What Are Net Carbs and How to Calculate Them

what are net carbs

Food manufacturers coined the term ‘net carbs’ during the low-carb craze of the past decade, in an attempt to further bolster the hype. It ensures dieters that they can eat sweet and salty foods without the need to count their actual carbohydrate load. The term, however, is not officially recognized by nutrition experts. There is no legal definition, so the Nutrition Facts labels of foods bearing it are not regulated by the Food & Drugs Administration.                                        

To date, whether to count totals carbs or net carbs remains a controversial topic, and because of outdated and conflicting information, determining how to compute net carbs can be quite confusing. Moreover, the net carbs labels on packed foods are not necessarily indicative of the number of carbs that your body really absorbs.

Fortunately, understanding how your body processes the various types of carbohydrates may help in attaining your target blood sugar level and weight loss goals. In this article, we will take a close look at the science behind net carbs and learn how to calculate them based on your food intake.

What Are Net Carbs?

Also known as digestible or impact carbs, net carbs refer to the carbohydrates absorbed by your body, including both simple and complex carbs. Whenever you eat food stuffs containing carbohydrates, most of the carbs are broken down in the small intestine into individual sugar units. The rationale behind this is that only individual sugar units can be absorbed by your body.

However, some carbohydrates cannot be broken down into individual sugars, while others are only partially broken down. These include dietary fiber and sugar alcohols, both of which can be deducted from total carbs when computing for net carbs.

How Your Body Processes Fiber

Fiber is a special type of carbohydrate with regard to its digestion and physiologic effects. Unlike sugar and starch, naturally occurring fiber is not absorbed in your small intestine because enzymes cannot break the bond between the sugar units. Consequently, fiber passes directly into your colon. Its fate after that relies on what kind of fiber it is.

There are two classes of fiber: soluble and insoluble. Roughly two-thirds of the fiber in your diet is insoluble, while the rest is soluble. Insoluble fiber leaves your colon unchanged, provides no calories and does not have any effect on blood sugar or insulin levels. In contrast, soluble fiber creates a gel that slows down the movement of food through your system and can make you feel full. When soluble fibers reach your colon they are fermented by bacteria into short-chain fatty acids (SCFAs). These SCFAs help in keeping your gut healthy and provides several other health benefits.

Note that soluble fiber does not appear to increase blood glucose. As a matter of fact, recent scientific studies suggest that its effects in the gastrointestinal tract help reduce blood sugar levels. Multiple studies have also demonstrated that soluble fiber may lead to increased insulin sensitivity, better blood sugar control, and absorption of fewer calories.

How Your Body Processes Sugar Alcohol

Sugar alcohols are processed by your body just like it handles fiber, with some significant differences. A lot of sugar alcohols are only absorbed partially in the small intestine, and there are a lot of differences among various types.

According to researchers, 2 to 90% of sugar alcohols are absorbed by the small intestine. However, some are only absorbed briefly into the bloodstream and later excreted in urine. Moreover, these sugar alcohols can have different effects on blood glucose and insulin levels.

Below is a list of the insulin and glycemic indexes for the most common sugar alcohols. For comparison purposes, note that the insulin and glycemic index of glucose are both 100.

  • Maltitol: Insulin index 27 / Glycemic index 35
  • Xylitol: Insulin index 11 / Glycemic index 13
  • Sorbitol: Insulin index 11 / Glycemic index 9
  • Isomalt: Insulin index 6 / Glycemic index 9
  • Erythritol: Insulin index 2 / Glycemic index 0

By far the most commonly used sugar alcohol in processed food is maltitol. It is partially absorbed in your small intestine, while the rest is fermented by bacteria in your colon. Studies have also shown that it contributes 3-3.5 calories per gram, as compared to sugar which contributes 4 calories per gram. Maltitol has likewise been reported to increase blood sugar levels in diabetics.

In terms of net carbs, the best all around choice appears to be erythritol. Roughly 90% of it is absorbed in your small intestine and later excreted in urine. The remaining 10% is fermented to short-chain fatty acids in the colon, making it carb-free, calorie-free and unlikely to trigger digestive problems.

Studies have revealed that other sugar alcohols are also partially absorbed and can raise blood sugar, but to a lesser degree than maltitol. However, they appear to cause bloating and loose stools in a lot of people.

On the whole, it seems that sugar alcohols don’t have a considerable effect on blood sugar and insulin levels, although individual responses may differ, particularly among diabetics.

How to Calculate Net Carbs in Whole Foods

Naturally occurring fiber can be found in whole food. Hence, you can just subtract the fiber from the total carbs to determine the net carbs. For instance, an avocado contains 9 grams of total carbs, of which 7 grams are fiber.

So, 9 grams of total carbs – 7 grams of fiber = 2 grams of net carbs.

How to Calculate Net Carbs in Processed Food

1) Net Carbs from Fiber

You can completely subtract most fibers from the total carbs displayed in the nutrition label. If you’re living outside the United States, note that the fiber has already been removed from the total carbohydrate line and is listed separately. However, if isomaltooligosaccharide (IMO) is included in the ingredients list, you only need to subtract half of the fiber carbs.

2) Net Carbs From Sugar Alcohols

In general, you can subtract 50% of the carbs from sugar alcohols from the total carbs listed on the nutrition label. An exception is erythritol. In case it is the only sugar alcohol in the ingredients list, you can completely subtract its carbs from the total carbs.

The value that you’ll get may be different from the number of net carbs shown on the product label because many companies calculate net carbs by subtracting all fiber and sugar alcohol carbs.

The Pros

  • Less Restrictive – by calculating net carbs you’ll be able to widen your food choices.
  • Promotes Higher Fiber Intake – Foods rich in fiber promote fullness, reduce blood sugar and calorie absorption.
  • Lessens Risk of Hypoglycemia in Insulin Users – people taking insulin in order to cover all carbs without making necessary adjustments for high-fiber and erythritol-containing foods may experience a drop in blood sugar.

The Cons

  • Not 100 Percent Accurate – so far, it is not possible to calculate net carbs with pinpoint precision because of the varying effects of processing fiber, individual responses, and the mixture of sugar alcohols used in food products.
  • May Not Be Effective For Some With Type 1 Diabetes – although subtracting fiber carbs may help prevent hypoglycemia in some people with type 1 diabetes, others claim that calculating all carbs makes it easier for them to regulate blood sugar.
  • Can Lead To Increased Intake Of Sugar-Free Treats Excessive consumption of food labeled as “low in net carbs” may impede weight loss, increase blood sugar and cause other health issues.

At the end of the day, the decision on whether to calculate total or net carbs must be based on what really works best for you.


The debate as to whether it is more precise to calculate total or net carbs won’t end anytime soon. However, knowing how your body processes different types of carbohydrates can help in regulating your blood sugar, weight and overall fitness level.

Counting net carbs is one way to achieve this. Net carbs basically pertains to carbohydrates that are absorbed by your body. In order to calculate the net carbs in whole foods, simply subtract the fiber from the total number of carbs. For processed foods, subtract the fiber and a portion of the sugar alcohols.

Nonetheless, bear in mind that the “net carbs” shown on food labels can be misleading, and individual responses vary. In case you find that calculating net carbs results in higher than expected blood sugar levels, you may shift to counting total carbs instead.

The most important thing is to ingest the number of carbs that enables you to achieve your fitness goals, regardless of how you calculate them.

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