Should I Count Net Carbs? Separating Facts from Opinions

The question to count total or net carbs remains a topic of debate within the low carb community.

Many people believe that avoiding all carbohydrates is the optimal approach, whilst others think the inclusion of some fibrous carbohydrates can actually help achieve their goals.

This article will explore exactly what is meant by "net carbs" and the best approach to achieve your goals on a low carbohydrate diet.

What is a Net Carb?

Nutrition guidelines still do not officially recognize the concept of a "net carb". This means that the way to determine how many net carbs are contained in a food can be confusing.

Net carbs, also known as digestible carbohydrates, is a term given to those that can be absorbed by the body. These carbs include both simple and complex carbohydrates. Simple carbs contain one or two sugar units linked together e.g. fruits, vegetables, milk and honey. Complex carbs contain many sugar units linked together e.g. potatoes, rice and bread.

However, some carbohydrates cannot be broken down at all, with others only being partially broken down and absorbed — these are primarily fiber and sugar alcohols. The calculation for working out net carbohydrates becomes:

Total Carbs – Fiber and Sugar Alcohols = Net Carbs

Is Fiber the Same as Sugar?

Many people attempting to avoid or count total carbohydrates often put fiber in the same category as simple sugars. Meaning they believe that consuming fiber will have the same impact on blood glucose and insulin levels as that of sugar.

However, the way the body processes fiber is uniquely different to other carbohydrates. Unlike simple carbohydrates, fiber bypasses absorption in the small intestine, passing directly into the large colon (1Trusted sourceOxford AcademicA department of the University of Oxford, Oxford University Press publishes the highest quality scientific journals.Open link).

What happens to this fiber once in the large intestine depends on the type of fiber, of which there are two — insoluble and soluble.

What is the Difference Between Insoluble and Soluble Fiber?

Insoluble fiber does not dissolve in water and passes through the colon unabsorbed — this type of fiber can help with constipation and has no effect on blood sugar or insulin levels (2Trusted sourceNational Center for Biotechnology InformationNCBI's mission is to develop new information technologies to aid in the understanding of fundamental molecular and genetic processes that control health and disease.Open link).

Soluble fibers instead dissolves in water forming viscous gels that bypass the small intestine where fermentation occurs in the large intestine (2Trusted sourceNational Center for Biotechnology InformationNCBI's mission is to develop new information technologies to aid in the understanding of fundamental molecular and genetic processes that control health and disease.Open link). Once inside the colon, fermentation of the fiber occurs producing short chain fatty acids (SCFAs). SCFAs act as substrates for the microbiota, providing a source of energy and improvements to the intestinal environment (3Trusted sourceNational Center for Biotechnology InformationNCBI's mission is to develop new information technologies to aid in the understanding of fundamental molecular and genetic processes that control health and disease.Open link).

Fermentation of 1 gram of soluble fiber to SCFAs including acetate, butyrate and propionate, can provide between 1—2 kcal (4Trusted sourceNational Center for Biotechnology InformationNCBI's mission is to develop new information technologies to aid in the understanding of fundamental molecular and genetic processes that control health and disease.Open link, 5Trusted sourceOxford AcademicA department of the University of Oxford, Oxford University Press publishes the highest quality scientific journals.Open link). Although soluble fiber does produce energy, it has shown no direct effect on blood sugar levels, with studies showing that it can in fact improve glucose sensitivity in the body (6Trusted sourceOxford AcademicA department of the University of Oxford, Oxford University Press publishes the highest quality scientific journals.Open link). Furthermore, the production of the SCFAs have shown to have specific benefits including improving insulin sensitivity, decreasing blood glucose and reducing inflammation (7Trusted sourceNational Center for Biotechnology InformationNCBI's mission is to develop new information technologies to aid in the understanding of fundamental molecular and genetic processes that control health and disease.Open link).

Are IMOs a Fiber?

A newer form of fiber that has gained in popularity in the food and supplement industry are isomaltooligosaccharides (IMOs).

In 2018 the FDA classed IMOs as a form of fiber because they were believed to be resistant to certain digestive enzymes. However, recent research has shown that IMOs are partially absorbed into the small intestine, acting more like non-fiber carbohydrates (8Trusted sourceResearchGateResearchGate is the professional network for scientists and researchers aiming to connect the world of science and make research open to all.Open link).

This digestive impact could result in IMOs having a significant effect on blood sugar and insulin levels. For this reason, the FDA has now de-listed IMOs as being a form of fiber — be sure to check any low-carb or “sugar-free” bars haven’t been sweetened with this ingredient.

Products with isomaltooligosaccharides (IMOs) may spike your blood sugar and insulin levels. Be sure to avoid products that use IMOs if you follow a low-carb or keto diet.

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How Does Fiber Affect Weight Loss?

Research has been conducted to evaluate the effect of fiber and body weight, most of which demonstrate an inverse relationship between dietary fiber and a decrease in body weight.

Certain types of fibers have shown to effect satiety through several physiological mechanisms throughout the digestive tract (9).

Soluble fiber itself, when fermented in the large intestine produces hormones including glucagon-like peptide (GLP-1) and Peptide YY (PYY) (2Trusted sourceNational Center for Biotechnology InformationNCBI's mission is to develop new information technologies to aid in the understanding of fundamental molecular and genetic processes that control health and disease.Open link). Both of these hormones can also contribute to feelings of fullness.

Studies have also linked the ingestion of fiber with decreasing energy intake over time (2Trusted sourceNational Center for Biotechnology InformationNCBI's mission is to develop new information technologies to aid in the understanding of fundamental molecular and genetic processes that control health and disease.Open link). A study consisting of 252 middle aged women observed an average of 4.4 lbs loss over a 20 month period due to an 8 gram increase in fiber per 1,000 kcal (10Trusted sourceOxford AcademicA department of the University of Oxford, Oxford University Press publishes the highest quality scientific journals.Open link).

Although increasing dietary fiber has been linked to the benefits of losing or maintaining weight loss, more research is needed to determine the optimal types of fiber to ingest.

Eat a whole foods based low-carb diet and minimize the consumption of "keto" products. Whole foods contain a significantly higher amount of fiber and no sugar alcohols or other potentially blood sugar spiking ingredients.

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If your weight is stalling on a keto diet, here are some resources that may help:

• How To Low Carb 15+ Common Weight Loss Mistakes
• How to Stay Motivated During a Weight Loss Stall

What is the Effect of Sugar Alcohols?

The other non-digestible forms of carbohydrates include sugar alcohols, also known as polyols. The most common forms include erythritol, isomalt, malitol, sorbitol and xylitol.

Although they are processed similarly to fiber, key differences affects how the body responds to them. The majority of all polyols undergo fermentation in the large intestine by the gut microflora; however, some are partially absorbed in the small intestine (11Trusted sourceSpringer LinkSpringer Link offers peer-reviewed research from the world's most trusted sources.Open link). Likewise, unlike fiber, some unabsorbed sugar polyols such as erythritol are excreted in the urine (11Trusted sourceSpringer LinkSpringer Link offers peer-reviewed research from the world's most trusted sources.Open link).

Similarly, many manufacturers have been turning to sugar alcohols as a substitute to that of sugar. Polyols have a lower nutritional value than sugar but with a similar sweetness. Therefore, manufacturers use them, volume-for-volume, to replace sugar and are often termed bulk sweeteners.

Due to having a low glycemic index (GI) in relation to sugar, sugar alcohols cause low or no increase in blood glucose or insulin secretion (11Trusted sourceSpringer LinkSpringer Link offers peer-reviewed research from the world's most trusted sources.Open link). However, those with diabetes and prediabetes have noted an impact with the intake of malitol on their blood sugar levels (12).

Another well-known side effect of sugar alcohols include gastrointestinal upsets such as bloating, gas and diarrhea (13Trusted sourceNational Center for Biotechnology InformationNCBI's mission is to develop new information technologies to aid in the understanding of fundamental molecular and genetic processes that control health and disease.Open link).

Bottom line: Not all sugar alcohols are equal. Some may raise your blood sugar and insulin levels and some may also cause GI distress.

Why Do Net Carbs Have a Bad Name?

Many manufacturers of low carbohydrate foodstuffs have seen the potential in using sugar alcohols in their products. As such, there is an array of foods available claiming to be "low in carbohydrates" or "low in net carbs" because they contain a large amount of polyols.

While certain sugar alcohols like erythritol have little to no effect on blood sugar, other frequently used sweeteners like maltitol, sorbitol and isomaltooligosaccharides (IMOs) have a more significant impact on blood sugar levels and contain more calories. However, when labeled, such sweeteners are often fully deducted from the total carb count resulting in seemingly low net carbs.

With having many sugar-free products available (where all of the sweeteners will be substituted with polyols) that are being marketed as low in net carbs; it can give the perception to anyone following a low carbohydrate diet that the whole concept of net carbs should be avoided.

However, a huge difference exists in the quality of a product that is real food based vs a product that has been mass-produced, especially in the net carbs that it contains.

For example, the net carbs that are contained within some nuts or an avocado are very different to those contained in a low carbohydrate nut bar. This is because the real, whole foods will contain a significantly higher amount of fiber and no sugar alcohols. Whereas the processed foods will be lower in net carbs, primarily due to containing polyols and little to no fiber (depending on the product).

For more information about low-carb sweeteners, check out these posts:

• Top 5 Keto Sweeteners and Low-Carb Sweetener Conversion Chart
• Can I Have Allulose on a Healthy Low-Carb Diet?
• Can I Have Tagatose on a Healthy Low-Carb Diet?

Sweeteners like maltitol, sorbitol and IMOs may spike your blood sugar levels. When labeled, such sweeteners are often fully deducted from the total carb count resulting in seemingly low net carbs.

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Should I Count Net Carbs or Total Carbs?

The simple answer to this question is — it depends on your overall goals for following a low carbohydrate diet.

Count Total Carbs for Therapeutic Reasons

For individuals who are following a low carbohydrate or ketogenic diet for therapeutic reasons e.g. those with epilepsy, Parkinson's Disease and Alzheimer's disease counting total carbohydrates will be of upmost importance. This is because even the slightest increase in blood sugar or insulin levels can directly affect disease management (for more information on the types of ketogenic diets, head to this previous post).

Count Net Carbs for Weight Loss

For individuals with a weight loss or general health goal, counting net carbs over total carbs could actually be of benefit.

Three Advantages of Counting Net Carbs

1. It May Promote More Weight Loss

Having foods which are higher in fiber will improve the gut flora, may promote more satiety and result in an overall reduction in food intake; all of which has a positive impact on weight loss.

2. It is Less Restrictive

One major reason why people fail on a low carbohydrate diet is that it is too restrictive. When you under-take any changes in dietary habits, they should be something that can fit into your lifestyle. If you view this just as a ‘diet’ and something to follow in the short term, you undoubtedly will fall off the wagon, affecting any positive changes. If you follow a total carbohydrate diet this can even limit foods such as berries or certain vegetables.

3. It Can Help Balance Blood Sugar Levels

Managing healthy blood sugar levels becomes particularly important for individuals with hypoglycemia issues or those injecting insulin.

As long as you follow a whole foods based diet, counting net carbs offers several benefits; it may be a better approach for weight loss, it's less restrictive and can help balance blood sugar levels.

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Rather Than Net Carbs Focus on Quality Food Sources

When it comes down to whether you should count net carbs or not, the real question you should be asking yourself is "are the foods I’m eating from real, whole food sources?"

For the vast majority of individuals, it really does not matter whether you are counting total or net carbohydrates, as long as you are consuming real, whole foods.

If you are however consuming a large number of processed or mass-produced "low carbohydrate" foods — then this could be causing issues such as a stall in weight loss, blood sugar fluctuations and an increase in inflammatory markers. This is because these products will often contain a plethora of other compounds within in them, all of which can affect the body in very negative and different ways.

Likewise, consuming a large amount of low carbohydrate foods with sugar alcohols in them can cause significant gastrointestinal upsets. Whilst this can happen in the short term, long-term ingestion of sugar alcohols can also disrupt the good bacteria in the gut — significantly affecting the health of the body and goals such as weight loss.