Labels listing energy density - the number of calories per ounce - do not encourage overeating the way "low fat" labels are suspected of doing, a study from Penn State university in the US has shown.
In the study, 40 normal weight women ate the same amount of food when their meals differed in calories by as much as 29 per cent- even when they were given labels that told them there were fewer calories per portion.
Tanja Kral, who conducted the study as her master's thesis, said: "Some studies have shown that people take larger portions of foods labelled 'low fat' -using the label as a license to eat more. This study shows that energy density labels are unlikely to undermine the benefits of offering foods with fewer calories per ounce."
Kral conducted the study under the direction of Dr Barbara Rolls, who holds the Guthrie Chair of Nutrition in Penn State's College of Health and Human Development. Rolls noted: "This tendency of people to take the same size serving of less energy dense foods, even when they know the portion contains fewer calories, offers food manufacturers and restaurants a way to decrease the fat and calories in their products - making them healthier and satisfying."
The study is described in the October issue of the journal, Appetite, in a paper, "Does Nutrition Information About the Energy Density of Meals Affect Food Intake in Normal-Weight Women?"
In the study, 40 healthy, normal weight women aged 18 to 32, ate breakfast, lunch and dinner in Penn State's Laboratory for the Study of Human Ingestive Behavior on three days each a week apart. They ate the same meals each time: apple bake crisp for breakfast; pasta salad with yoghurt dressing for lunch; and an Italian pasta bake for dinner. However, the number of calories per ounce of food, or energy density, was changed on each day by varying the amount of apples in the apple bake crisp and the vegetables in the other meals to create low, medium and high energy density meals. The women rated the meals all equally palatable regardless of energy density.
Twenty of the women were given an energy density training session and a quiz that showed that they understood the concepts. These same women were given their meals with a label that said whether the main entree was low, medium or high in energy density, the actual value of energy density and the weight and calories per serving.
The other 20 women received no training or labels. Analysis of the women's eating behaviour showed that the pattern of food intake across the different levels of energy density was similar in the two groups when nutrition information was provided and when it was not.
In addition, the women in both the information and no information groups, consumed about 22 per cent fewer calories when their meals were of low energy density than when they were of high energy density.