Effect of plate size on appetite and energy intake: a postprandial study of appetite regulation

Abstract

The study of appetite has generated increasing interest over the past few decades and is believed to play an important role in the obesity epidemic faced worldwide today. Obesity occurs as a result of energy imbalance over time, with energy intake greater than energy expenditure. Energy intake comes from food intake and thus the regulation of food intake and appetite is critical to control of body weight. Decreased portion size as well as eating from a smaller plate is frequently recommended as a strategy to decrease food intake. Very few studies have investigated the effects of plate size on energy intake and those studies have mixed results. Some studies showed that altering plate size did not affect energy intake while other studies showed an association with a change in energy intake when foods were served into different size containers or bowls. Thus, more investigation is required in this field. The aim of this study was to determine whether altering the size of dining plate from which a group of overweight women ate would affect ad libitum (free choice) food intake from a buffet-style lunch meal. The hypothesis was that larger plate size would result in an increase in food intake. This was a two treatment cross-over study where 20 overweight (BMI 29.7±4.5 kg/m2) women attended the University of Auckland Human Nutrition Unit on two occasions. They were unrestrained eaters, able to eat to appetite and not currently dieting. Participants were fasted prior to a breakfast meal, and were randomly assigned to either small (19.5cm) or large (26.5cm) dining plate on to which they served themselves from the lunch meal. Participants were given a light (0.5MJ) breakfast at 9am and were required to stay in the unit with access to no other food until the lunch meal. They were then asked to eat to appetite (ad lib) at an outcome lunch meal at 12 noon. Throughout the day, appetite sensations were measured using visual analogue scales (VAS). Food items were weighed before and after lunch to calculate energy and macronutrient intake of the ad lib meal. 21 overweight women were registered into the trial and 20 completed the study. There was no detectable difference in VAS-assessed appetite ratings following the breakfast meal on each of the two visits (P>0.05), which confirmed that participants were in a similar state of hunger/fullness prior to the lunch meal, and was as expected following 2 identical breakfast meal. Mean (SEM) energy intake at lunch using the small and large plates was 3975±26.7 and 3901±27.8 kJ respectively. There was no detectable decrease in energy and macronutrient intake when the large plate was replaced by small (paired t-test, P>0.05). In this study, dining plate size did not affect ad lib food intake from a multiple item buffet-style lunch in overweight women. This reinforces with several previous plate size. Despite this, the recommendation to use a smaller plate as a cue for weight control in the overweight should not be ruled out. This study and other previous studies have all focused on participants that are willing to eat freely. If the same study was repeated on a different group of people, such as women who were consciously trying to lose weight and hence actively restricting intake, it is possible that a smaller plate may help in restricting intake. Thus more research is needed to find out whether the use of smaller plates can be used as a way to lower food intake in individuals actively trying to diet, and therefore recommendation for prevention or treatment of obesity. Future studies should address this research question.