A new article published in the Journal of Consumer Psychology suggests that people perceive food that weighs less as healthier than their heavier counterparts of the same serving size. According to the researchers who conducted the study – Yi Li, Nico Heuvinck, and Mario Pandelaere, the bias is a result of coactivation of two meanings of the word “light”.
Food can be “light” in terms of physical weight; but also, several food items have “light” versions that are low in calorie content. A food item with a “light” label according to FDA guidelines needs “to have a third fewer calories, or no more than half the fat of the original version of the product”. The researchers hypothesized that when people encounter the label “light” (low in calories), the other meaning of the word gets automatically activated and vice-versa.
In one of the studies conducted to test the bias, the researchers found that people implicitly associated images of high-calorie food (e.g., hamburger, potato chips) with words that mean “heavy-weight”, and low-calorie food images (e.g., veggie burger, oatmeal chips) with words that mean “light-weight”.
In another study, researchers asked participants to choose ingredients for a hypothetical chicken Caesar salad. They were told that the person in the thought experiment (Susan) who made the chicken salad intended to make a 300g portion. But, despite following a recipe for 300 g and using the same amount of ingredients, Susan ended up with a salad weighing significantly more or less than 300g. Participants chose from among a list of ingredients, either a regular item (fried chicken, regular cheese, regular bacon) or a healthier alternative (grilled chicken, fat-free cheese, fat-free bacon).
When they were told that the salad weighed less (250g), participants disproportionately chose the healthier alternatives as ingredients. When they were told it weighed more than intended (350g), they disproportionately chose the regular (less healthy) alternatives. In another study, researchers found that the opposite was also true. Participants estimated the weight of a cake made from regular ingredients (e.g., whole milk, sugar) to be more, on average, than one made from healthier ingredients (e.g., nonfat milk, stevia).
Researcher also found that people were more likely to doubt the health claims of a hypothetical “light” product (Kraft light mayonnaise) if it comes in a container that weighs more than a container of the “regular” version (Kraft mayonnaise).
In one study, participants who were given two bowls of M&M’s ate more of the candy from the bowl that was lighter. The bowls were identical, except one bowl had a hidden weight stuck to its bottom. They were told that one of them contained a healthier version of M&M’s and asked to identify the bowl. Participants disproportionately chose the M&M’s in the lighter bowl as the healthier version, and snacked on it significantly more when told they were free to eat from both bowls.
Finally, researchers found a way to reverse this (light=healthy) bias. They presented participants with two versions of the same energy bar (same serving size and brand). According to labels on the energy bars, one of them weighed more and contained more proteins. Crucially, the difference in protein content was proportional to difference in physical weight. In this condition, consumers disproportionately chose the heavier bar as the healthier version, presumably because they perceived the weight difference as attributable to higher protein content.
Read more about the study here.
