Gut basics
What is gut motility? Why slow or fast digestion causes symptoms
Gut motility is the coordinated muscle movement that mixes food and carries it through the digestive tract. When it is too slow, the result is fullness, bloating, reflux or constipation. When it is too fast, the result is cramps and loose stools. Disordered motility is one of the commonest reasons for gut symptoms with normal reports.
In short
- The gut moves food by waves of muscle contraction controlled by its own nervous system.
- Between meals, a “housekeeping” wave sweeps the stomach and small intestine clean about every 90 minutes to two hours.
- Slow movement and fast movement cause different symptoms, and sometimes both occur in the same person.
- Motility can be measured, and treatment depends on which part of the gut is affected.
How does the gut move food?
Peristalsis
A ring of muscle tightens behind the food and relaxes ahead of it, pushing it forward.
Mixing
Back-and-forth contractions churn food with digestive juices and bring it into contact with the lining.
The housekeeping wave
During fasting, a strong wave travels from the stomach to the end of the small intestine and clears leftover food and bacteria. Constant snacking interrupts it.
The meal reflex
Food entering the stomach signals the colon to contract, which is why the urge to pass stool often follows a meal.
What happens when motility is slow?
| Where | What you feel |
|---|---|
| Food pipe | Food sticking, chest discomfort, regurgitation |
| Stomach | Fullness after a few mouthfuls, nausea, vomiting of old food, reflux |
| Small intestine | Bloating; bacteria overgrow when food lingers |
| Colon | Hard, infrequent stools |
| Pelvic floor | Straining and incomplete emptying, because the muscles do not relax |
What happens when it is fast?
Food and fluid reach the colon before the small intestine has finished absorbing them. The result is cramping, urgency and loose stools, often soon after eating.
What disturbs motility?
- Diabetes, which can damage the nerves of the stomach and bowel
- Thyroid disorders: an underactive thyroid slows the gut and an overactive one speeds it
- Medicines: strong painkillers, some medicines for depression and bladder problems, iron, and medicines that slow stomach emptying for weight loss or diabetes
- A past gut infection, after which the gut’s nerves remain over-sensitive
- Stress and poor sleep, acting through the gut-brain connection
- Surgery on the stomach or bowel
- Too little fibre, fluid or physical activity
How is motility tested?
- Oesophageal manometry for the food pipe
- A stomach emptying scan when slow emptying is suspected
- Breath tests for bacterial overgrowth, which often accompanies slow movement
- A transit study, in which swallowed markers are tracked on X-ray, for slow colon movement
- Anorectal manometry for the pelvic floor
An endoscopy is done first where needed, to make sure there is no physical blockage.
How is it treated?
Meal pattern
Smaller meals at regular times, eaten slowly, with gaps of three to four hours between them so that the housekeeping wave can do its work.
The right fibre
Soluble fibre such as isabgol for constipation; less fat and fibre for a slow stomach.
Movement
A walk after meals, and daily physical activity.
Medicines
Medicines that speed or slow the gut, chosen by which part is affected, and a review of any that may be causing the problem.
Retraining
Biofeedback for pelvic floor muscles that do not relax.
The gut-brain connection
Slow breathing, sleep correction and stress practice improve the nerve signals that pace the gut.
When should I see a doctor?
See a doctor for repeated vomiting, food sticking on swallowing, weight loss, a new change in bowel habit lasting more than three weeks, or blood in the stool. A blockage must be excluded before symptoms are put down to motility.
Questions patients ask me
Can I have slow and fast motility at the same time?
Yes. A slow stomach with a fast colon, or constipation alternating with loose stools, is common in irritable bowel syndrome.
Does snacking through the day affect motility?
The housekeeping wave runs only during fasting. Frequent snacking keeps interrupting it, which may contribute to bloating in some people. Leaving a few hours between meals helps.
Is slow digestion the same as constipation?
Not always. The stomach can empty slowly while the colon works normally, and the other way round. The symptoms tell them apart.
Sources
This page is written for patients and is based on the guidelines and studies below. It is for education and does not replace a consultation.
- American College of Gastroenterology guideline on gastroparesis. Camilleri M et al. Am J Gastroenterol. 2022. PubMed 35926490
- American Gastroenterological Association and American College of Gastroenterology guideline on chronic constipation. Chang L et al. Gastroenterology. 2023. PubMed 37211380
- Chicago Classification version 4.0 of oesophageal motility disorders. Yadlapati R et al. Neurogastroenterol Motil. 2021. PubMed 33373111
- Review of the enteric nervous system. Furness JB. Nat Rev Gastroenterol Hepatol. 2012. PubMed 22392290