Carb tracking on the keto diet can be confusing. Do you track total carbs? Net carbs? Is reading the nutrition label sufficient?
These are all questions that will be answered in this article.
Today you’ll get a primer on net carbs: What they are, the benefits of using this metric, and how to track keto net carbs.
But first, let’s talk about carbs on keto generally.
Why You Need To Limit Carbs On Keto
On a ketogenic diet, you eat about 60 to 70 percent of calories from fat, 20 to 30 percent from protein, and under 10 percent from carbohydrates.
This last rule—keeping carbs low—is the crucial one. It’s the initial spark that sends you into fat-burning ketosis.
Why? Three simple steps:
- Keeping carbs low keeps blood sugar low (Carbs raise blood sugar MUCH more than fat or protein)
- When blood sugar stays low, the hormone insulin stays low
- Low insulin sends the ketosis bat signal to cells in your liver, then your liver starts burning fat and making ketones
Pretty neat chain of events. And it’s all because you stopped eating carbs.
What Are Net Carbs?
Net carbs are the only carbs that count on keto.
Specifically, net carbs refers to carbohydrates that are digested through normal routes. These carbs are absorbed through the small intestine, metabolized, and end up in your blood as blood sugar.
Net carbs include both simple and complex carbohydrates. In the simple carb category are glucose, galactose, and fructose—sugars found in candy, sodas, and table sugar. These simple sugars have a high glycemic index, meaning they raise blood sugar rapidly and significantly when digested.
Complex carbohydrates—which are just simple carbs molecularly bonded together—have a lower glycemic index than simple carbs, and have a smaller (though still keto-unfriendly) blood sugar impact. Foods high in complex carbs include apples, lentils, and whole grains.
In summary: Net carbs = Simple carbs + complex carbs
But not all carbs fall into these categories. Fiber and sugar alcohols aren’t digested through normal routes, so they don’t significantly raise blood sugar and insulin levels. So unlike most carbs, they aren’t keto kryptonite. They aren’t counted as net carbs.
With this in mind, the more useful (and well-known) net carbs equation is:
Net carbs = total carbs - fiber - sugar alcohols
That’s the equation needed for food-label math.
Digesting Carbs from Fiber and Sugar Alcohols
By now you’re probably wondering why fiber and sugar alcohols are so special. Why, exactly, don’t they count towards your keto carb limit?
Let’s take fiber first. Fiber may be indigestible (not absorbed), but it still has two main purposes in your body:
- To feed gut bacteria and promote a healthy gut microbiome
- To help you stay regular
One class of fiber, called soluble fiber, helps with both these functions. It passes through the small intestine, fueling gut bacteria in your colon—which in turn produce anti-inflammatory compounds like butyrate. Insoluble fiber, on the other hand, passes through the entire gut, and primarily helps with function #2. (Pun not intended!).
What about sugar alcohols? Like fiber, sugar alcohols generally have a negligible impact on blood sugar. To be clear, however, it depends which sugar alcohol you’re talking about.
Xylitol and maltitol, for instance, have a measurable glycemic index, meaning they affect blood sugar levels when ingested. Xylitol has a glycemic index of 13, while maltitol has a glycemic index of 35. (For reference: pure sugar has a GI of 65).
Erythritol, however, has a glycemic index of zero—no blood sugar impact. Also interesting: Early human evidence suggests that erythritol supplementation improves blood vessel function in diabetics.
Benefits Of Eating Low Net Carb
Keeping net carbs low keeps you in ketosis. This unique metabolic state has many potential benefits, from enhanced fat burning to better energy to improved focus.
Beyond these benefits, however, let’s review the advantages of measuring net carbs instead of total carbs on keto. Both will keep you in ketosis, but using net carbs helps you:
Tracking Net Carbs
Tracking net carbs isn’t super complicated, once you get the hang of it.
To start, use a macro calculator that takes into account net carbs. Just input your gender, activity levels, weight loss goals, and other metrics—and it spits out your daily allotment of net carbs, usually somewhere around 20 grams per day.
Now comes the fun part: Logging your meals! Just kidding, but with the benefit of smartphone technology, food tracking can be both easy and enjoyable. (Here’s a list of our favorite keto apps).
After a few days of dedicated tracking, you’ll get an intuitive sense for the net carb content of different foods. Here are a few examples: (Source: USDA food database)
- Net carbs in broccoli: 3.4 grams net carbs per 100 grams broccoli
- Net carbs in onions: 7.6 grams net carbs per 100 grams onions
- Net carbs in avocado: 2.6 grams net carbs per avocado
- Net carbs in carrots: 6.7 grams net carbs per 100 grams carrots
Some of these foods, obviously, are more keto-friendly than others. But interestingly enough, the lowest net carb food on this list—the avocado—is one of the highest in total carbs.
That’s because most of the carbs in an avocado are from fiber. When we calculate net carbs, we back that fiber out.
Low Net Carb Shopping
Yes, lots of foods don't fit well into a keto diet. (Groan!). But thanks to the beauty of nutrition science and zero calorie sweeteners, many of your favorite carby foods are now keto friendly. You can make keto brownies, munch on keto granola, and even whip up keto s’mores!
When it comes to finding keto-friendly packaged foods, label reading is key. Look for companies that:
- Don’t use refined sugar
- List net carbs out to the first decimal
Number two means looking for companies that go beyond the standard nutrition label. The standard nutrition label rounds everything to whole numbers, which makes it impossible to accurately calculate net carbs.
For example, you could calculate 1 gram net carbs based on the label, when a product has closer to 2 net carbs per serving. That adds up over time!
For a visual example of this phenomenon, check out this handy guide to net carb math.
Your Low Net Carb Journey
You’re officially a net carb expert now. You know what net carbs are, and you know how to track them like a pro.
This knowledge will serve you well on your low-carb journey. Come back for a refresher anytime.