Net Carbs (Keto)

Net carbs: what really counts in a keto diet

Net carbs = total carbohydrate − fiber − (part of the sugar alcohols/polyols). Why subtract those? Fiber doesn't raise blood glucose, since the small intestine doesn't absorb it, and most polyols (erythritol, xylitol, maltitol) are absorbed slowly or not at all. Example: a label showing 30 g of total carb, 8 g of fiber and 0 g of polyols leaves you with 22 g of net carbs per serving. A ketogenic diet usually aims for under 50 g/day, and some stricter protocols stay below 20 g, to push the liver into making ketones (β-hydroxybutyrate, acetoacetate) and tip the body into ketosis, where fat replaces glucose as the main fuel. Keep in mind that polyols aren't interchangeable. Erythritol subtracts ~100% because it leaves the body unchanged, while xylitol/maltitol only count partially since they still raise glucose. When you're unsure, count half the polyols.

Applications: keto, refractory epilepsy, type 2 diabetes, low-carb industry

Net carbs steer weight loss through ketogenic protocols. They also anchor the treatment of refractory epilepsy in children, which is the original clinical use, dating back to the 1920s at Mayo Clinic, where the diet cuts seizures even after drugs have failed. They guide type 2 diabetes management, since less carb means less insulin demand, and they shape low-carb product development (Quero-Quero Zero, Lacta Zero, low-carb breads from Wickbold and Pullman), which splash "net carbs" or "carboidratos líquidos" across the label. In tracking apps like Carb Manager or Cronometer you set the daily target in net carbs, not total carbs.

FAQ

Are net carbs an official metric? No. Brazilian ANVISA and US FDA both require total carbs on labels. "Net carbs" comes from the low-carb community, not from any regulator.

What is ketosis exactly? It's a metabolic state in which the liver builds ketone bodies from fatty acids and burns them for fuel, and you can measure it as blood ketones > 0.5 mmol/L. Don't confuse it with diabetic ketoacidosis, which climbs to 10–25 mmol/L and is dangerous.

Can I eat unlimited fiber on keto? For practical purposes, yes. Vegetables like broccoli, spinach and avocado are keto staples exactly because their high fiber drags net carbs down near zero.

Why doesn't erythritol count, but maltitol does? Erythritol gets absorbed in the small intestine and leaves through urine without ever being metabolized. Maltitol is partly digested and raises glucose about half as much as sugar (glycemic index ≈ 35).