Dr. Anthony Gustin is a board-certified sports chiropractor, functional medicine practitioner, entrepreneur, podcast host, and founder of Perfect Keto.
Let’s come right out and say it: a ketogenic diet can change the way you poop.
Keto has a lot of great benefits — weight loss, heart health, mental clarity, clear skin, and so on. But during the transition into ketosis, your body can struggle to adapt to your new low-carb diet. You may experience constipation, diarrhea, frequent bowel movements, and other changes to your digestion.
The good news is that you’re not alone. The low-carb community calls this phenomenon “keto poop.” It’s a common side effect of starting keto, there’s plenty you can do about it, and it’s temporary.
There are a lot of long-term digestive benefits to a ketogenic diet. Once you stabilize your bowel movements and get used to this new way of eating, keto is great for your gut.
Here’s a look at what causes keto poop, how you can stop it from happening, and how long-term keto is good for your digestion.
When you start a keto diet, you may experience one of two things, digestively speaking (especially if you’re coming from a low-fat, high-carb diet):
- Trouble pooping (constipation)
- Excessive pooping (diarrhea)
Let’s start with constipation.
Keto and Constipation
First things first, not pooping every day is not a sign of constipation. You can poop anywhere from three times a day to once every three days and it’s considered normal.[*]
It’s when there is a sudden change in the frequency of your pooping habits along with a difficulty in pooping (a.k.a. your poop is hard and dry) that constipation becomes a concern.
The three main causes of keto-related constipation are:
#1: Low Fiber Intake
When you start keto, you often cut out a lot of high-fiber foods: whole grains, higher-carb veggies, legumes, beans, and so on. As a result, you can end up deficient in fiber. Fiber adds bulk to your stool and helps keep you regular. And when you don’t get enough of it, you can become constipated[*].
The solution: Eat more vegetables. Get plenty of low-carb greens like broccoli, cauliflower, bok choy, fennel, kale, collards, and cabbage. Blackberries, raspberries, and strawberries are also great sources of fiber, and they’re low in sugar.
You can expect to lose 3-7 pounds of water weight during your first couple weeks of keto. The drop happens because you’re working through your glycogen (carb stores), and carbs require a lot of water for storage, while fat does not.
If you lose all that water and don’t replace it, you can end up with constipation. If your stools are dry and hard, you may be dehydrated.
The solution: Double down on your water intake to fix the issue.
#3: Electrolyte Imbalance
When you stop eating carbs, your insulin levels stay low and steady. That’s great for your health, but it causes your kidneys to expel sodium, magnesium, and potassium instead of holding onto them[*].
Electrolytes (especially magnesium) pull water into your intestines, which softens dry stools and makes them easier to pass[*].
The solution: To improve your electrolyte balance and relieve constipation, make sure you salt your food liberally, get plenty of veggies, and take 200-400 mg of magnesium daily. Magnesium citrate and magnesium glycinate are the two best forms. Magnesium citrate will help you most with constipation — just be sure you don’t take more than 400 mg, or you may get diarrhea. For potassium, try these 12 potassium-rich foods you can enjoy on keto.
Eating more veggies, drinking more water, and prioritizing electrolytes will fix keto constipation in most cases.
Keto and Diarrhea
Keto can also cause diarrhea, especially during the first couple weeks of the diet. Keto diarrhea happens for three main reasons:
#1: Low Digestive Enzymes
Your liver makes bile and digestive enzymes to emulsify fat and digest it, but when you start eating far more fat than your body is used to, it can take your liver a little while to catch up with its bile and digestive enzyme production.
Until it adjusts to your new high-fat diet, you can end up with diarrhea because of undigested fat.
The solution: If you’re just starting keto and you have diarrhea, take lipase, an enzyme that breaks down fats, for the first week of eating keto. Lipase will help you metabolize the extra fat. Your digestion should adjust on its own by the end of the first week.
#2: Low Fiber Intake
Paradoxically, low fiber intake can cause both constipation and diarrhea. Without fiber to slow down digestion, food can go right through you.
The solution: If you have diarrhea, try eating more low-carb vegetables to keep your digestion moving at a healthy pace.
#3: Too Many MCTs
A lot of keto dieters use medium-chain triglycerides (MCTs) to get extra energy and a boost in ketone levels. MCTs are great for you, but they can cause urgent diarrhea if you eat too many of them.
The solution: If you find MCTs give you diarrhea, limit yourself to a teaspoon of MCTs at a time when you’re starting out. You can gradually work your way up to ~2 tablespoons over the course of a week or so.
Use these tips to prevent constipation and diarrhea during your keto transition. Once your body adjusts to your new diet, you likely won’t have any digestive issues going forward.
3 Main Ways Keto Improves Digestion
In fact, long-term keto is great for your digestion. A high-fat, low-carb diet is particularly good for your gut bacteria and your gut lining, both of which play a major role in your overall health. Here’s how keto improves your digestion.
#1: Keto Feeds Good Gut Bacteria
Your gut microbiome is filled with trillions of bacteria that influence your digestion, metabolism, and even mood and brain function.
There are thousands of different species of bacteria in your gut, and they change according to your diet and environment. Not all those bacteria are friendly, though. To keep your gut in good shape, you want to feed good bacteria and discourage damaging bacteria.
Plus, on a well-balanced keto diet, you’re getting virtually all your carbs from vegetables. Veggies are a great source of prebiotic fiber, which serves as food for your good gut bacteria and helps them flourish[*].
Both dietary fat and prebiotic fiber also increase short-chain fatty acids in your gut, which decreases intestinal inflammation and protects your gut from damage[*].
#2: Keto Starves Bad Gut Bacteria
Keto also starves bad gut bacteria. Most pathogenic bacteria run on sugar, particularly fructose[*]. A diet high in sugar, especially in the form of high-fructose corn syrup, feeds damaging gut bacteria, giving them the fuel to multiply and colonize your gut[*].
Eating a high-fat diet without carbs starves bad gut bacteria, killing them off and making room for good gut bacteria to grow.
#3: Keto Maintains Gut Integrity
Sugar (again, fructose in particular) is also bad for your gut lining. Sugar damages your intestinal barrier by weakening little seams called tight junctions[*]. Tight junctions prevent food particles, bacteria, and other contents of your gut from leaking into your bloodstream. When your tight junctions weaken, you can end up with gut inflammation and an unnecessary immune response, which causes digestive issues and intestinal damage[*].
On a keto diet, you aren’t eating sugar or other refined carbs, so you don’t have to worry about sugar intake damaging your gut lining.
The Takeaway: Is Keto Poop Something You Should Worry About?
If you have constipation or diarrhea when you’re starting keto, don’t worry — your body is just adapting to your new diet. It can take a little experimenting to find the right balance of fat, protein, and fiber for your body.
Eat fiber-rich vegetables, drink plenty of water, and, if you have to, take digestive enzymes or electrolyte supplements to regulate your digestion.
Keto poop is usually temporary, but if your digestive issues last more than a couple of weeks, keto may not be for you.
Consider adding more carbs and fiber, or try switching to a variation of keto, like cyclical keto or targeted keto. With a little trial and error, you’ll find a diet that makes you look and feel great.