Portion Size versus Serving Size. What’s the Difference?

Most people mistake portion size for serving size. What's the difference?

Portion size is the amount you choose to put on your plate. Serving size is a standard measurement of a particular food such as a cup or an ounce, determined by government food/health department experts.

For example, one bagel often constitutes at least 2 servings, but most people eat the whole thing, thinking they have eaten one serving.

It’s important to know the difference between the two terms. Let’s take a closer look.

Consider the term “serving size.” Where do you usually find these words? In most countries, the nutrition information about a particular food is 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.

What determines serving sizes? The data usually 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, fluid ounces, grams or milliliters. 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 (120 ml) of ice cream?” While these serving sizes can certainly seem unrealistic, it’s important that you always look at the serving size on a label as all of the nutrients listed on that label, such as fat, carbohydrate, and sodium, are based on that serving size. If you end up eating twice or three times as much as the serving size, the amount of all nutrients (including calories and fat) will double or triple.

If you use exchange lists for carbohydrate counting, 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 (28 gram) slice of bread contains about 80 calories and 15 grams of carbohydrate, the same as in 1/3 cup (80 ml) of cooked pasta. However, a typical portion size of cooked pasta is about 1 cup, not 1/3 cup, which contains more than 15 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 an exchange list.

Let’s look at another example; a serving size of corn chips is 1 ounce (28 grams) or 32 chips. Your portion size, however, might be more like 3 ounces (85 gram, similar to three handfuls). Portion sizes aren’t necessarily always larger than serving sizes. You might eat only 15 chips, 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 on a food label. Doing so will help you manage your calorie and nutrient intake.

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