The popular dieting technique of using smaller plates to reduce the amount of food one consumes in each meal probably doesn’t work, Israeli researchers from Ben-Gurion University of the Negev have found.
The technique is based on the so-called Delboeuf illusion, one of several relative-size illusions identified by researchers, in which the brain believes a circle is larger if a surrounding border is smaller.
So, a plate with a larger rim, or simply a larger plate, makes a meal appear smaller, while the opposite makes it appear larger. To eat less — researchers have suggested in past studies — use smaller plates, which makes the amount of food on the plate appear more than it is and reduces the amount you’ll actually eat.
But according to researchers Dr. Tzvi Ganel and PhD candidate Noa Zitron-Emanuel of Ben-Gurion’s Laboratory for Visual Perception and Action, that may not be true.
The researchers, who have published their study in the upcoming edition of the medical journal Appetite, “utilized size-contrast visual illusions commonly associated with food to explore the way deprivation [i.e., hunger] affects relative processing of food size,” they write in the September 1 edition of Appetite.
They conducted two experiments, one with 32 women and the other with 41 women and 40 men — both groups had a mean age of 24, suggesting the subjects were likely Ben-Gurion University students — to test how hunger affected participants’ perception of the size of food and a non-food object in the context of different-sized objects. They gave the participants slices of pizza on different-sized trays and divided the responses according to the relative amount of time that had passed since each participant had eaten.
Their conclusion: “Food deprivation reduces the illusory bias for food-related but not for neutral stimuli.”
That is, your brain falls for the Delboeuf illusion every time — except when it’s hungry and looking directly at food. Then the brain gets serious, and seems able to discern exactly how much food is in front of it regardless of the size of the dish it’s in.
Or, in the researchers’ words, “Such reduction in the illusory effect indicates reliance on analytic, rather than on relative processing style, for domain-specific stimuli when in the state of hunger.”
“We have a study in which we showed that when we are hungry, we are more precise in knowing exactly when the food portion changes,” Ganel is quoted as saying by the No Camels website. The Delboeuf illusion “is misleading. It’s [an] inaccurate perception. It makes sense that we won’t be inaccurate when we need the food. The plate is not the part that we are interested in. It’s the food.”
The same wasn’t true when researchers tested the same participants using drawings of circles and hubcaps. There the Delboeuf illusion held firm.
The researchers plan to expand the research “to take this knowledge to patients” suffering from various eating disorders, “and once we establish baselines for normal perceptions of food, we will test it against other populations to see how they perceive food,” Ganel said.