Wondering how to stop all that calorie-rich food from going down your throat at mealtimes? Well, the answer is simple -- start having low calorie soup.

A study conducted by researchers at Penn State, US, has shown that people who have low calorie soup before a meal tend to reduce their total calorie intake by 20 percent, when compared to the times they did not eat soup.

Dr Barbara Rolls, who holds the Guthrie Chair of Nutrition at Penn State, said the study was undertaken to find out if different forms of soup might have different effects on food intake.

"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," she said.

As a part of the study, the researchers also tested whether the form of soup and the blending of its ingredients affected food intake and satiety. All 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, doctoral student in nutritional sciences at Penn State and co-author of the research, said the work added weight to earlier studies on the subject.

"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."

However, she warns that people still need to be careful about the kind of soup they pick; higher-calorie, cream-based soups that could actually increase the total calories consumed.

"Make sure to choose wisely by picking low-calorie, broth-based soups that are about 100 to 150 calories per serving," she said.