You already know that monitoring portion size is an important part of healthy eating. But what about the size of your plate?
According to some studies, a plate’s physical appearance, particularly its size and color, can influence calorie intake. That means that if your kitchen cabinets are filled with large plates, bowls, and glasses, you may be over-serving yourself at meals without even knowing it.
Several years’ worth of research points to a relationship between plate size and how much we serve ourselves. In one study, members of a test group with larger bowls ate 16% more cereal than those given smaller bowls. What’s more, when both groups were asked to estimate the size of the cereal portion they’d just consumed, those with larger bowls estimated they’d eaten 7% less than those with the smaller bowls– even though the participants in the group with larger bowls had eaten more.1 This is just one in a series of studies that suggest eating from larger bowls and plates can cause us unknowingly to eat more at meals than we would if served from smaller dinnerware.
How exactly does the size of a plate influence our impression of how much we’re eating?
A more recent paper investigates this question with five studies that included nearly 200 participants between the ages of 18 and 39. Asked to complete various tasks, including serving themselves Campbell’s soup into bowls of varying sizes, and serving themselves creamy pasta Alfredo in either white or red bowls,2 the study participants misgauged due to what the research suggests may be attributed to a well-known optical illusion first described by Belgian philosopher Franz Delboeuf in 1865.
The Delboeuf illusion proposes that we tend to misjudge the size of identical circles surrounded by circles of varying sizes– if a circle is surrounded by a large outer circle, we perceive it as smaller, but if that same circle is surrounded by a small outer circle, we perceive it as larger. In other words, the more blank space there is around the circle, the smaller it appears.
Now, imagine that optical illusion in the context of filling a bowl up with soup. The diameter of the amount of soup you’ve poured into the bowl will appear smaller if you’re using a very large bowl– the illusion could cause you to pour yourself more soup than you originally intended to.
In a similar vein, the study found that participants tended to serve themselves more when the colors of their food and plates were similar; think, pasta with white Alfredo sauce on a white plate. When their food contrasted with their plate color, this over-serving didn’t happen. The researchers suggest that this may be because contrasting food and plate colors reduce the effect of the Delboeuf optical illusion.
It should be noted, however, that it’s difficult to tie perception of serving size and consumption to one single psychological process. Some separate researchers have said that linking plate size and portion size is too simplified an explanation, and that different cues, like the amount of food available or remaining in a serving dish, may have more of an influence on how much diners serve themselves.3
If you’re already wise to this research and you’ve tried to purchase smaller plates, you may have realized they are somewhat difficult to come by. Over the past several decades, the size of what’s considered normal dinnerware has substantially increased. In the early 1980s, the diameter of a typical dinner plate was roughly 10 in (25 cm). By the early 2000s, the diameter of typical dinner plate increased to 12 in (30 cm)– that’s a surface area increase of 44%. This increase in plate sizes is occurring alongside America’s increasing rates of obesity.
At home, consider serving your main courses on smaller salad size plates to see if it helps you reduce portion sizes without feeling cheated. Or you can simply curb the impulse to fill a large plate all the way up with food by measuring out your portions before plating them. Either way, smart eating requires smart portions– even though plate size is on the rise in America.