blog 3 plate image

It’s often suggested that people who want to lose weight will eat less if they use smaller plates. However, new research has shown that there’s more to this intervention than you might think.

The theory behind the ‘smaller plate’ approach was that using a smaller plate meant that people would eat smaller serves of food. Since eating just 50 calories extra per day could amount to a weight gain of 2.5 kilograms per year, reducing overall calorie intake by using smaller plates can potentially assist people who are trying to lose weight to eat fewer calories.

In 1900, the average dinner plate was around 24cm. These days, the typical dinner plate is nearly 30cm: a huge jump in size, which also helps to explain how a person’s weight could slowly creep up over time.

The study, published in the Journal of Consumer Research included five different experiments to understand the influence of plate size and colour on serving and eating behaviour.

The experiments were based on a concept known as Delbouf’s theory, which is demonstrated in the following image. If these concentric circles were plates, and the darker circle represented a serving of food, which one is the larger serve?

image for Blog 3 Delbouf's Theory

In fact, the serves are both the same size.

Health and weight loss experts have long recommended that people use smaller plates: in doing so, it is possible to perceive the serving of food to be more generous than if eating the same serving of food from a larger plate.

However, the authors of this study found that people struggle to serve themselves accurate portions and plate size (both large and small) can have a distorting effect.

For example:

• When serving onto a larger plate, participants served themselves larger amount of foods
• When serving foods on a smaller plate (than the control plate), participants underserved themselves relative to the standard portion size
• The colour contrast between the crockery and the food being served also influenced the amount of food served: use of plates which contrast with the colour of the food also result in smaller serving sizes
• Taking time to mindfully serve food portions, rather than doing so in a rush also helped to reduce the overall amount of food served
• Education about the Delbouf illusion reduced the effect of overserving and underserving, but did not entirely eliminate the serving bias caused by larger or smaller plates

Even those who are experts in nutrition are also affected by the Delbouf illusion: when 85 nutrition experts were provided a larger bowl, they also served themselves 31% more food. Similar studies have shown that 97% of people eat all that has been served to them on a plate, which means that by serving smaller portions, it is likely that people will simply eat less food.

As a weight loss professional, explaining this theory and encouraging use of smaller sized plates and bowls is a simple and practical intervention to assist your clients with their weight loss.

Van Ittersum, K., & Wansink, B. (2013). Plate Size and Color Suggestibility: The Delboeuf Illusion’s Bias on Serving and Eating Behavior. Journal of Consumer Research, S20–S33.

Have you suggested that your weightloss clients change their kitchenware? How successful was this in helping them to reduce the amount of food consumed? Share your experiences in the comments below.