When it comes to low carbohydrate or ketogenic diets, opinions on carbs differ greatly. 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.

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

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 carbohydrates that can be absorbed by the body. These include both simple and complex carbohydrates. Simple carbohydrates contain one or two sugar units linked together (think fruits, vegetables, milk and honey). Complex carbohydrates contain many sugar units linked together (as in potatoes, rice and bread).

Certain 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

Fiber

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

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.

The type of fiber, insoluble or soluble will determine what happens once it has reached the large intestine.

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.

Soluble fiber dissolves in water forming viscous gels that bypass the small intestine where fermentation occurs in the large intestine. 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.

Fermentation of 1 gram of soluble fiber to SCFAs including acetate, butyrate and propionate, can provide between 1—2 kcal. Although soluble fiber does produce energy, it has shown no direct effect on blood sugar levels, with studies showing that it can improve glucose sensitivity in the body. The production of the SCFAs have also been shown to have specific benefits including improving insulin sensitivity, decreasing blood glucose and reducing inflammation.

Isomaltooligosaccharides (IMOs)

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. Recent research has shown that IMOs are partially absorbed into the small intestine, acting more like non-fiber carbohydrates.

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.  Check any low-carb or “sugar-free” bars to ensure they have not been sweetened with this ingredient.

Fiber and 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 been shown to effect satiety through several physiological mechanisms throughout the digestive tract.

Soluble fiber itself, when fermented in the large intestine produces hormones including glucagon-like peptide (GLP-1) and Peptide YY (PYY). Both of these hormones can contribute to feelings of fullness. Studies have also linked the ingestion of fiber with decreasing energy intake over time 

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.

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 affect how the body responds to them. Most polyols are fermented in the large intestine by the gut microflora; however, some are partially absorbed in the small intestine. Some unabsorbed sugar polyols such as erythritol are excreted in the urine.

Many manufacturers have been turning to sugar alcohols as a substitute to sugar. Polyols have a lower nutritional value than sugar but with a similar sweetness. They can therefore be used 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. However, those with diabetes and prediabetes have noted an impact with the intake of malitol on their blood sugar levels.

Another well-known side effect of sugar alcohols are gastrointestinal upsets such as bloating, gas and diarrhea.

The Problem with Net Carbs

Many manufacturers of low carbohydrate products have seen the potential in using sugar alcohols. 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 number 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 the plethora of 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 that the whole concept of net carbs should be avoided.

However, there is a huge difference 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).

Counting Carbs

Should you then count net carbs or total carbs?

The simple answer depends on your overall goals for following a low carbohydrate diet.

Therapeutic Reasons

For individuals who are following a low carbohydrate or ketogenic diet for therapeutic reasons including those with epilepsy, Parkinson's Disease and Alzheimer's disease counting total carbohydrates will be of utmost importance. Even the slightest increase in blood sugar or insulin levels can directly affect disease management.

Weight Loss

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

Advantages of Counting Net Carbs

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.

Less Restrictive

One major reason why people fail on a low carbohydrate diet is that they find it 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.

Balance Blood Sugar Levels

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

Quality Matters

When it comes 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 consuming a large number of processed or mass-produced "low carbohydrate" foods, this could be creating challenges including stalled weight loss, blood sugar fluctuations and an increase in inflammatory markers. Processed and manufactured products will often contain a myriad of other compounds, all of which can affect the body in very negative and different ways.

Similarly, 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 in turn significantly affecting the health of your body and your wellness goals.

In Conclusion

No matter what dietary choices you choose to follow, it is important they fit in with your lifestyle. If counting total carbohydrates works for you and the health of your body then continue to follow this approach.

Counting net carbs can offer several benefits to you and your goals in the long-term. It may be a better approach for weight loss, it is definitely far less restrictive and can help balance blood sugar levels.

With having many sugar-free products available 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.

The real question you should be asking yourself is whether the foods you're eating are from whole food sources as opposed to "low-carb" products. If you are counting net carbs, make sure you check the label for blood sugar spiking ingredients.