How the psychology of plate size can affect your diet

By Catherine Orda | Photo by Asnim Asnim /Unsplash

A slew of dieting tricks that have almost nothing to do with food exists: using forks over spoons because it makes you overestimate calories, not eating in front of a TV because distraction makes you eat more, and eating off smaller plates because it significantly reduces meal portions.

Granted, there is some truth to these gimmicks (most of them are proven by scientific research), but every now and then, a new body of evidence arises to render these tricks ineffective.

New studies suggest that plate size as a good dieting strategy is particularly misleading: While smaller plates do let you better control your meal portions, hunger still reigns as the definitive factor that dictates how much you’re bound to eat. That is, how much you eat still ultimately depends on how hungry you are—regardless of plate size.


The Delbouef illusion

The idea that small plates can reduce your consumption is based on the Delbouef illusion, which is a psychological phenomenon that affects the way we perceive two circles of identical size relative to the size of the circle that contains it. The theory goes that the inner circle will always appear smaller if it’s contained in a bigger circle. In the context of food, this means that if you put a burger on a big plate, you won’t think that it’s a lot of food. Put the same burger on a much smaller plate, and you’ll think that it is [a lot of food]. This illusion can reportedly reduce the amount of calories you eat by up to 29 percent.

The Study: Portion control doesn’t work when you’re really hungry

A new study from Ben Gurion University found that this illusion doesn’t always hold. Tzvi Ganel, the head author of the study, found that the extent of the Delbouef illusion’s effect on portion control largely depends on how hungry you are. “It’s more difficult to trick the brain via illusions when food is in need,” said Ganel to Fast Company. This means that the hungrier you are, the less likely you’ll be affected by the illusion. In other words, plate size ultimately doesn’t do anything for portion control if you’re really hungry.

You always need to listen to your body. It’s good to push yourself, but no weight loss or fitness goals are worth starving yourself over

According to the study, this is because your brain naturally goes into survival mode once it detects hunger. Your brain fights off the Delbouef illusion in order to save your life. “[This adaptive phenomenon] allows humans to effectively evaluate objects of interest when such objects can be vital for survival,” said Ganel.

So what do we make of this research? It might be an obvious and underwhelming conclusion to make, but dieting tricks become less effective when hunger strikes. But there’s an underlying message here, which is that you always need to listen to your body. It’s good to push yourself, but no weight loss or fitness goals are worth starving yourself over.

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