The Sneaky Math That Undermines Calorie Counting

Let’s say you’re choosing between two meals: a hamburger or a hamburger with a side of broccoli salad. Even though the combination of the two contains more calories (or Joules for that matter) and may run up against your goals of reducing energy intake, many of us mistakenly believe that the combination of healthy and indulgent—a hamburger plus a salad, or a candy bar plus an apple—is healthier than the indulgent item alone.

This kind of health halo is known as the “averaging bias,” as Alexander Chernev and Pierre Chandon explain in "Calorie Estimation Biases in Consumer Choice" (PDF). Merely adding a “healthy” option to menus can lower the overall perceived calorie content—a trend, USA Today reports, that many chain restaurants are embracing.

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Still, if numbers and statistics have this leveling effect, new mandatory calorie disclosures—coming soon—could tackle the bias on one condition: if we understand the unit of measurement.

You see, large numbers can trick us into thinking they represent large quantities. Hence, a warranty expressed as 84 months appears longer than a 7-year warranty, although they’re equal, as researchers demonstrated in a forthcoming article on the “unit effect” in the Journal of Consumer Research.

When it comes to food, the researchers offered participants a complimentary apple or a Twix labeled with two different units of measurement—Kilocalories (above) or Kilojoules (below). The authors write, "Participants more often chose the apple when the energy content was expressed in Kilojoules than in Kilocalories [because] the former difference (782 Kilojoules) looks much bigger in the latter one (187 Kilocalories).” In other words, a metric measuring system for food energy made the lower energy content of an apple appear larger, when compared to a candy bar.

Food manufacturers have knowingly marketed low-fat foods that don’t necessarily have fewer calories than the full-fat versions, or emphasize seemingly large quantities of micronutrients (fortified with Vitamin D!) in cereals that contain a lot of macronutrients (sugar!). Now, what if these were used to trick us into changing our behaviors for better? Can this kind of quantitative thinking about food be put to better use?

Let us know what you think and stay tuned, we’ll be launching a food label redesign contest that will incorporate some of these ideas in the upcoming weeks.