Mind games: How your eyes can trick you into eating too much

How much of what you eat is just because that's what you have in front of you? To help answer this question, respected academics Brian Wansink, James Painter and Jill North Craft conducted a now-famous experiment called "bottomless bowls," which illustrated how visual cues can play an important role in preventing unintentional overeating. Here's what they learned.

Half of the research participants were served soup in a normal bowl, while the other half were served in a bowl that filled itself by means of a hidden mechanism. The refilling bowls gradually and indiscernibly filled up again as their contents were consumed. The researchers then gathered info on how much the participants thought they had eaten, how much they'd actually eaten, and how full they felt afterwards. The results are astonishing!

Participants ate 73% more, but didn't believe they were any fuller

In the researchers' words: "We found that the participants who were unknowingly eating from self–refilling bowls ate 73% more soup that those eating from normal bowls. However, [these] participants did not believe they consumed more, nor did they perceive themselves as more sated than those eating from normal bowls. This effect remained regardless of [their Body Mass Index]."

"When there was an accurate visual cue as to how much one had eaten, people stopped eating at an earlier point than when there was a biased visual cue of what they had eaten. Since people use their eyes to count calories and not their stomachs, the use of smaller bowls is an important tool for guiding consumption habits."

When bigger isn't better

This experiment shows that, no matter who you are, the amount of food you see in front of you influences how much you expect to eat, and how much you eventually eat. Bigger servings in bigger plates, bowls and glasses could have you eating and drinking much more than you should, and thinking nothing of it - in other words, mindless eating.

So it's not just important to divvy up your food into recommended portions, but also to teach yourself accurate visual cues. This way, even when you’re being served in dish sizes that are unfamiliar to you, like at a friend's house or at a restaurant, you can estimate when to stop.

How to practise portion caution

If you can't count on your usual plate to guide you, here are some visual cues for recommended portion sizes per meal. These general guidelines can help you decide when to stop eating (and pack or give away the rest):

What size should your food portion be?

"Remember, the total number of portions your body needs throughout the day is very personal - it depends on a number of factors, like your gender, metabolism rate and activity level. But everyone needs at least five portions of fruit and vegetables a day," says Terry Harris, a dietician at Discovery Vitality.

Mindful eating starts with being conscientious about what (and how much) you consume at every meal. To learn how many daily food portions you need, invest in your body's health by going to visit a dietitian, who will help you with an eating plan that suits your lifestyle and preferences.