Sometimes you feel immediately hungry after eating. Other times, you’ll stay full for hours. It’s all related to how quickly your digestive system is working.

The digestive system involves multiple stages and organs. ‘It begins with chewing food, where saliva is added to help digestion, and ends with a bowel movement,’ says Lance Uradomo, M.D., an interventional gastroenterologist at City of Hope Orange County in Irvine, California.

The whole process, from when you eat something to when it comes out the back end, is also referred to as the whole gut transit time or gastrointestinal motility. How long this process takes can vary a lot depending on someone’s health, diet, age, exercise habits, stress levels, and other factors, Dr. Uradomo explains.

Here’s what you should know about how long it takes to digest food and what your gut transit time can tell you about your health.

How Long Does It Take to Digest Food?

The digestive process includes several steps, according to the National Institutes of Health:

• Gastric emptying is the time it takes for food to move through your stomach into the small intestine. This can take a few minutes to up to about six hours.
• Small bowel transit time is how long it takes food to move through the small intestine. This may take two to eight hours.
• Colonic transit time, which is the time it takes for food to move through your large intestine. This is the longest process and may take 48 to 72 hours.

‘It’s highly variable depending on the nature of food and contents in the gut,’ says Arthur Beyder, M.D., a gastroenterologist and spokesperson for the American Gastroenterological Association.

The whole gut transit can take between 10 and 73 hours, research shows. A 2023 study published in the journal Gut suggests that the median time is 28 hours for healthy people.

However, the process could take up to five days in some cases, explains Christopher Cao, M.D., a gastroenterologist and assistant professor at the Icahn School of Medicine at Mount Sinai.

What Factors Affect Transit Time?

Diet plays the biggest role in gut transit time.

‘Foods that are high in fat, such as peanut butter, eggs, or meat, take longer to get through the stomach than lighter foods such as pasta,’ Dr. Uradomo says. ‘Water goes through the stomach in 10 to 20 minutes, and other liquids, such as smoothies, may take up to an hour.’

High-fibre foods, like fruits, vegetables, and whole grains, can slow down digestion and help you feel full. Dr. Beyder says these foods can take longer to empty from the stomach and go through the small bowel. Fibre also keeps you regular by bulking and softening your stool, making it easier to pass.

‘That’s this dual nature of fibre,’ Dr. Beyder adds. ‘It allows you to have both regular normal bowel movements that are not constipation but also reside in the colon for longer times.’

Other things you consume affect the speed, too. Caffeine can speed things up, while alcohol can slow motility, Dr. Cao adds.

Certain medical conditions, like diabetes or hypothyroidism, can interfere with motility, Dr. Uradomo says. So can a sedentary lifestyle, stress, and medications like antacids and opiates. Age slows down your digestive system.

Does Knowing Your Gut Transit Time Really Matter?

Not really, doctors say, unless you have symptoms like bloating, diarrhea, or constipation.

‘For us, it’s just a matter of patient symptoms,’ Dr. Beyder says. ‘We do not have direct evidence that modulating transit time changes any health parameters.’

However, slow motility could signal a GI disorder like gastroparesis or chronic constipation, he explains. That’s why it’s important to pay attention to additional symptoms, like pain and bloating.

And, a 2021 study suggested that gut transit time was a ‘more informative marker’ of gut microbiome function compared to stool consistency and frequency.

There’s just such a wide variance of what’s normal when it comes to gut transit time, Dr. Cao says. One bowel movement every three days to three bowel movements daily can be considered normal.

Since diet plays a role, your whole gut transit time might be slower or faster from week to week. But if you notice drastic changes in your bowel habits that last several days, see your doctor, Dr. Uradomo says.

How to Test Your Whole Gut Transit Time

If you’re curious about your gut transit time, there are a couple of ways to test it out. Eating corn or muffins with blue dye and tracking how long it takes to show up in your poop are some non-scientific options.

However, Dr. Cao says, ‘It’s worth noting that these tests do not evaluate for other causes of abnormal bowel movements like intestinal obstruction or dyssynergic defecation, and do not check for underlying causes of decreased GI motility.’

So it’s best to talk to your doctor before trying this out, Dr. Beyder says. Doctors can also perform bowel transit time tests if they suspect you have a medical condition affecting your ability to pass stool.

For instance, a gastric emptying study involves swallowing a radioactive tracer, which is tracked by imaging. Dr. Cao says it may be used to evaluate stomach motility when you have chronic nausea or seem to feel full quickly.

A colonic transit study involves swallowing radiopaque markers, which are tracked using X-rays. It may be used to evaluate for constipation.

Keep in mind, though, that constipation, nausea, and other GI symptoms can be caused by a variety of health conditions, not just delayed bowel transit time, Dr. Cao notes.

When to Worry

Sudden bowel habit changes, blood in your stool, unintentional weight loss, or abdominal pain should signal a trip to your doctor, Dr. Cao says. Also see a doctor if you struggle to have a bowel movement or if your bowel habits are affecting your daily life, Dr. Beyder says.

Paying attention to these symptoms is especially crucial as rates of colon cancer are climbing among people 55 and younger, Dr. Uradomo says. ‘It’s important to get your recommended colon cancer screenings and see your doctor right away at the onset of any of these symptoms.’