Oct 4 2011 --- New research, led by psychologists at the University of Bristol, has found that children who are familiar with a snack food will expect it to be more filling. This finding, published (online ahead of print) in the American Journal of Clinical Nutrition, is important because it reveals one way in which children over-consume snack foods and increase their risk of becoming overweight.

Children are at risk of obesity due to consumption of energy-rich snack foods that are often high in calories and associated with weight gain. The study aimed to establish whether familiarity with snack foods (i.e. eating them more frequently) would change the children's expectations about fullness.

Dr Charlotte Hardman, one of the authors from the Nutrition and Behaviour Unit in the University's School of Experimental Psychology, said: "We know from previous work with adults that we have beliefs and expectations about how filling foods will be, and these expectations can change. Moreover, 'fullness expectations' are important determinants of meal-size selection, for example foods that are believed to be more filling are selected in smaller portions."

Seventy 11- to 12-year-old children took part in the study. They used a specialised computer task in order to quantify the fullness that they expected from different snack food products. They also reported how frequently they ate the snack foods.

The researchers found that familiarity helps children to predict the fullness that is associated with snack foods, which, in turn, informs appropriate decisions about portion sizes. The team also discovered that children who were infrequent consumers tended to rely on the physical appearance of the food, for example volume, in their judgments about fullness. This strategy would be expected to promote selection of larger portion sizes.

Dr Hardman added: "Presenting children with a wide variety of different snack food products may make it difficult to predict their fullness. Our study suggests that if parents choose to give snack foods to their children, they may wish to stick to the same products."