Does Fiber Cancel Out Carbs Keto

Embarking on a keto diet involves cutting high carbohydrate foods out of your diet in exchange for what’s often steady weight loss without feeling hungry. 

But keto dieters are still allowed a small number of precious carbohydrates per day. So, many people wonder, does fiber cancel out carbs on keto? Since every gram of carbohydrate counts, we’ll help you understand the relationship between fiber and carbohydrates.

Fiber’s Role in Net Carbs

Here’s the good news: fiber doesn’t count towards your net carb intake when following a keto diet. However, it doesn’t flat-out cancel your carbohydrate intake.

You should aim to consume both soluble and insoluble fiber on the keto diet, with the difference being whether they’re water-soluble. 

Although fiber doesn’t count in your carbohydrate intake while on the keto diet, the reality is that many fibrous foods come with significantly more carbs than fiber. Many high-fiber foods also fall on the high end of the glycemic index, meaning they spike blood sugar levels.

So, avoiding high fiber and high glycemic foods is essential to prevent throwing away your hard work to get into ketosis.

If you’re unsure about how much fiber a food contains, the Fiber Content Calculator is an excellent free tool to guide you.

Fiber-Friendly Foods To Eat on a Keto Diet

Below are some excellent fiber-rich foods you can eat on a keto diet. Remember, only the grams of carbs from fiber don’t count when figuring out your net carb intake.

Therefore, it’s still important to monitor your vegetable intake and count any carbohydrates over the fiber intake as part of your total daily carbohydrate consumption, if applicable.

  • Chia seeds
  • Lettuce
  • Almonds
  • Tomatoes
  • Cruciferous vegetables

If you’re scratching your head about what cruciferous vegetables are, they’re veggies like broccoli, Brussel sprouts, and bok choy.

Fibrous Foods To Avoid on a Keto Diet

When asking yourself, “Does fiber cancel out carbs on keto?” that’s often not the case. Most foods contain more carbohydrates than fiber. So, any carbohydrates you eat over the total fiber content in grams must count towards your daily keto net carb allowance.

Below are some fibrous foods that can quickly put a damper on your keto diet:

  • Beans
  • Lentils
  • Potatoes
  • Carrots

That’s not to say that you can never eat these foods when you’re on a keto diet; most people consume 20 to 50 grams of carbohydrates daily.

However, you’ll get more bang for your fiber and carbohydrate buck by sticking with foods on our keto fiber-friendly list.

Taking a Fiber Supplement To Offset Carbs

You might wonder, can you take a fiber supplement to offset your carbohydrate intake while following a keto diet?

Unfortunately, it doesn’t work that way. If it did, you’d be able to eat a dozen donuts before downing a fiber supplement to undo the equivalent amount of carbohydrates you consume. 

Instead, fiber is a carbohydrate, but one that the body can’t digest. So, when you eat food with fiber in it, your body won’t absorb the number of grams of fiber that food contains.

Therefore, even though the fiber in your food is technically a carbohydrate, your body doesn’t register it as such since it can’t break it down. 

So, it passes through your system without counting towards your keto net carb count, but it can’t undo any other forms of carbohydrates you eat.

The Basics of Net Carbs and Fiber

Net carbs refer to the number of grams of carbohydrates your body digests after subtracting foods like fiber.

By law, nutrition labels must list “total carbohydrates.” But knowing a product’s total carbohydrates doesn’t equate to its net carb count. That’s because if food has one or more of the following ingredients, they contribute to the total carb count:

  • Fiber
  • Sugar
  • Sugar alcohol

A person doesn’t digest all the nutrients they eat, including fiber. That’s good news for people following the keto diet; it means you can eat more carbohydrates as long as they come from high-fiber foods. 

Many—but not all—sugar alcohols also play a similar role as fiber because they pass through the body without digestion.

Number of Net Carbs Independent of Fiber To Eat on Keto

So, does fiber cancel out carbs on keto?

No, it doesn’t. Therefore, it’s crucial to determine how many net carbs are ideal for your situation to remain in ketosis. 

Most people eat between 20 to 50 grams of net carbohydrates per day, keeping in mind that the grams of carbohydrates from fiber don’t count towards these numbers. 

But every dieter has different carbohydrate needs depending on their activity level and overall energy levels as they follow the diet. 

Low Activity

According to the Centers for Disease Control and Prevention, 17.3% to 47.7% of adults are “physically inactive.” 

If you feel you have low activity levels, it’s best to ensure your net carb intake is closer to the 20-gram mark, or about 5% of your total recommended calories. Increasing your intake of fiber-rich, keto-friendly vegetables and seeds can help with this transition since you’ll be able to eat more carbs without counting as many of those carbs. 

High Activity

If you’re trying to boost your weight loss efforts by exercising regularly, your body will naturally pull from its glycogen stores for energy. In that case, you should aim to consume closer to the 50-gram net carb mark.

“High activity” is exercising three to four hours per week. But remember, we’re talking about “real” carbohydrates here. So, any grams of fiber you eat won’t count towards your relatively higher carb intake while remaining in ketosis.

Low Energy

Every person reacts to a low-carb diet differently. So, if you’re in ketosis and struggling to have enough energy to power you throughout the day, you might benefit by increasing your net carb intake to 6%.

Doing so might kick you out of ketosis and into a modified keto diet. However, since the Dietary Guidelines for Americans states that people should consume 45% to 65% of their daily calories from carbohydrates, you’ll still be well below this number.

As with the high activity group, all carbohydrates you consume from fibrous foods don’t apply to your higher net carb intake.

Simple Equation for Calculating Net Carbs

The words “net carbs” can sound intimidating. But when you’re working with packaged food, calculating net carbs is a breeze. 

The equation is as follows: Total carbs – fiber – sugar alcohols = net carbs. 

Note that all of these calculations are in grams, which is ideal, given that the keto diet counts them in the same unit. 

That said, there’s a major caveat to the equation above: Whereas fiber never increases the carb count, only certain sugar alcohols count towards a keto diet. 

The sugar alcohols that don’t contain carbs are as follows:

  • Xylitol
  • Mannitol
  • Lactitol 
  • Erythritol

These sugar alcohols don’t trigger your body to process them as carbohydrates because, like fiber, they don’t digest or absorb as easily in your body as regular sugar or other sugar alcohols. 

Equation for Calculating Sugar Alcohol

Unlike fiber, some types of sugar alcohol pass through your body after partial digestion. These count as 0.5 grams of carbohydrates per gram of sugar alcohol. 

Examples include:

  • Sorbitol
  • Isomalt
  • Maltitol
  • Glycerin

So, the equation to calculate the net carbs in a food product containing one or more of these sugars is as follows: Total carbohydrates – fiber – non-carb sugar alcohols + (carb sugar alcohol / 2) = net carbs.

Since eating excessive fiber can cause bloating and gastrointestinal discomfort, you should be aware that some sugar alcohols can also cause a similar reaction.

For example, sorbitol and maltitol are notorious for causing bloating. 

Ensuring you eat no more than 15 grams of sugar at a time may help reduce bloating discomfort. However, we recommend getting to the bottom of the problem by using elimination techniques to determine which food(s) is causing any gastrointestinal issues you might be experiencing.


If you still have questions about how carbohydrates and keto work, the answers below can help.

Can fiber knock you out of ketosis?

Fiber can’t knock you out of ketosis as long as the fiber-containing food doesn’t contain excessive amounts of digestible carbohydrates. Cucumbers and leafy greens are excellent sources of low-carb fiber, while too much fruit and legumes can take you out of ketosis.

How much fiber can you eat on keto?

Starting with 15 to 20 grams of total fiber daily is ideal for a keto diet. You can then add three to five grams at a time every few weeks until you find the right balance for you. 

Can you eat too few carbs on keto?

No, you can’t eat too few carbs on keto. The fewer carbs you eat, the easier it is to remain on this diet. Most people can consume 20 to 50 grams of carbs per day to maintain ketosis.

The Bottom Line

Calculating fiber and net carbs is critical to staying in ketosis. Unfortunately, there isn’t a standardized way for manufacturers to determine net carbs. So, some companies showcasing the net carbs on their products may use different metrics.

For this reason, if you’re having trouble staying in ketosis, it’s helpful to run your own calculations on the fiber and net carbs of any product you’re eating.