Here’s the scoop: What you eat affects your poop. A high-fiber diet, meaning lots of fruits and veggies, will keep you regular, while a low-fiber diet, consisting mostly of meat and dairy, will probably back up your bowels.
Basically, what you put in has a direct effect on what you push out, which can make trying a new diet feel like a gamble for your gut. It’s hard to tell if that trendy new weight-loss plan everyone is encouraging you to go on will leave you unable to poop for days on end, or worse, running to the toilet every five minutes.
That’s why we asked nutritionists to explain how 7 of today’s most popular diet plans, like keto, Paleo, and intermittent fasting, will likely affect how often you go number two. Here’s how they broke it all down.
Of all the diets on this list, the Mediterranean diet is the one that offers the most positive bowel benefits, Cynthia Sass, RD, Health contributing nutrition editor, tells Health. “Many of my clients who adopt a healthy, whole foods based Mediterranean diet can practically set their watches by their bowel movements,” Sass says.
This is because the diet includes a range of plant-based foods, including veggies, fruit, whole grains, nuts, seeds, legumes, and more. she explains. “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.”
Sass says the ketogenic diet, aka keto, can cause constipation because “it’s low in fiber and can be high in animal fats and proteins, which are slow to digest.” Keto followers can consume just 4% to 5% of their daily calories from carbs, and that makes it “very challenging to hit the recommended minimum 25 grams of fiber daily,” she explains.
If you’re set on going keto, Sass recommends 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 carbs and a bit less fat.
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, Julie Upton, RD, tells Health. “The diarrhea is not a health threat, and your GI tract will get used to the higher fiber content in time,” Upton explains. Sass points 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 says. “For example, if you’re lactose intolerant or have a dairy sensitivity, cutting it out may resolve diarrhea or constipation.”
Again, 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 says. 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 advises drinking lots of water and eating non-starchy fruits and veggies to help move things along.
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 says, 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.”
Most people who try intermittent fasting don’t see much of a change in their poop, Upton says. 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,” she says.
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.
This is another 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,” says Sass. 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,” she explains.
Bottom line: Eating whole, plant-based foods every day is the secret to staying regular.