Carbs and Net Carbs

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If you’ve been hearing about low-carb and the keto diet, you may be wondering what are carbs and net carbs and why should I care? When you’re on a low-carb or keto diet, carbohydrates are pretty much the first thing you check when looking at nutrition facts. But there’s more to the label than just carbohydrates. Fiber, sugar, sugar alcohols—they’re all listed under carbohydrates. It’s important to know which ones  you should pay attention to so you don’t go over your daily carb limit.

The key to figuring out carb count is calculating net carbs. These are the carbs in food that actually impact your blood sugar. Just beware: There’s no official definition of net carbs, so the net carb count on labels is often deceiving.

When you’re doing a keto or low-carb diet, each gram of carbohydrate counts, so it’s imperative to track net carbs accurately. 

What Are Net Carbs?

Net carbs are the carbohydrates in food that you can digest and use for energy. To calculate net carbs, take a food’s total carbs and subtract:

  • Fiber. Since our body doesn’t have the enzymes to break down fiber, it passes through our digestion system unchanged.

  • Sugar alcohols like xylitol and erythritol. Sugar alcohols taste sweet but their molecular structure is slightly different from that of sugar molecules, which leaves sugar alcohols indigestible. (Note that certain sugar alcohols do impact blood sugar, and you should factor them into your net carb count if you eat a large amount or are diabetic.)

Why Net Carbs Matter 

Carbs are OK in moderation. In fact, most people do better with some quality carbs. Excess carbs—and especially refined carbs like bread, pasta, sugars, etc.—can:

  • Spike your blood sugar

  • Cause inflammation

  • Trigger food cravings

  • Disrupt your hormones

  • Mess up your gut bacteria

  • Contribute to obesity, insulin resistance, diabetes, and metabolic syndrome

So you don’t want too many carbs. A better option is to keep carbs low and eat more good fat. Just be sure to get your fat from good sources like grass-fed animals, wild-caught fish, avocados, olive oil, and pastured egg yolks.

When you keep net carbs low enough—under about 50 grams a day—your body goes into ketosis: a state in which you shift from burning glucose, or carbs, for energy to burning fat, including body fat. On a keto diet, or any other kind of low-carb diet, you must limit the carbs you eat so you can maximize fat-burning and minimize inflammation. That’s why it’s so important to know how to figure out net carbs. If you go over your carb limit, you’ll fall out of ketosis, and lose all the benefits.

How to Calculate Net Carbs

Net carbs = total carbs – fiber – sugar alcohols

Just remember not all sugar alcohols are truly carb-free, and some manufacturers are selling “low-carb” foods that have more carbs than they actually are claiming.

The following sugar alcohols do not count toward net carbs:

  • Erythritol

  • Xylitol

  • Mannitol

  • Lactitol

The sugar alcohols below partially count toward net carbs:

  • Maltitol

  • Sorbitol

  • Isomalt

  • Glycerin

Each gram of maltitol, sorbitol, isomalt, or glycerin counts as about half a gram of carbs, so take the number of grams of the sugar alcohol, divide by 2, and add it to your carb count. For example:

Net carbs = total carbs – fiber – sugar alcohols + (maltitol / 2)

Another thing to note is that your gut bacteria can ferment sugar alcohols, which creates gas and bloating in your small intestine.

Always eat less than 15 grams of sugar alcohols and be wary of mannitol, maltitol, and sorbitol—your gut bacteria love fermenting them.

Everyone is slightly different. What matters is finding the net carb intake that works best for you.