The Atkins Diet is arguably the mother of all low-carbohydrate diets. Since its introduction in the 1970s, the diet has undergone some changes to its structure, but one thing remains the same -- when following the diet, you count net carbohydrates rather than total carbohydrates. Of course, in order to calculate net carbohydrates, you first have to know what they are.
The Introduction of Net Carbohydrates
According to Michelle Dudash, a registered dietitian and author of the book "Clean Eating for Busy Families," the term "net carbohydrates" was actually invented by food manufacturers in response to the low-carbohydrate diet craze. The term is not regulated by the Food and Drug Administration and has no official definition. Because of this, you'll never see "net carbohydrates" listed on a nutrition facts panel. You may, however, see it splattered on the front of low-carbohydrate diet foods.
Total Carbohydrates Vs. Net Carbohydrates on Atkins
Total carbohydrates include all types of carbohydrates -- from fiber to sugar to sugar alcohols to starches. All of the different types of carbohydrates have varying effects on your blood sugar levels. Some cause a rapid increase (and resulting drop), while others have little to no effect. While the term "total carbohydrates" doesn't discriminate, the term "net carbohydrates" only includes the carbohydrates that have a significant impact on your blood sugar levels -- like sugars and starches but not fiber. The Atkins philosophy is that because foods that are low in net carbohydrates don't have a significant impact on your blood sugar response, they don't impede weight loss.
How to Calculate Net Carbs for Packaged Foods
Manufacturers are required to list the total amount of carbohydrates on the nutrition facts panel. Underneath the total carbohydrates, you'll also see separate rows for total grams of fiber, sugar and sugar alcohols. According to the Atkins website, you can easily calculate the grams of net carbohydrates by subtracting the amount of fiber and sugar alcohols from the total amount of carbohydrates: net carbs equal total carbs minus fiber and sugar alcohols. For example, if a packaged food contains 25 grams of total carbohydrates, 5 of which come from fiber and 7 of which come from sugar alcohols, then the net carbohydrates would be 13 grams: 25-(5+7)=13.
Calculating Net Carbs for Whole Foods
To calculate net carbohydrates for a food without a package, you'll need to do a little detective work. You'll have to use a nutrition facts counter, like the USDA National Nutrient Database, to determine the carbohydrate breakdown for a specific food, like an apple. You'll need to know the grams of total carbohydrate, grams of fiber and grams of sugar alcohols, if any. Once you have the nutrition facts, the calculations are the same.