Offering larger sandwiches increases calorie consumption

It is quite obvious that over the past few decades portion sizes have increased in restaurants and fast-food establishments. This increase in portion sizes corresponds with the increase in obesity seen in the United States. It is important to substantiate the role between obesity and this variation in portion size.

Recently, investigators at Penn State University initiated a study to determine how varying the portion size of a unit food (a deli-style sandwich) affects intake at lunch. People tend to eat in units if they are offered pre-portioned food. Several lunch items, such as sandwiches and burgers are offered as pre-portioned units and in recent years, the portion size of these units has substantially increased. However, it is often possible to choose between several portion sizes. Therefore, the question addressed in this study was whether the size of the unit of a food affects intake and whether individuals' characteristics of consumers influence the response to portion size.

Seventy-five healthy, young adults (aged 20 yrs to 45 yrs) participated in this study. All subjects had a BMI of less than 40, were not dieting or training for an athletic event and were not taking medications known to affect appetite. Potential subjects were screened using height and weight and through the following screening questionnaires: the 26-item version of the Eating Attitudes Test, the Zung Self-Rating Scale, and the Eating Inventory. These tests were used to rule out abnormal eating thoughts or behaviors.

This investigation used a within-subject design with repeated measures. Subjects ate lunch at the lab one day per week for 4 wks. During the 4-week period, all subjects received each of the four sizes of sandwich: 6 in., 8 in., 10 in., and 12 in. Subjects were instructed to keep their meals and activity level consistent and to refrain from consuming alcohol on the evening prior to and the morning of each test day. There were also instructed to not consume food or caloric beverages for 3 hrs before and after each test meal. The proportion of ingredients in all sandwich sizes was kept the same. Along with the sandwich, subjects were served 1 L of water, 14 g of salted potato chips and a 5-gram chocolate mint. They were instructed to consume as much or as little of the sandwich and water as they desired, but they were required to eat the potato chips and mint in full.

The proportion size of the sandwich did significantly influence lunch intake in both men and women (P<.0001). Most individuals consumed the entire 6-inch sandwich. When served the 12-inch sandwich, compared with the 8-inch sandwich, females consumed 12% more energy (74 kcal) and males consumed 23% more energy (186 kcal). Despite these differences, ratings of hunger and fullness were not significantly different after eating the 12-inch and 8-inch sandwiches.

These results indicate that offering a larger portion size of a food consumed in a unit increases the energy intake at that meal without altering an individuals rating of hunger or fullness.

B. Rolls, L. Roe, J. Meengs, et al. Increasing the portion size of a sandwich increases energy intake. J Am Diet Assoc. 104:367-372 (March, 2003) [Correspondence: Barbara J. Rolls, PhD, Department of Nutritional Sciences, 226 Henderson Building, University Park, PA 16802-6501. E-mail: bjr4@psu.edu