bowel disease from non-inflammatory conditions such as IBS in appropriate patients.

NHS (2026). Coeliac disease: symptoms.
The NHS notes that malabsorption in coeliac disease can cause fatty stools that are greasy, frothy, foul-smelling and difficult to flush.

Frimley Health NHS Foundation Trust (2026). Information for people taking pancreatic enzymes for pancreatic insufficiency.
Pancreatic enzyme insufficiency may cause pale, oily, yellow or orange stools that float, smell offensive and are difficult to flush, sometimes alongside bloating and difficulty maintaining weight.

University Hospitals Coventry and Warwickshire NHS Trust. What is bile acid malabsorption?
Bile acid diarrhoea can cause chronic diarrhoea and the need to open the bowels several times per day; it may be mistaken for diarrhoea-predominant IBS.

Poon, D., Law, G.R., Major, G. and Andreyev, H.J.N. (2022). A systematic review and meta-analysis of the prevalence of bile acid diarrhoea, microscopic colitis and pancreatic exocrine insufficiency in patients labelled with diarrhoea-predominant IBS. Alimentary Pharmacology & Therapeutics, 55(8), 923–936.
This review found that alternative diagnoses, particularly bile acid diarrhoea, may be present in a proportion of patients initially considered to have IBS-D.

Author – Victoria Tyler BSc Hons MBANT

Victoria Tyler owns and runs two busy clinics : Nutrition and Vitality and the IBS and Gut Disorder Clinic.

Nutrition and Vitality, along with the IBS and Gut Disorder Clinic, were founded with the goal of helping patients alleviate IBS symptoms by uncovering and addressing the root causes of their digestive issues.

As a Registered Nutritional Therapist, Victoria holds a BSc (Hons) in Nutritional Therapy and has trained with the Institute of Functional Medicine. She is also accredited by BANT and CNHC.

Before transitioning into health, Victoria earned a degree in Economics and an MBA, working with corporations including Canon and Vodafone. However, her own health challenges led her to pursue a career in Nutritional Therapy.

With a passion for learning, Victoria is committed to staying at the forefront of Functional Medicine. She helps patients manage IBS and other digestive disorders, including SIBO, Candida, and IBD, by identifying and addressing their root causes.

Victoria strongly believes that every symptom has an underlying cause, and there is always a solution to every health condition. To learn more, or to see patient reviews, visit Victoria’s profile on Google.