The prevalence of obesity continues to be of great concern to both adults and children in the United States. A notable increase in obesity can be observed over the past 20 years. In 2007 only one state (Colorado) had a prevalence of obesity less than 20 percent. Thirty states had a prevalence equal to or greater than 25 percent; three of these states (Alabama, Mississippi, and Tennessee) had a prevalence of obesity equal to or greater than 30 percent.1
Many factors contribute to Americans’ growing waistlines, but one observation in particular cannot be overlooked: the incidence of obesity has increased in parallel with increasing portion sizes.2 In almost every eating situation, we are now confronted by huge portions, which are perceived as “normal” or “a great value.” This perception that large portion sizes are appropriate has created an environment of portion distortion.3 We find portion distortion in supermarkets, where the number of larger sizes has increased 10‐fold between 1970 and 2000.We find portion distortions in restaurants, where the jumbo‐sized portions are consistently 250 percent larger than the regular portions.4 We even find portion distortions in our homes, where the sizes of our bowls and glasses have steadily increased and where the surface area of the average dinner plate has increased 36 percent since 1960.5 Research shows that people unintentionally consume more calories when faced with larger portions. In addition, research also shows that portion distortion seems to affect the portion sizes selected by young adults and children for some foods.6 Consuming larger portion sizes can contribute to positive energy balance, which, over time, leads to weight gain and ultimately may result in obesity.
The phenomenon of portion distortion has the potential to hinder weight loss, weight maintenance, and health improvement efforts. Food and nutrition professionals must develop ways to “undistort” what people perceive to be typical portion sizes and help individuals recognize what is an appropriate amount to eat at a single eating occasion.7
1 Centers for Disease Control and Prevention. U.S. obesity trends: trends by state, 1985–2008. http://www.cdc.gov/nccdphp/dnpa/Obesity/trend/maps/index.htm. Accessed 4/29/09.
2 Schwartz J, Byrd‐Bredbenner C. Portion distortion: typical portion sizes selected by young adults. J Am Diet Assoc. 2006;106(9):1412–1418.
3 Wansink B, van Ittersum K. Portion size me: downsizing our consumption norms. J Am Diet Assoc. 2007;7(7):1103–1106.
6 Schwartz, Byrd‐Bredbenner. Portion distortion; and Lawhun SA, Starkoff B, Sundararajan S, et al. Influence of larger portion sizes on the diet of overweight children and adolescents. J Am Diet Assoc. 2008;108(9):A38.
7 Schwartz, Byrd‐Bredbenner. Portion distortion.