The Visuals of Dieting: It’s Not Just Size That Matters
November 30, 2011

The Visuals of Dieting: It’s Not Just Size That Matters

Researchers have recently discovered yet another connection between visual cues and the mind´s perception of food quantity, hunger and satiety – this time involving color and contrasts.

It´s no news that the dimensions of your dinnerware can affect your mind´s subconscious estimation of the amount of food it is about to consume. For years researchers and dieticians have urged people to use smaller dishes as part of their weight-loss strategy, thus hoodwinking their brains into believing that they´re eating more than they actually are.

Yet while scientists Brian Wansink and Koert van Ittersum of the Georgia Institute for Technology say that size does matter, their research points out that it´s not the only visual factor that affects your appetite.

A new study published by Wansink and van Ittersum in the Journal of Consumer Research indicates that the relative color contrast between your food and the plate upon which it sits may play an equally important role in helping the brain to gauge the volume of the victuals you´re about to consume.

In instances where there is a low level of color contrast between the food and the plate – like a heap of mashed potatoes on an egg-shell colored plate – people tend to consume more calories. Conversely, a high level of color contrast – such as a bright red pile of marinara-covered noodles in a white pasta bowl – has the exact opposite effect. People will generally put less food on their plate – on average, some 10% less. Moreover, color contrast between the dish and its background (say, the tablecloth or the table´s surface) is equally important.

Researchers have traced the cause of this phenomenon to an optical illusion discovered over 150 years ago. The Delboeuf illusion – so named for its Belgian discoverer Franz Delboeuf – was first noted in 1865, when the researcher noticed that people perceived a size discrepancy between two identical circles when they were framed by larger circles of different sizes. If one of the identical circles was placed inside a just barely larger circle, people believed it was larger than when the same circle placed inside a much larger circle.

Wansink and van Ittersum tested some 200 people between the ages of 18 and 39, re-creating Delboeuf´s illusion by allowing the subjects to fill-up plates and bowls of various sizes with food. As expected, people with oversized dishes tended to dish out more food than their counterparts with smaller plates.

Yet when researchers removed the contrast between the dish and the tablecloth on which it was served, they eliminated the illusion that there was an outside circle. When a white plate was placed on a white tablecloth, people perceived the middle space on the plate or bowel as being smaller and thus served themselves less food. Exactly the opposite was observed when the same-sized dishes were placed on a starkly contrasting tablecloth.

“It´s not simply that the bowl holds more,” explained the study´s lead author van Ittersum. “Even when you give people a specific target amount, they´ll pour more than the target into a big bowl, and less into a small bowl, because of this illusion.”

“If you want to reduce the amount of unhealthy food you eat, you want to choose a plate that really contrasts with it; if you plan to eat healthy food and want to eat more, you want to choose a plate with a lower contrast,” says van Ittersum, an associate professor of marketing at Georgia Institute of Technology.

Significantly, van Ittersum´s team observed that a table-top with a similar hue to the serving dish significantly reduced the tendency of the subjects to over-serve themselves: The Delboeuf illusion redux.

“If you put a white plate on a white tablecloth, the illusion kind of disappears because you eliminate the outside circle and just focus on the inside circle,” says van Ittersum.

Kind of confusing, right? Well, you´re not the only one. Even after researchers explained the illusion to participants in the study, van Ittersum says that they still had a tendency to over-fill and under-fill in exactly the same patterns.

“Even when we tell people, ℠Listen, this illusion takes place, so please be careful when you serve yourself food,´ they still mess up. So at home, it´s especially important to take these preventive measures.”

Van Ittersum suggests that the simplest way to avoid falling prey to the curse of Delboeuf is for people who own large dishes in various colors to simply choose colors that starkly contrast the food being served. It tricks the brain into perceiving the dish as smaller, thus causing you to heap less food onto it. And interestingly, people still tended to feel full and satisfied even with the smaller quantities.

“It could simply lead consumers to satisfy their hunger while unknowingly eating less,” write the researchers in the study. “It may be easier to change our personal environments than to change our minds.”

Oh the powers of the subconscious.


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