Net Carbs

What Are Net Carbs?

Net carbs is an informal nutritional concept used primarily in low-carbohydrate and ketogenic diet contexts. It refers to the carbohydrates that are believed to significantly raise blood glucose and therefore "count" toward a daily carbohydrate limit. The most common calculation is:

Net Carbs = Total Carbohydrates − Dietary Fiber − Sugar Alcohols (partially)

The rationale is that dietary fiber is not digested or absorbed in the small intestine (and thus does not raise blood glucose), and most sugar alcohols have a minimal glycemic effect. However, it is important to note that "net carbs" is not a regulated or standardized term by the FDA or most major health organizations.

Limitations and Caveats

The net carb concept has several important nuances that affect its reliability:

• Soluble fiber: some soluble fibers are fermented by gut bacteria and yield approximately 2 kcal/g; highly fermentable fibers may have a modest glycemic effect in some individuals
• Sugar alcohol variability: not all sugar alcohols are equal. Erythritol has nearly zero glycemic effect, while maltitol has a glycemic index of about 35 — roughly half that of glucose. Blanket subtraction of all sugar alcohols can significantly underestimate the glycemic impact of some products
• Individual response: blood glucose response to any carbohydrate source varies by individual based on gut microbiome composition, insulin sensitivity, and food matrix effects
• Label accuracy: food manufacturers sometimes market products with aggressively low "net carb" claims that may not reflect true metabolic impact

Practical Use

For individuals following a standard diet, tracking total carbohydrates and dietary fiber separately is generally more accurate than relying on net carbs. For those on ketogenic diets (typically targeting less than 20–50 g of net carbs per day), net carbs can serve as a practical tracking tool, provided fiber is subtracted but sugar alcohols other than erythritol are subtracted only at 50% or less of their listed gram value.

• Example A: A product with 25 g total carbs, 10 g fiber, and 5 g erythritol has approximately 15 g net carbs (25 − 10 − 5 = 15)
• Example B: A product with 25 g total carbs, 3 g fiber, and 10 g maltitol has approximately 17 g net carbs (25 − 3 − 5 = 17, using 50% of maltitol), not 12 g as a full subtraction would suggest