One Size Doesn’t Fit All: How Serving Sizes Are Calculated

As people become more conscious of what food is going into their body, measuring macronutrients, micronutrients, and calories has become increasingly popular. Most packaged foods in the United States carry labels providing such nutritional information on their label. At the back of the packaging is the Nutrition Facts Label which has an important component displayed - the serving size. The best way to interpret how much nutrition you are consuming requires us to understand the typical serving size each individual has consumed of that food product. Based on how many serving sizes you eat, you can calculate how much nutritional value you have consumed as indicated on the label.

(Feller, 2025)

What is a "Serving Size" and who calculates it?

In the United States, the FDA oversees how much food makes up a serving size—a quantity that is highly dependent on what type of food it is. The FDA explains, "Serving sizes must be based on the amount of food people typically consume, rather than how much they should consume. Serving sizes reflect the amount people typically eat and drink” ("Serving Size", 2024). The FDA uses the National Health and Nutrition Examination Survey (NHANES) to estimate the amount of each food the average American, eats in one sitting. This survey, run by the CDC, runs interviews, physical exams, and laboratory tests, collecting data from randomly selected people to better understand everything regarding their health. These serving sizes are simply the averages of the survey's results, an approximation of how much each person eats in one sitting ("About NHANES", 2024). It’s important to understand that the serving size is not a recommendation of how much to eat, but just a standard unit of measure for all foods. 

Why is Serving Size So Important?

The serving size is so useful because it allows people to compare similar products, and it gives context to all the numbers on the nutritional label. By using this unit of measure, people can easily compare products to determine which is healthier, offers more protein, or better meets their nutritional needs, allowing them to make smarter, more informed choices about what they eat (Food Portions, 2021).

(Falkenheimer, 2021)

Key Takeaways

For us to regulate our food intake, it is important to understand the food labels and specifically serving sizes. With obesity and diabetes on the rise due to the addictive nature of certain foods, we should limit our consumption and monitor the effects of unhealthy foods. Serving size allows us to connect how much food we consume with the various nutritional measures of it, giving us a quantitative understanding of the quality and amount of food we eat.

References

1. CDC. (2024, December 18). About NHANES. National Health and Nutrition Examination Survey. https://www.cdc.gov/nchs/nhanes/about/index.html

2. Falkenheimer, A. (2021, August 18). Compare Serving Sizes—Easy Food Health Decisions. Eatiquette. https://eatiquette.io/compare-food-serving-sizes/

3. Feller, M. (2025, January 24). I’m a Registered Dietitian, and These Are the Only Things I Look for on Nutrition Facts Labels. Kitchn. https://www.thekitchn.com/how-to-read-nutrition-facts-label-23705776

4. Food Portions: Choosing Just Enough for You - NIDDK. (2021, July). National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/weight-management/just-enough-food-portions

5. Serving Size on the Nutrition Facts Label. (2024). FDA. https://www.fda.gov/food/nutrition-facts-label/serving-size-nutrition-facts-label