At a glance
Knowing how to calculate net carbs can be an excellent tool to increase healthy carb intake while staying in ketosis. Many ultra-processed foods have low net carbs but can still spike blood sugar, making it crucial to read nutrition labels and be able to recognize ingredients with high glycemic index scores. Food-tracking apps and continuous glucose monitors can also be helpful tools for personalized tracking and identifying foods that spike your blood sugar.
Counting net carbs is a popular strategy for those following a low-carb or ketogenic diet to increase their intake of non-starchy vegetables and healthy whole foods while still aligning with their health goals.
However, just because a meal is low in net carbs doesn’t mean it won’t spike blood sugar or insulin. Counting net carbs works best when you understand which ingredients should actually be deducted from total carbs and which could interfere with your health goals, since not all carbohydrates affect the body in the same way.
Learn how to calculate net carbs, why certain foods can spike glucose even when net carbs are low, and discover how to make meal tracking easier and more personalized to your body type.
How to calculate net carbs
Net carbs represent the grams of carbohydrate that remain after subtracting the ingredients assumed to have little or no effect on blood sugar levels. These are often called non‑impact carbs.
The usual net-carb formula subtracts dietary fiber and sugar alcohols from the grams of total carbs on the nutrition label. Some manufacturers also partially or fully deduct other ingredients—such as resistant starches and rare sugars—from their net-carb calculations.
Because “net carbs” is not an officially recognized or regulated term by the Food and Drug Administration (FDA), there is no standardized method for calculating net carbs.
Therefore, separate companies may include or exclude different ingredients in their calculations. This leads to low-net-carb products that still score high on the glycemic index, which is a measure of how quickly and intensely a food raises blood glucose levels.
As highlighted by the American Diabetes Association (ADA), relying solely on net-carb counts to support metabolic health generally isn’t recommended, as ingredients commonly excluded from net-carb counts can still affect blood glucose and insulin levels.
Watch the video below to learn about common mistakes people make when counting carbs.
Types of carbs
On a food label, all carbohydrates, including sugars, starches, fiber, and sugar alcohols, are accounted for under the category “total carbohydrates.”
Understanding the varied kinds of carbs and how they’re digested can help clarify when counting net carbs makes sense and when it may be misleading.
Here are the primary carbohydrate categories to be familiar with when tracking total carbs.
Simple carbohydrates
Simple carbs, also called fast-digesting sugars, consist of one or two sugar units, such as glucose, fructose, sucrose, or lactose.
Because of their basic structure, the body can rapidly convert them into glucose, often leading to significant blood sugar spikes, especially when they’re consumed without fiber, protein, or fat.
Common sources include table sugar, corn syrup, agave nectar, honey, fruit juice, and maple syrup.
Diets high in simple carbs, particularly from ultra-processed foods (UPFs), are associated with weight gain, higher calorie intake, and increased risk of metabolic problems, especially when they make up the majority of a person’s diet.
Complex carbohydrates
Complex carbs, which include starches and fibers, consist of long-chain sugar molecules. Their intricate structure generally takes the body longer to metabolize, typically resulting in a more gradual rise in blood sugar levels than with simple sugars.
While starches eventually break down into glucose, fiber is a non-digestible carb that the body can’t convert into glucose. Instead, fiber serves to support motility through the digestive tract and gut microbial health. There are two primary kinds of fiber: soluble fibers and insoluble fibers.
In whole foods, naturally occurring fiber and starch are naturally bound together within a food matrix. This acts as a physical barrier that slows the enzymatic breakdown of starch, resulting in more controlled glucose release.
However, when starches are refined and stripped of their natural fiber—as seen in white bread, white rice, or highly processed flours—they lose this protective buffer and can spike blood sugar nearly as rapidly as simple sugars.
Non-impact carbohydrates
Non-impact carbohydrates is a marketing term for ingredients that theoretically don’t raise blood sugar. Food companies often exclude such “non-impact” carbs from their net-carb calculations. This category can include fibers, sugar alcohols, rare sugars, and functional starches.
While some ingredients, such as erythritol and allulose, generally have little or no effect on blood glucose in most people, other ingredients marketed as “non-impact” carbs can vary widely in their effects.
For instance, research published in the Journal of Metabolic Health shows that isomalto-oligosaccharides (IMO)—often labeled as a healthy fiber—behave more like a starch than a true non‑digestible fiber, and may cause significant glucose and insulin spikes.
Other commonly used low‑impact ingredients that may still influence blood sugar include:
- Modified food starches
- Certain soluble tapioca fiber
- Maltitol
- Sorbitol
- Isomalt
- Glycerine
- Xylitol
Is counting net carbs effective for weight loss?
Counting net carbs can be a practical tool for guiding food choices, especially for those following a low-carb or Healthy Keto® diet who want to support metabolic health while still eating a variety of foods.
Tracking net carbs can help individuals feel more confident about increasing portions of healthy, whole foods that might otherwise seem too high in carbs. This can support a more balanced intake of healthy fats, proteins, and beneficial plant compounds—while still facilitating ketosis.
Calculating the net carbs of whole foods is straightforward because fiber is naturally included in the food and can be reliably deducted.
In processed foods, manufacturers often blend refined carbohydrates with large amounts of processed fibers and engineered carbohydrates, such as chicory root fiber, polydextrose, or IMOs, to make the net-carb count appear lower.
But simply adding fiber to a high-carb product doesn’t neutralize its metabolic impact, and many foods contain ingredients that can still raise blood sugar and insulin levels, which may drive cravings and make it more difficult to lose weight.
This underscores that while counting net carbs can help with more effective meal planning and support nutrient intake, low-net-carb foods—especially processed ones—are not always low-glycemic and can still potentially knock the body out of ketosis.
Helpful strategies for tracking net carbs
The best way to use net carbs is as a tool alongside other strategies, not a loophole to ignore ingredients.
Here are three ways to help you track net carbs more effectively.
Always read nutrition labels
Instead of inherently trusting products that advertise low net carbs, make a habit of always checking the nutrition facts label and ingredient list. Check the serving size, total carbohydrate, fiber, and ingredient list before deciding whether a food fits your plan.
Ingredients are listed in descending order by weight, so items near the top appear in the highest amounts per serving. If high glycemic ingredients appear on the list, especially early on, that product is probably best avoided.
Avoid processed foods
Processed foods are among the most common sources of hidden high-glycemic ingredients. Avoiding them as much as possible is one of the simplest ways to minimize your exposure to ingredients that may secretly spike blood sugar levels.
Utilize food tracking apps
Food-tracking apps can make it easier to count total carbs and run net-carb calculations.
Apps that flag ultra‑processed items or highlight added sugars and refined starches can also make it easier to spot foods that may not align with a low‑carb or Healthy Keto lifestyle, even if their net-carb amount looks appealing.
Explore your unique glucose response
“It’s not just how many carbs you eat, it’s how your body processes those carbs that determines insulin, fat burning, and energy,” explains Dr. Berg.
Research published in Nutrients shows that post-meal glucose responses depend on several personal factors beyond carbohydrate intake, including liver health, tissue insulin sensitivity, and the intestinal microbiota.
Other lifestyle factors, including stress level, sleep quality, and the order in which you eat certain foods, can further influence your glucose response to food.
To help bridge the gap, a continuous glucose monitor (CGM) can be a powerful tool for revealing your unique metabolic blueprint. The wearable sensor tracks glucose in real time, showing how your body responds after specific meals.
CGMs are especially useful for catching ingredients that fly under the radar, such as additives like maltodextrin. This additive often appears in small amounts on ingredient lists and may add almost nothing to the net-carb count, but it has a glycemic index higher than regular sugar.
Personal tracking can help you identify meals that could be slowing your progress and make food choices that naturally result in a lower blood sugar response and better support your health goals.
Key takeaways
- Net carbs generally equal total carbohydrates minus dietary fiber and selected sugar alcohols.
- Some non-impact carbohydrates commonly used in low-net-carb foods, such as certain sugar substitutes, isomalto-oligosaccharides (IMO), and soluble tapioca fibers, may still be partially absorbed and raise blood sugar in some individuals.
- Whole foods often deliver a more reliable net-carb count and provide more nutrients, including healthy fats, protein, and beneficial plant compounds, than processed foods.
- Using net carbs alongside a healthy, balanced diet, ingredient awareness, food tracking, and personal data, such as continuous glucose monitor (CGM) feedback, may be more reliable than focusing solely on the grams of net carbs you consume.
FAQ
- 1. Does fiber cancel out other carbohydrates?
- 2. Are whole grains automatically low in net carbs?
- 3. Should you subtract all sugar alcohols when calculating net carbs?
- 4. Is brown rice better than white rice when counting net carbs?
