How 7 Common Diet Plans Can Affect Your Poop, According to Nutritionists

Here’s the scoop: What you eat affects your poop. A high-fiber diet—meaning lots of fruits and veggies—will keep your bowel movements regular. Conversely, a low-fiber diet—consisting mostly of meat and dairy—will probably back up your bowel functioning. We asked nutritionists to explain how seven common diet plans, like keto, Paleo, and intermittent fasting, will likely affect how often you poop. Here's how they broke it all down.

Basically, what you put in has a direct effect on what you push out, which can make changing your diet feel like a gamble for your gut. It’s hard to tell if that trendy eating plan everyone is encouraging you to go on or even one that's recommended for a health condition will leave you unable to poop for days or running to the toilet every five minutes.

Gluten Free Diets

A gluten-free diet involves avoiding foods that contain wheat, barley, or rye. Whether it's a required shift in eating due to a diagnosis of celiac disease or you just want to give it a try, this is a diet that can go two ways.

“Gluten-containing foods like bread, bagels, and pasta can be replaced with versions made with gluten-free grains, like white rice, that are just as processed,” Cynthia Sass, RD, Health contributing nutrition editor, told Health.

Too many processed carbs will likely leave you constipated, but there’s another, more gut-friendly way to go gluten-free, too. “They can also be replaced with whole foods like sweet potatoes, beans, lentils, quinoa, brown rice, and more that are fiber-rich,” Sass explained.

These foods contain insoluble fiber, which does not dissolve in water and can help food move through your digestive system. Insoluble fiber promotes regularity. Other gluten-free sources of insoluble fiber include nuts, seeds, leafy greens, and fruits with edible skins like pears and apples.

Intermittent Fasting

There are several different ways to follow an intermittent-fasting plan, which switches between fasting and eating on a regular schedule. For example, it could mean limiting your eating to a 6- or 8-hour window and then fasting the rest of the day or it could mean eating just one meal a day for a couple of days each week.

Most people who try intermittent fasting don’t see much of a change in their poop, said Julie Upton, RD, Health's registered dietician and writer. However, some people do say they go less frequently. “That’s not a problem. As long as your bowel movements are consistent—once a day or twice a day—there’s no reason to worry if you’re going less frequently,” Upton said.

But remember, you still need to be mindful of what you are eating even if you’re fasting for a portion of the day. If you’re eating a produce-rich, high-fiber diet, intermittent fasting should be a breeze for your bowels.

Keto Diets

On a ketogenic diet, aka keto, you typically follow a diet high in fats, moderate in protein, and very low in carbohydrates. Switching to a ketogenic diet can, however, cause gastrointestinal symptoms, such as constipation.

Going keto can cause constipation because “it's low in fiber and can be high in animal fats and proteins, which are slow to digest." You can consume only 5% to 10% of your daily calories from carbs, and that makes it "very challenging to hit the recommended minimum 25 grams of fiber daily,” Sass explained.

Keto is popular for its ability to aid in weight loss but was originally developed as a treatment for epilepsy and is sometimes recommended for those with seizures that aren't completely controlled by medication.

If you’re set on going keto, Sass recommended incorporating high-fiber, keto-friendly foods like avocados, nuts, berries, and low-carb veggies (think: broccoli and kale) into your daily meal plans. You could also opt to do a modified version of keto that allows for a bit more fiber and a bit less fat.

Mediterranean Diet

Of all the diets on this list, the Mediterranean diet is the one that offers the most positive bowel benefits, Sass said. “Many of my clients who adopt a healthy, whole-foods-based Mediterranean diet can practically set their watches by their bowel movements,” Sass said.

This is because the diet includes a range of plant-based foods, including veggies, fruit, whole grains, nuts, seeds, legumes, and more, Sass explained. “The natural fiber is like a strength training workout for the muscle of the gastrointestinal tract,” she says, “and it tends to respond with regular, healthy bowel movements.”

This primarily plant-based eating plan also includes plenty of olive oil, and animal proteins are eaten in smaller quantities, with an emphasis on fish and seafood. 

In addition to keeping you regular and supporting gut health, research suggests this way of eating has a range of other health benefits. Studies show it can help lower the risk of heart disease, reduce inflammation, and have beneficial effects on glucose (blood sugar) metabolism and insulin resistance to help manage or prevent type 2 diabetes.

Paleo Diet

The Paleo diet, which aims to follow a diet closely resembling that eaten by our ancestors in the Paleolithic era more than 2 million years ago, focuses on lean meats, fish, fruits, vegetables, nuts, and seeds. 

How Paleo affects your poop will depend on what your diet was like before you went on this diet plan. “If going Paleo significantly ups your intake of veggies and berries, it may result in healthier poop,” Sass said.

On the other hand, because Paleo does away with grains and pulses, it could slow your digestion if you’re already used to eating a lot of fiber. Upton advised drinking lots of water and eating non-starchy fruits and veggies to help move things along.

Whole30

The Whole30 plan is meant to change how you think about food for 30 days by getting rid of bad eating habits, boosting metabolism, and eliminating foods that cause inflammation.

If you’re used to eating a traditional low-fiber American diet—meaning not many fruits, veggies, and whole grains and lots of sugar and processed carbs—switching to this veggie-heavy diet may trigger diarrhea, Upton said. “The diarrhea is not a health threat, and your GI tract will get used to the higher fiber content in time,” Upton explained.

Sass pointed out, however, that if you are used to eating a high-fiber diet, then cutting out pulses (like beans, lentils, and chickpeas) and whole grains may slow digestion.

Another thing to keep in mind: Whole30 is also dairy-free, meaning “your digestive health may depend on how your body was reacting to the dairy you were eating,” Sass said. “For example, if you're lactose intolerant or have a dairy sensitivity, cutting it out may resolve diarrhea or constipation.”

Vegan Diets

There are different ways to practice veganism. “A vegan diet can be loaded with vegan junk food, refined sugar, and processed carbs with few veggies and whole foods,” Sass said, which makes it a recipe for constipation. “But a healthy vegan diet that includes plenty of veggies, fruits, whole grains, nuts, seeds, and pulses can make for incredibly healthy poop.”

Following a produce-heavy vegan diet may also help protect against certain diseases. A systematic review and meta-analysis published in 2017 in Critical Reviews in Food Science that found that vegan diets helped reduce the risk of cancer by 15% and vegetarian or vegan eating reduced the risk of ischemic heart disease (heart weakening due to reduced blood flow) by 25%.

A Quick Review

Eating whole, plant-based foods every day is the secret to staying regular and supporting general health. Any change in diet can change the frequency and consistency of your stool.

How a diet affects your poop may depend on what you were eating previously and which foods you are adding.