The “Understanding Portion and Serving Sizes” survey of 1,000 U.S. adults first asked whether they had an understanding of the two terms. 91 percent said they had at least some understanding about “serving size,” while 90 percent said the same of “portion size.”

Respondents were then given a list of possible definitions that included the most accurate descriptions for both serving size and portion size and were asked to pick the two descriptions that best align with their understanding. (Serving size is based on a standardized amount of a food or beverage that people typically consume in one sitting, while portion size is the amount of food or beverage someone chooses to eat in one sitting.)

Among those claiming knowledge of serving sizes, about half (48 percent) picked the correct definition (the amount typically consumed) and/or thought it was defined by the company that created the product (46 percent). Fewer (39 percent) believed that the term was defined by dietitians and health professionals, while 33 percent thought it was defined by government agencies like the FDA, and 33 percent believed it was the amount one chooses to consume (i.e., the portion size).

But out of those claiming at least some understanding of portion sizes, the most popular definition (“a standardized amount typically consumed”) was the same as the serving size—identical at 48 percent—indicating that consumers essentially conflate the two terms. Slightly behind, 45 percent correctly identified it as the amount one chooses to consume, which was followed by “defined by dietitians and health professionals” (44 percent).

Defining the difference: consumer trends

Respondents were then shown complete definitions of both terms. When asked how their understanding of portion and serving sizes had changed after reading the definitions, about one-third (34 percent) said they understood much more and nearly another third (30 percent) said they understood somewhat more. These results demonstrate a significant knowledge gap in the difference between portion and serving sizes, despite most people believing they have a cursory understanding of the terms.

Consumers who were more likely to say that they understood “much more” after reading the definitions included men (41 percent, vs. 27 percent of women), those earning $80K+ (47 percent, vs. 26 percent earning less than $40K), those under age 45 (43 percent, vs. 26 percent age 45-64 and 25 percent age 65+), and those with college degrees (40 percent, vs. 28 percent no college degree).

By definition, serving sizes are not explicit recommendations for how much to eat. And yet, it appears that most people use them for that purpose, regardless of type of food. For example, 57 percent try to eat the designated serving size for dairy products at least sometimes, while 22 percent rarely or never do.

Focusing next on portion sizes, respondents were asked about why they pay attention to them. “Helping to control weight” ranked in the top two reasons for 36 percent, followed by “helping to avoid eating too much of certain foods” (30 percent) and “helping to know how much they should be eating or drinking” (26 percent).

Sizing up the terms: portion control

The ways people control their portion sizes vary: Similar numbers said they try to eat more slowly (34 percent), stop eating once they feel full, even if there’s still food on their plate (34 percent), use smaller plates/bowls to reduce portion size (32 percent) and choose single-serve portions (31 percent).

In contrast, one in six (17 percent) say they don’t pay any attention to portion sizes, with people over the age of 45 and those that make less than $40,000 per year are more likely to belong to this group. Of them, the vast majority (71 percent) chose “don’t want to be too restrictive on how much they eat or drink” among their top two reasons. One-third (33 percent) said it is more important not to waste food than to have the right portion size.

Overall, these results paint a picture of consumer confusion about portion and serving sizes. Despite having distinct definitions, many Americans use these terms interchangeably, highlighting an educational opportunity to help consumers better understand our food choices.

Methodology

Results were derived from an online survey of 1,000 U.S. adults, ages 18+, by Lincoln Park Strategies. It was conducted from Nov. 4–Nov. 9, 2021, and results were weighted to ensure proportional representation of the population.