Washington, D.C. -- Eating low-calorie soup before a meal can help cut back on how much food and calories you eat at the meal, a new Penn State study shows.

Results show that when participants in the study ate a first course of soup before a lunch entree, they reduced their total calorie intake at lunch (soup + entre) by 20 percent, compared to when they did not eat soup.

This study expands on previous studies about consuming lower-calorie soup as a way to reduce food intake, said co-author Barbara Rolls, who holds the Guthrie Chair of Nutrition at Penn State. Earlier work suggests that chunky soup may be the most filling type of soup, so the purpose of this study was to determine whether different forms of soup might have different effects on food intake.

The study tested whether the form of soup and the blending of its ingredients also affected food intake and satiety. All of the soups tested in the study were made from identical ingredients: chicken broth, broccoli, potato, cauliflower, carrots and butter. However, the methods used to blend the ingredients varied, so that the form of the soup changed. Soups tested included separate broth and vegetables, chunky vegetable soup, chunky-pureed vegetable soup and pureed vegetable soup.

While researchers thought that increasing the thickness or the amount of chewing required may have made certain forms of soup more filling, results of the study show that low-calorie soup is filling regardless of its form.

Julie Flood, a doctoral student in nutritional sciences at Penn State, and Rolls presented their findings May 1, at the Experimental Biology Conference in Washington, D.C.

Consuming a first course of low-calorie soup, in a variety of forms, can help with managing weight, as is shown in this research and earlier studies. Using this strategy allows people to get an extra course at the meal, while eating fewer total calories, said Flood. But make sure to choose wisely, by picking low-calorie, broth-based soups that are about 100 to 150 calories per serving. Be careful of higher-calorie, cream-based soups that could actually increase the total calories consumed.

The research was supported by a grant from the National Institutes of Health.

The concept of "Volumetrics" -- eating a satisfying volume of food while controlling calories and meeting nutrient requirements -- is based on a series of studies led by Rolls in her Laboratory for the Study of Human Ingestive Behavior. This spring, the paperback edition of her book "The Volumetrics Eating Plan: Techniques and Recipes for Feeling Full on Fewer Calories" is being published by HarperCollins.