When Counting Macros Do I Subtract Fiber From Carbs?

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OK, so when I was new to low carb/ keto dieting I had no idea what net carbs were and why I needed to know about them. As I became more aware of my carbohydrate intake I noticed some nutrition labels. I became a label reader. I knew the difference between Carbs, Fats, and Protein.

Today they are referred to as your macronutrients. On a keto or low carb diet, you need to balance your macronutrients. Instead of counting calories per se, you are concentrating more on the number of grams you are eating and the percentage of each macronutrient.

I started to be more carb aware because you are very limited in carbohydrates on a low carb keto diet.

Usually, there is more on the nutrition label then just total carbohydrates in grams.

I started paying attention to fiber, sugar, and sugar alcohols as well. Sometimes they are all listed under carbs. You need to know this so you don’t go over your carbohydrate limit per day since carbs are part of the macronutrients you pay attention to on any diet and especially on a keto diet.

Generally, on a low carb/keto diet you divide your food consumption up between 5% Carbohydrates, 70% fats, and 25% protein. There are macro calculators online free to help you.

Any time you consume less than 50 grams of carbohydrates per day you can cause your body to switch from being a glucose (sugar/ carb)  burner to a fat burner. It takes a few days of cutting down your carbs to get into ketosis. Ketosis is the state where your body switches from a glucose burner to a fat burner and your body starts to put out ketones.

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Getting 5% carbohydrates on a keto diet amounts to eating 20-50 grams of carbs a day depending on your body and weight loss goals.  The good thing is if there is fiber listed under the carbohydrates you can essentially subtract that from the total carbs and not count the fiber because your body does not absorb fiber.

On a low carb diet you need to get your energy from fat and protein but not so much protein that it kicks you out of ketosis. Ketones will build up in your body when you eat less sugar because your body is not using glucose (sugar) as a source of energy. It is using stored fat and ketones.

Manufacturers came up with the term “Net Carbs” in the 2000s but there is no “official definition” of net carbs so it can be deceiving. If you go on a keto diet and count your carbs every carb counts. Net carbs are the carbs you can actually use like starches and sugar that turns into glucose and your body absorbs and uses for energy.

There are other carbohydrates that have little energy value and don’t impact your blood sugar. You don’t count them therefore in your daily carbohydrate limit. The ones you don’t count or hardly count are fiber and sugar alcohols.

To Calculate Net Carbs you take the total carbs and subtract (1) fiber, which your body can not process because we do not have the same enzymes to break it down like a cow, for example, who eats grass. So for humans fiber has zero carbs and zero calories.

And (2) sugar alcohol like xylitol and erythritol. Sugar alcohols are similar to sugar,  but have a chemical difference that makes them totally or partially indigestible. They taste sweet so you find these in artificial sweeteners. However not all sugar alcohols act this way and some do impact your blood sugar levels and should be calculated.

Sugar Alcohol you don’t count
  • Erythritol
  • Xylitol
  • Mannitol
  • Lactitol
Sugar alcohol you do count
(each gram is counted for ½)
  • Maltitol
  • Sorbitol
  • Isomalt
  • Glycerine

Each gram of Maltitol, Sorbitol, Isomalt, and Glycerine is divided by 2 and added to your total carb gram count per day.

The Net Carbohydrate formula:

Grams Carbs – fiber + Maltitol/2 or any of the sugar alcohols that do count. A note about sugar alcohols, your gut bacteria can ferment sugar alcohol and cause bloating and gas so you should not consume too much of it..

Fiber does not trigger your insulin to rise in your blood levels. Fiber is a big help to your system when it comes to elimination, as in going to the bathroom regularly. If you do not consume enough fiber you may have digestive problems.

If you have just started a low carb keto diet you may have constipation and need to add fiber to your diet. Most people get back on track after a few weeks after your body adjusts to switching to a low carb diet.

Your gut flora (microbiome)  can also be affected so some people have found it beneficial to feed your gut flora, prebiotic fiber as in onions, garlic, asparagus, and leeks.

Adding bulk to your stool to help constipation may be aided by eating the following keto-friendly veggies:

  • Cabbage
  • Cauliflower
  • Green beans
  • Lettuce
  • Cucumber
  • Kale
  • Peppers
  • Spinach
  • Avocado
  • Eggplant
  • Broccoli

Fibrous foods like sweet potatoes, legumes, beans, and starchy veggies have fiber but are too high in carbs to include on a keto-friendly list. Some keto dieters add flaxseed, chia seeds, coconut, psyllium husk to add fiber but you may have to add any carbs that are not fiber to your total carbohydrate count.

I found these flax wraps that I make on my keto diet because flax seeds have lots of fiber and little carbs. They also have protein and fat. Flaxseed wraps have 4 ingredients and each wrap has only 1.2 grams of net carbs. I like to add a bit of salt to the recipe because initially, you may lose sodium on a keto diet.


Each wrap contains 26grams of fat per wrap coming from omega 3 fatty acids,  11.6 grams of protein, with 17grams of fiber and only 1.2grams of carbs. The trick to these wraps is making sure the flour is very fine and uses boiling water not cold water to form the dough. I roll my dough between two pieces of baking paper.

Enjoy subtracting fiber from your carbohydrate gram calculations and keep up the good work. Its not so hard once you get the hang of it all.

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