Unless you love math, reading nutrition labels may not be your favorite aspect of following a healthy diet.
But along with calories, protein, fat, and carbs, some diets also require you to count net carbs.
Net carbs can be confusing, and not everyone needs to factor them in. However, they’re essential to understand if you follow a low-carb or keto diet.
In this article, you’ll learn precisely what net carbohydrates are, why they matter for some people but not others, and how to calculate net carbs with easy-to-follow examples.
What Are Carbs?
Carbohydrates are one of the three major macronutrients (along with protein and fats).
Technically speaking, a carbohydrate is a molecule that contains carbon, hydrogen, and oxygen atoms. The name carbohydrate comes from the fact that most carbs have a hydrogen-oxygen ratio of 2-to-1, which is the same as water.
Another term for carbohydrates is saccharides.
And there are four different types of saccharides, from smallest to largest:
- Monosaccharides
- Disaccharides
- Oligosaccharides
- Polysaccharides
Monosaccharides (also called simple sugars, such as glucose or fructose) and disaccharides (including table sugar and milk sugar) are typically referred to as sugars or simple carbohydrates.
On the other hand, complex carbohydrates like oligosaccharides (a component of some plant fibers) and polysaccharides (found in starches and some plant fibers) are distinct from sugars.
The nutritional value of carbohydrates is 4 calories per gram. A gram of protein also has 4 calories, whereas fat contains 9 calories per gram.
Another important factor of carbs is their digestion speed.
Generally speaking, carbohydrates stay in your stomach for a shorter period than protein or fats. Proteins stay longer than carbs, and fats remain the longest of all.
As a result, carbs provide your body with quick energy.
But there are also differences in the digestion and absorption of various types of carbohydrates.
Another name for the absorption rate of carbs is the glycemic index.
Carbs that raise your blood glucose quickly are called high glycemic index (GI) carbs, while carbs that absorb more slowly are called low glycemic index (GI) carbs.
The glycemic index of carbs affects the amount of energy available to your body, as well as your health.
Over time, eating too much sugar can lead to insulin resistance, which is associated with coronary heart disease and other chronic diseases[*].
But unlike sugars, low-GI or “slow” carbs raise your blood sugar gradually. As a result, they’re probably a better choice for your health[*].
What Are Net Carbs?
Net carbohydrates are any carbohydrates that your body can digest and convert into glucose.
Other names for net carbs include real carbs, impact carbs, effective carbs, or digestible carbs.
The basic idea behind net carbs is that some carbohydrates count towards your daily total, while others don’t.
All simple carbs count towards your net carbs. And most complex carbs do, too, with one exception: fiber.
Fiber: The Difference Between Carbs and Net Carbs
Fiber is a type of complex carb from plants that contributes little or no energy to your body.
Because fiber has a carbohydrate structure, it’s still considered a carb, but because your body can’t break it down into glucose, it’s not a net carb.
There are two types of fiber: soluble fiber and insoluble fiber.
Soluble fiber occurs primarily in fruits and vegetables. And in water, it forms a gel-like solution, which is where the name "soluble fiber" comes from.
Also, soluble fiber increases your sensation of fullness after eating. Some research suggests that eating more soluble fiber may lead to weight loss by reducing your appetite[*].
Additionally, soluble fiber can also act as a prebiotic, feeding your gut bacteria and promoting a healthy microbiome[*].
In contrast, insoluble fiber mainly occurs in legumes and whole grains (and in a few vegetables like cauliflower and green beans).
And unlike soluble fiber, insoluble fiber doesn’t dissolve in water.
Insoluble fiber also increases the speed at which food moves through your gastrointestinal tract, and it adds bulk to your stool[*]. Some people use insoluble fiber to aid their bowel movements.
Additionally, soluble fiber reduces the glycemic index (absorption time) of other carbs, whereas insoluble fiber does not[*].
Fiber is good for you and doesn't count towards net carbs, so there's no reason to avoid it…right?
Unfortunately, you do need to watch for "fake fiber." Some food manufacturers mislabel a type of ingredient called isomaltooligosaccharides (IMOs for short) as fiber.
Unlike real fiber, IMOs are a short-chain carbohydrate that does raise your blood sugar[*].
Here are some ingredient names under which food makers hide IMOs:
- Vegetable Fiber
- Prebiotic Fiber
- Soluble Corn Fiber
- Tapioca Fiber
- Soluble Tapioca Fiber
Although the FDA recently ruled companies can’t label IMOs as fiber, you should still look out for manufacturers sneaking them in, especially if you follow a low-carb or keto lifestyle[*].
Sugar Alcohols and Net Carbohydrates
Sugar alcohols are organic compounds derived from carbohydrates, with an alcohol structure.
Most sugar alcohols are polyols, meaning they have multiple hydroxyl (-OH) groups attached to them — unlike ethanol (drinking alcohol), which only has one.
Here are some common examples:
- Erythritol
- Xylitol
- Mannitol
- Sorbitol
- Maltitol
- Isomalt
The primary purpose of sugar alcohols is as a sweetener in foods, beverages, and products like chewing gum.
But do sugar alcohols count as net carbs?
First of all, your body can’t digest all the calories in sugar alcohol[*].
That’s why some experts recommend counting half the net carb content of sugar alcohol compared to regular carbs[*].
Confused? Don’t worry, we’ll revisit sugar alcohols in a moment, with practical examples of how they affect your net carb count.
For now, just keep in mind that sugar alcohols (often found in sugar-free foods) do contain digestible calories, and they can affect your blood glucose and insulin levels.
Low Carb and Keto Diets: When Net Carbs Matter the Most
Unless you’re a nutrition nerd, you may not be thrilled at the idea of tracking your net carbs.
However, if you follow a low-carb or ketogenic diet, it’s definitely a good idea.
The scientifically-supported idea behind low-carb, high-fat (LCHF) diets like keto is this: when you limit your carb intake, your body burns more fat and your insulin sensitivity increases[*][*].
While there’s no official definition for a low-carb diet, at Levels we like to define low-carb as 100 grams or less of net carbs per day.
And in the case of keto in particular, limiting carbs is essential to reach and sustain the state of ketosis. If you eat too many carbs, your body won’t produce endogenous ketones, which goes against the entire purpose of the ketogenic diet.
For most people, limiting daily intake to 30 grams or less of net carbs is necessary to sustain ketosis.
However, whether you eat keto or another LCHF diet, fiber is allowed — and it’s also good for you.
Therefore, you’ll want to focus on limiting net carbs (digestible carbs), not total carbs (which include non-digestible fiber).
Lastly, people with diabetes can also benefit from counting net carbs. The reason is because net carbs (as opposed to total carbs) have a stronger influence on your blood glucose levels.
Also, research shows that going low-carb or keto can help people with diabetes control their blood sugar as well as improve insulin sensitivity[*][*][*].
However, if you have diabetes or take blood sugar medication, make sure to speak to a qualified doctor before you change your diet.
How to Calculate Net Carbs
Now you know why you might want to calculate net carbs. Here’s how to do it.
Remember: net carbs are the carbs remaining in food after you subtract non-digestible carbs.
Here’s the basic formula:
Total Carbs - Fiber = Net Carbs
For our first example, imagine that you’re eating a normal-sized apple.
Many whole foods have fiber as well as net carbs, including apples.
The apple has 14 grams of total carbs and 3 grams of fiber. Therefore, to get net carbs, we subtract fiber from total carbs:
14g - 3g = 11 grams of net carbs
That wasn’t so hard, was it?
However, some foods have more fiber than net carbs. For another example, let’s consider avocados, a keto diet staple.
A pitted avocado that weighs 200 grams has about 17 grams of total carbs and a whopping 13 grams of dietary fiber:
17g - 13g = 4 grams of net carbs
With so much fiber and low net carbs (not to mention lots of healthy fats), it’s no wonder that avocados are well-suited to the keto diet.
Essentially, as long as you can either look at a nutrition label or look up the nutrition facts for your food, you can always calculate net carbs using basic subtraction.
However, sugar alcohols make things just a bit harder.
Remember how we discussed earlier that some experts recommend counting half the net carbs for sugar alcohols?
Here’s the formula if a food has sugar alcohols:
Total Carbs - Fiber - (Grams of Sugar Alcohol ÷ 2) = Net Carbs
Now, let’s imagine you’re considering whether to buy a “low-carb” protein bar at your local health food store.
The bar has 50 grams of total carbs, including 10 grams of fiber and 30 grams of sugar alcohol:
50g - 10g - (30g ÷ 2) = 25 grams of net carbs
As you can see, your decision to buy the bar depends on your daily net carb allowance.
If you’re following LCHF with up to 100 grams of carbs allotted per day, the product is acceptable. But if you’re trying to stay in ketosis by eating 30 grams of carbs or less per day, you should probably pass.
The Takeaway
Depending on your diet of choice, you may not need to distinguish between total carbs and net carbs.
But if you follow a low-carb or keto diet, tracking your net carb intake is worth your time.
Remember the difference between total carbs, fiber, and sugar alcohols, and don’t forget the formula:
Total Carbs - Fiber - (Grams of Sugar Alcohol ÷ 2) = Net Carbs
And regardless of your diet and goals, minimizing your sugar intake and focusing on whole foods with plenty of fiber is an excellent way to ensure you stay healthy for life.
