Overactive Bowels – Meaning, Causes and Tests

We are all accustomed to a certain level of bowel activity or a specific bowel habit which tends to vary among individuals. Some people pass stool daily, or even more than once in a day. Others pass every second day or even infrequently. These variations are not considerd abnormal provided that the regularity of bowel movement does not fall within the definition of constipation or diarrhea. However, there are times where bowel habit may change for periods of time for a number of known and unknown reasons.

What are overactive bowels?

Overactive bowels is a common term for passing stool more frequently than normal. At the extreme is diarrhea which is defined as having more than three bowel movements in a day. Typically diarrheal stool is loose and watery in nature. Overactive bowels is not a specific medical term and can therefore have several meanings. Apart from more frequent than normal bowel movements, overactive bowels may also describe excessive bubbling or growling sounds from the gut which is also known medically as borborygmi.

Although common terms like overactive bowels are used quite loosely it is important to understand that these changes in bowel activity may not in fact be an alteration that can be considered as normal. In fact it may be the start of a symptom like diarrhea or even a very mild case of diarrhea. Some people do have more frequent bowel movements than others and while this heightened activity can seem to be abnormal, it may not clearly fall within the category of diarrhea.

Causes of Overactive Bowels

The causes of overactive bowels can vary from dietary and lifestyle factors to diseases and even with the use of certain drugs or supplements. It is important to first understand what the term overactive bowels may mean to the individual since this is highly subjective term that is not a medical diagnosis. Where diarrhea is the symptom, it should be labeled as such since using terms like ‘overactive bowels’ can be misleading and even confusing at times. This can hamper efforts to identify an underlying cause of overactive bowels and treat it accordingly.

The most likely causes of overactive bowels has been discussed below. It is possible that this fluctuation in normal bowel habit may be dueto other conditions such as colon cancer and so on. Medical attention is always advisable.

Changes in Diet

Most of us have adapted to a specific diet where we consume foods and drinks that we are accustomed to. This is largely determined by affordability, availability, cultural tastes and individual preferences. Variations in diet can sometimes cause a change in bowel habit. It is more pronounced when eating larhe amounts of unusual foods or when consuming spicy meals that tend to irritate the gut. High fiber foods, excessive fluid intake and foods or beverages with stimulants like caffeine can also contribute to overactive bowels.

Excessive Physical Activity

Physical activity can also alter bowel habit and exercise is therefore recommended as one of the ways to treat constipation. However, excessive physical activity for a person can also trigger more frequent bowel movements and diarrhea. One such case is runner’s diarrhea. This alteration in bowel activity can happen with any type of exercise. It occurs for a number of reasons such as increased bowel motility with physical activity and increased pressure within the abdomen.

Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a functional bowel disorder where the bowel motility may be faster than normal as is the case in IBS with diarrhea. As a result a person may find that they have very frequent bowel movements. Diarrhea may only be present during acute flareups. There is no underlying disease in irritable bowel syndrome. Rather the problem lies in abnormal bowel motility which refers to the muscle contractions of the intestinal walls that facilitate movement through the bowels.

Diarrheal Illnesses

A number of diseases may cause diarrhea as a symptom. In milder forms of these diseases there may not be diarrhea but rather freqeunt bowel movements which may be termed as overactive bowels.

  • Food intolerances like lactose intolerance where the body has difficulty digesting nutrients like lactose (milk sugar).
  • Gallbladder disease like gallstones where the outflow of bile from the gallbladder is impaired.
  • Gastroenteritis which is mainly due to infections with viruses, bacteria or protozoa or its toxins. Also known as food poisoning.
  • Hyperthyrodism where high levels of thyroid hormones raises the metabolic rate.
  • Inflammatory bowel disease (IBD) where the immune system attacks the lining of the bowel and causes inflammation.
  • Intestinal worms which infest the bowels and consume nutrients from foods that are eaten.
  • Pancreatic exocrine insufficiency where the pancreas does not release its enzymes for digestion.

Drugs and Supplements

A number of different drugs and supplements may cause an increase in the frequency of bowel movements or even lead to diarrheaas a side effec. This depends on the type of drug or supplement, quantity used and individual sensitivity to substances. Some of the more common drugs and supplements that may cause overactive bowel movements include:

  • Antibiotics
  • Antacids
  • Chemotherapy
  • Laxatives
  • Herbs like senna
  • Castor oil and other purgatives
  • High dosese of nutritional supplements like vitamin C

Tests for Overactive Bowels


It has to firstly be ascertained whether overactive bowels are a problem that requires medical intervention. Frequent bowel movements with well formed, soft but solid stool is not usually a cause for concern if it is not affecting daily life. Similarly overactive bowels without other symptoms may not be a problem especially if it is short-lived or persisting but not worsening. However, a sudden change in bowel habit where the bowels become overactive may warrant further diagnostic investigations such as:

  • Barium enema
  • Colonoscopy
  • Fecal occult blood test
  • Stool analysis

The results of these tests will provide an indication for the possible cause of overactive bowels. However, there are times where all test results are within the normal range but a person is experiencing overactive bowels and associated symptoms. This may be seen with functional bowel disorders like irritable bowel syndrome (IBS).

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