There are lots of factors that affect the amount that people eat. It is now well-known that large plates will lead people at a buffet to fill them with more food than small plates and so they end up eating more. Large portion sizes at restaurants cause people to eat more than they would if the portions were smaller. These aspects of are interesting, because people are often unaware that they are being affected by them.

A paper in the October, 2010 issue of the Journal of Consumer Psychology by Adriana Madzharov and Lauren Block adds something else to this list: the number of items shown on the packaging.

Many snack foods show a picture of what the product looks like. A box of chocolate chip cookies will show sample cookies on the front. A bag of pretzels will show pictures of the pretzels. A box of crackers will show the crackers.

The studies in this paper make three main points.

Second, when given the chance to actually eat, people ate more food from packages with many items pictured on it than from packages with few items pictured on it. That is, the beliefs that the package has more in it and that the portion size is larger led people to consumer more food.

Third, this effect was strongest for people who say that they like to think visually. People often display preferences for the way they like to learn new things. In a final set of studies in this paper, the authors had people rate how much they like to think visually. Those people who were high visual thinkers were much more likely to overeat from packages depicting many food items than people who do not characterize themselves as visual thinkers.

What can you do about this? If you are trying to avoid overeating, you really need to use your environment to help you eat smart. Here are two suggestions. First, you should minimize the number of snacks you keep at home. If there is no snack food in the house, you can't eat it. Second, when you do decide to snack, don't rely on the package to guide you in the amount you eat. Instead, take out a small bowl and put the snack food in it. Put the package away and only eat what is in the portion you set out.

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