Serving Size vs. Portion Size: Which is Which?

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Having diabetes is hard work, especially when it comes to meal planning. In fact, many people with diabetes find meal planning to be the most challenging aspect of having diabetes. There’s so much to think about: carbohydrate, timing of meals, reading food labels, controlling portions… Speaking of food labels and portions, have you ever stopped to think about the difference between a serving size and a portion size? Well, they’re the same thing, right? Sorry, but that’s wrong. It’s important to know the difference between the two, not only for blood glucose control but for weight control as well. Let’s take a closer look.

Consider the term “serving size.” Where do you usually find these words? On a Nutrition Facts label (otherwise known as a food label). In the United States, we’re fortunate to have the nutrition information about a particular food listed on the package or container. Although it can be confusing and time-consuming to read food labels, once you know what to look for, you can breeze through a label in no time. The “serving size” on a food label refers to the amount of that food usually eaten at one time, according to the United States Department of Agriculture (USDA).


What determines serving sizes? Well, the data comes from nationwide food consumption surveys. Foods that are measured in bulk, such as cereal or flour, are typically listed in common household terms, such as cups, tablespoons, teaspoons, or fluid ounces. Foods that are divided up to serve more than one person, such as pizza or cake, are listed in a fractional amount, such as 1/4 pizza or 1/12 cake. Serving sizes for foods that come in “discrete units,” such as bread or cookies, are usually listed as “1 cookie (30 grams)” or “2 slices bread (50 grams).”

No doubt you’ve read a label and shook your head thinking, “There’s no way that just one cookie is a serving size,” or “Who eats just 1/2 a cup of ice cream?” While these serving sizes can certainly seem unrealistic, it’s very important that you always look at the serving size on a Nutrition Facts label because all of the nutrients listed on that label, such as fat, carbohydrate, and sodium, are based on the serving size. If you end up eating twice or three times as much as the serving size, the amount of carbohydrate (along with calories and fat) will double or triple, thereby affecting your blood glucose levels and possibly your weight, too.

You should think about something else when it comes to serving size: If you use the Food Pyramid, food lists, or exchange lists for carbohydrate counting, for example, a “starch exchange” or a “carb serving” is a particular amount of food that provides about the same number of calories and carbohydrate as another, similar food. For example, a 1-ounce slice of bread contains about 80 calories and 15 grams of carbohydrate, the same as in 1/3 cup of cooked pasta. But the serving size on a box of pasta is two ounces (dry). Cooked, those two ounces of pasta yield 1 cup, which contains roughly 45 grams of carbohydrate. Tricky, isn’t it?

A good piece of advice is to always go by what’s listed on the food label, if it’s available, rather than on a food list. And if the food doesn’t have a food label, consider purchasing a good food counts book to look up the grams of carbohydrate. One popular choice is The Doctor’s Pocket Calorie, Fat & Carbohydrate Counter, although there are many other good food counts books available, as well.

So, what’s the difference between serving size and portion size? A serving size is a unit of measure that describes a recommended amount of a certain food. A portion size, on the other hand, is the amount of a food that you choose to eat. For example, a serving size of Fritos corn chips is 1 ounce, or 32 chips. Your portion size, however, might be more like 3 ounces (similar to three handfuls), or close to 100 chips. Portion sizes aren’t necessarily always larger than serving sizes. You might eat only 15 Fritos, and that would be your portion size.

If you tend to do a lot of reading or surfing on the Internet, be careful: Some articles, books, and Web sites use the terms “serving size” and “portion size” interchangeably. They’re not the same.

The moral of the story, then, is always to look at the serving size, whether on a food label or in a food counts book, when meal planning. Doing so will help you mange your diabetes and your weight.

Next week: More on portion control!

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