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Intermittent fasting may cause constipation, diarrhea or much bigger poops than usual.
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From weight loss to decreased inflammation, intermittent fasting has been linked to a plethora of positives for your body and overall health. But it can come with some unexpected side effects, too — like poop problems. That's right, IF may throw your bowels off balance.


Here, Niket Sonpal, MD, a New York-based internist and gastroenterologist, discusses three ways your bathroom habits may shift during intermittent fasting.

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1. You’re Constipated

"Constipation can be a common side effect of fasting because nothing is being consumed or helping to move the previous meal through your digestive system [during your fasting window]," Dr. Sonpal says.

This issue may be more common for people who have slow-moving digestive tracts, Dr. Sonpal adds. For these folks, eating more frequently helps things run smoothly.

Another possible explanation for being backed up? You're not getting enough fiber during your fast, Dr. Sonpal says. Think about it: If your eating window is limited, and you're consuming less overall, your fiber intake may take a hit. Fiber is fundamental for proper bowel function because it both adds bulk and softens your stool, which makes your poop easier to pass, per the Mayo Clinic.


If you're flushing less frequently, don't fret. "As long as there is no discomfort, having fewer bowel movements is not necessarily a concern when starting a fast," Dr. Sonpal says.

Fix it:‌ If a lack of fiber within your eating window is the main culprit for your constipation, make food choices to ensure you're getting all the nutrients your body needs, Dr. Sonpal says. Pile your plate with fruits, veggies and whole grains, which are stellar sources of fiber.


"The key thing with intermittent fasting is understanding the importance of fiber-rich produce as opposed to the misconception that a narrower window of eating nothing but chips and cookies will improve your health," Dr. Sonpal says.


Frequency of bowel movements may also be determined by conditions a person may have, medications they may be taking, stress and lack of exercise, among other things, so speaking to your internist or gastroenterologist may help clarify questions unique to your health history,” Dr. Sonpal says.

2. You Have Diarrhea

Conversely, intermittent fasting may bring on watery poops for some people. Indeed, in the beginning stages of intermittent fasting, diarrhea can be a common side effect.



Here's why: "While fasting, the colon contracts more and removes any waste that may get clogged with constant food consumption," Dr. Sonpal says. In other words, as your gut gets rid of all its junk, you may experience runny stool.

Diarrhea during fasting may also occur because of an over-secretion of water and salts in the digestive tract, Dr. Sonpal says. Drinking liquids with high concentrations of caffeine (sorry, coffee lovers!) may trigger this chain reaction.


"While diarrhea is very unpleasant, it is likely not life-threatening," Dr. Sonpal says. "However, if the diarrhea is accompanied by bloody stool, pain and swelling around the bowel and lasts several days, it might be worth calling a doctor."

Fix it:‌ "Because diarrhea significantly decreases hydration levels, studies have shown that drinking water throughout the day relieves diarrhea symptoms and prevents dehydration," Dr. Sonpal says.


"Also, consider taking probiotics, either through probiotic food or supplements, which can help restore balance to the GI tract by increasing the level of good bacteria," he adds. "While probiotics don't guarantee relief, they can help shorten a bout of diarrhea."

Upping your fiber or using over-the-counter anti-diarrheal medications like loperamide and bismuth subsalicylate (Pepto-Bismol) can also give you a respite from the runs.


3. You Have Larger Bowel Movements

"In general, bowel movements are dependent on what foods are consumed [and, consequently], any changes in diet will result in a temporary change in bowel habits as well," Dr. Sonpal says.

So, for example, if you've decided to overhaul your diet during your fasting journey, and you're consuming loads of fiber-rich fruits and veggies every day, you might notice larger poops (remember, fiber bulks up your bowel movements).

Fix it:‌ Don't forgo the fiber. For one, most people don't get enough daily. In fact, 95 percent of Americans don't consume the recommended daily amount of fiber, according to a July 2016 article in the American Journal of Lifestyle Medicine.‌ ICYDK, the 2015-2020 Dietary Guidelines for Americans suggest getting between 25 and 34 grams a day if you're under 50, or 22 to 28 grams if you're over.

And secondly, fiber keeps your GI tract functioning properly and promotes regular, healthy poops. So, as long as you're not experiencing any discomfort, embrace your big poops.

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