Does Portion Size or Amount of Food Affect Consumption?
Food Size and Eating Less
Snacking on foods packaged as individual servings does not appear to lead people to eat less than eating the same food out of a large bag. This suggests that the total amount of food available, not the package or portion size, provides the cue for how much to eat.
"Consumers might think they will eat less by purchasing pre-packaged quantities of individually sized snacks rather than one bigger bag or box. However, our study suggests this is not the case," said Hollie Raynor, Ph.D., R.D., assistant professor of research at Brown Medical School and Miriam Hospital in Providence, RI. "Additionally, portion-controlled packages are often more expensive than large packages."
In the study, 28 healthy, college-aged, non-obese volunteers who were not dieting or trying to lose weight were randomly assigned one of four boxes of snack foods (potato chips,cookies, cheese crackers and candy) with either large or small portions and a large or small total amount of food. The four box conditions were single-serving bags totaling 4,350 kcal or 8,750 kcal, or large portions (at least five times the size of the single-serving size) totaling 4,350 kcal or 8,750 kcal. Thus, participants in the two small amount conditions received the same amount of food, but it was packaged differently, and the same was true for the two large amount groups.
Participants took the food home, ate as much or little as they wanted and brought back any remaining food after three days.
The results showed that all participants ate approximately 60 percent of what was given to them, regardless of how it was packaged. The subjects who took home the 4,350 kcal boxes ate the same total amount of snack food over three days whether the food was packaged as individual servings or as large bags. The same was true of the two groups receiving the 8,750 kcal boxes.
Additionally, the two groups with the large amount of food consumed about 80 percent more energy over the three days, an average of 5,028 kcal vs. 2,782 kcal for those who got the smaller total amount of food. These findings indicate that smaller portions did not influence how much to eat. Rather, the total amount supplied suggested the appropriate amount.