The amount of food you eat is affected by the size of the portion you get. At restaurants, for example, people generally eat what is on their plate. So the more food they are given, the more that they will eat. This is a particular problem because obesity rates are rising worldwide. We need to find ways to help people eat less food. Portion size seems like a great place to start.

There are lots of ways to influence portion size. At home and at buffet lines, it is helpful to use small plates. You tend to put enough food on a plate to fill it, so using a smaller plate leads to smaller portions.

In addition, restaurants often offer portions of different sizes. At high-end restaurants, for example, steak-eaters may choose the size of the steak they order. At fast-food restaurants, there are often specific sizes of drinks and fries that are available.

An interesting study by David Dubois, Derek Rucker, and Adam Galinsky in the April 2012 issue of the Journal of Consumer Research suggests that the size of a portion that someone orders can be influenced by their need to enhance their status. The idea is that in many situations, bigger portions are seen as reflecting higher status than smaller portions. When people are feeling powerless, they often want to make themselves feel better by enhancing their status. Ordering a larger portion is one way to do that.

The researchers started by confirming that people generally viewed people who were eating larger portions as having higher status than those eating smaller portions. Next, they looked at the relationship between feeling powerless and portion size.

In one study, participants were residents of an apartment building. The researchers set up tables in three different lobbies of the building. Each table was set up to look like it was advertising a new bagel restaurant in town that was giving out free samples. One table had a sign saying, "We all feel powerless in the morning, treat yourself to free bagels." One table had a sign saying, "We all feel powerful in the morning, treat yourself to free bagels." A third (control) table said "It's morning, treat yourself to free bagels."

On the tables were two bowls with bagel pieces. In one bowl, the bagel pieces were cut in small cubes, and in the other, the bagel pieces were cut into large cubes. People coming to the table were told to take as many bagel pieces as they wanted, but they had to eat them at the table. The people who were at the "powerless" table were more likely to take large bagel pieces than those at the other tables. As a result, they ate more. On average, people at the "powerless" table consumed about 100 calories' worth of bagels, while those at the other two tables consumed about 70 calories' worth of bagels.

Two other experiments in this series extended the results. One study showed that people were most likely to order large portions when they felt powerless and were eating in a social situation. If they felt powerless and were eating alone, then they did not order large portions. This finding suggests that people are selecting portions in part based on the status that those portions may give them.

Finally, the researchers created a situation in which smaller portions signal higher status. In this case, they had participants in the lab read an article suggesting that thinner people are more likely to be successful in business than fatter people. The experimenters manipulated the feeling of powerlessness by having people imagine either that they were an employee who had to do what their boss wanted them to do (a powerless position) or that they were a boss who could tell their employees what to do (a powerful position). At the end of the study, participants were able to select from among different sizes of Toblerone candy bars. In this study, participants who thought that being thinner conveyed higher status selected smaller candy bars when they felt powerless than when they felt powerful.

Putting these findings together, then, it seems that in general people think that larger portions convey more status than smaller portions. As a result, people may overeat in order to increase their status compared to other people.

If we want to help people to eat less food, then there are a few things we can do. First, these studies suggest that we can help people to see that being thin can also convey status. In that case, the need to show status can actually get people to select smaller portions. Second, people who are concerned about their portion sizes should focus on the aspects of their life in which they have control in order to minimize the need to show status through food.

For more by Art Markman, Ph.D., click here.