Fast Bowel Movement – Causes of Faster Passing of Stool

There is continuous movement throughout the gut. It starts from the moment we swallow food and continues all the way through until we pass out stool. The speed of this movement changes in different parts of the gut and sometimes it can be upset. The movement speeds up or slows down and as a result it causes symptoms like diarrhea or constipation, respectively.

How fast should bowel movements be?

The term bowel movement usually refers to passing stool but it also refers to the movement through the bowels and gut as a whole. Remnants of food that is eaten anywhere between 24 to 72 hours prior is eventually passed out as stool along with wastes and others substances.

The time that it takes to pass out as stool from when it was consumed is known as bowel transit time. For adults, the average time is approximately 53 hours while in children it is about 33 hours. Movement through the large intestine alone can take on average about 40 hours in adults, and is found to be slower in women.

Any bowel movement that occurs immediately after eating or shortly after a meal is not composed of food that was consumed just prior. This is a common misconception. However, bowel motility may be much faster in diarrheal illnesses and much slower when a person is constipated.

Read more on bowel motility disorders.

The term diarrhea specifically refers to having more than three bowel movements in a day, and passing watery stool. All of these features are signs of fast bowel movements.

Faster Than Normal Bowel Movements

Sometimes movement through the bowels are faster than normal. This rapid bowel motility usually results in diarrhea. However,  the underlying cause of the faster bowel motility may also cause diarrhea. Nevertheless, it is important to understand how fast movement results in diarrhea.

Normally the movement through the bowel is at a speed that allows for proper digestion and absorption of food. The time varies in different parts of the gut. For example, it may take about 6 hours for food to pass through the stomach but as long as 40 hours to pass through the large intestine.

Mechanical and chemical digestion occurs mainly through the course of the stomach and small intestine. Water is pumped out of the body and into the small intestine to aid with digestion. Almost all nutrients are absorbed within the small intestine.

The liquid chyme then enters the large intestine, containing water, undigested food and wastes. As it passes through the large intestine water is reabsorbed back into the body. Eventually soft solid stool is formed which is then passed out during defecation.

However, when the movement through the bowels is faster than normal then:

  • Food is not properly digested and the undigested nutrients may draw out more water than normal from the body.
  • Water is not thorougly reabsorbed in the colon thereby preventing the stool from becoming soft but solid. Instead the stool is liquid or watery.

In diarrheal illnesses, the bowel walls may be inflamed or damaged. This further hampers digestion, causes more water to leak out and blocking water reabsorption. All of these effects play a role in fast bowel movements with loose and watery stool.

Read more on watery bowel movement.

Causes of Fast Bowel Movements

As discussed, fast bowel movements are usually associated with diarrheal illnesses. Diarrhea is a symptom that can occur with a number of diseases. However, diarrhea may also occur with dietary and lifestyle factors as well as for no clearly identifiable reason. A sudden change in bowel habit should always be investigated by a medical practitioner, especially if persists and is worsening over time.

Diarrhea Diseases

Some of the possible diseases that may present with diarrhea include:

  • Infections (viruses, bacteria, protozoa) – gastroenteritis or enterocolitis.
  • Inflammatory bowel disease – Crohn’s disease or ulcerative colitis.
  • Food intolerances, such as lactose intolerance.
  • Malabsorption syndromes, such as fructose malabsorption.
  • Celiac disease.
  • Medication such as antibiotics (antibiotic-associated diarrhea).

Diet and Lifestyle

Dietary and lifestyle factors can also speed up bowel movements and even lead to diarrhea. This may occur with:

  • Overeating
  • High fiber intake
  • Exercise
  • Rapid rehydration
  • Alcohol
  • Stimulants like nicotine or caffeine


Functional diarrhea is frequent and loose bowel movements that are not due to any disease or dietary and lifestyles factors. The exact cause is unknown but it is believed to be due to faster than normal bowel motility. The reason why this occurs in some people is unclear. It is commonly seen in diarrhea-predominant irritable bowel syndrome (IBS-D) and may be accompanied by abdominal pain and cramps.

After Eating

As mentioned, a bowel movement after eating may occur in several conditions. However, the stool in these bowel movements following a meal is not comprised of the food that was just eaten. The reason for bowel movements after eating has to do with nerve reflexes. There are several specific nerve reflexes that control defecation. Therefore these reflexes are referred to as the defecation reflex.

Two of these defecation reflexes may be responsible for a bowel movement after eating. The gastrocolic reflex is initiated by stretching of the stomach, usually with food. This stimulates movements in the colon. The duodenocolic reflex has the same effect on the colon when there is food in the duodenum (small intestine). If these reflexes are overactive then a person may have a bowel movement shortly after eating, if not immediately after a meal.

With Juicing

Juicing has become a popular health and weight loss trend. It involves juicing fruits and vegetables and consuming the juice in place of meals. One of the common consequences with juicing is more frequent bowel movements. Sometimes the stool may be loose or watery, as is typicaly of diarrheal stool. Faster bowel movements from juicing occurs for several reason.

Liquids naturally move through the gut faster than solids, especially if there is insufficient solid food intake. There is also an increased fiber intake with a diet high in fruit and vegetables. Some people who are sensitive to fructose, fruit sugar, may experience gastrointestinal disturbances such as diarrhea due to the fruit intake. Lastly, fresh fruit and vegetable juice may become easily contaminated with bacteria which can then cause infectious gastroenteritis or enterocolitis.

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