How Do We Measure Portion Sizes?

Figuring out how much food someone eats sounds simple—but in nutrition research, it’s one of the hardest parts! In the Fuel 2 Fight study, researchers worked with career firefighters to see how portion sizes were reported during 24-hour diet recalls.

Participants shared what they ate either face-to-face with a Nutritionist or over the phone. To describe portion sizes, they used different methods:

• Weights (like grams or ounces)

• Household measures (cups, spoons, etc.)

• Servings & items (like “two slices of bread”)

• Food models (pictures or objects representing food amounts)

  
  

The study found that:

• Face-to-face recalls often used two-dimensional food models (like flat pictures).

• Telephone recalls leaned more on household measures and servings/items.

The big takeaway: When people can’t use food models—like during phone interviews—everyday objects with known sizes (think a baseball, deck of cards, or water bottle) could help them estimate portions more accurately.

Why it matters: Getting portion sizes right is key to understanding diets and improving nutrition advice. By testing different ways to measure food, researchers can make diet studies more reliable—and help us all better understand what we’re really eating.

Read more at Procedia Food Science.

Written by Amber D. Brown, Deirdre D. Douglass, Sara A. Jahnke, W. S. Carlos Poston, C. Keith Haddock, and R. Sue Day.

“My Fries were the Size of an iPhone®”: How Portion Size is Reported in the Fuel 2 Fight Study,

Procedia Food Science, Volume 2, 2013, Pages 129-133, ISSN 2211-601X,

https://doi.org/10.1016/j.profoo.2013.04.020.

(https://www.sciencedirect.com/science/article/pii/S2211601X13000217)

Abstract: Capturing portion size estimates is a constant challenge. Our objective was to characterize reported portion size during face-to-face and telephone 24-hour diet recalls among career fire fighters in the Fuel 2 Fight study. Trained nutritionists reviewed recalls and categorized reported portion size into weights, household measures, servings & items (including common alternatives for portion size), or food models. Two-dimensional models were most frequently used in face-to-face recalls, whereas household measures, and servings & items were more frequently used in telephone recalls. Thus, expanding use of common non-food objects with a known volume could be an important portion size alternative for telephone recalls.

Keywords: portion size; 24-hour recall; servings; food models