An Examination of Individual Eating Behavior Characteristics Related to the Portion Size Effect
Open Access
- Author:
- Supplee, Hannah
- Area of Honors:
- Nutritional Sciences
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Barbara Jean Rolls, Thesis Supervisor
Alison Diane Gernand, Thesis Honors Advisor - Keywords:
- portion size
bite rate
eating patterns - Abstract:
- The portion size effect is a phenomenon that has been thoroughly investigated in previous research, showing that when individuals are presented with larger quantities of food, they tend to consume larger amounts in terms of both food and energy intake. With supermarkets and fast food restaurants increasing their portion sizes over time, this particular effect of larger portions has become of serious concern. However, there is a lack of consensus about what makes an individual more or less susceptible to the portion size effect. The overall goal of this study was to evaluate how specific eating patterns such as bite rate, bite size, meal duration, acceleration and deceleration of eating, and individual characteristics may be driving the portion size effect in the general population. Furthermore, the study includes a video analysis component to further assess the cumulative bite rate trajectories for each portion size condition as a more detailed, wholistic representation of bite rate. The study included 46 individuals (n=29 females) between the ages of 18 to 69 years with an average body mass index (BMI) of 25.4 kg/m2 for women (SD = 3.8) and 25.4 kg/m2 for men (SD = 3.9). On a scale of 0 to 21, women had an average dietary restraint score of 8.2 (SD = 5.2), while men had an average score of 9.2 (SD = 4.6). One day a week, for four weeks, each participant consumed one of four different portion sizes of macaroni and cheese ad libitum as a lunch meal. As portion size increased across all four portion size conditions, both energy and food intake significantly increased. More specifically, as portion size increased by 75%, energy and food intake increased by an average of 46% across all participants, while meal duration increased by 38%. According to the cumulative bite rate trajectories, there was a greater degree of deceleration of bite rate for the larger portion size conditions compared to the baseline condition. This finding highlights the idea that as individuals are served larger portions, they tend to take fewer bites over a longer period of time towards the end of the meal. Additionally, estimates of bite size indicated that there was a smaller count of large bites in the baseline condition compared to the three larger portion size conditions; this suggests that individuals tend to take more large bites when served increased portions. Finally, dietary restraint was found to negatively correlate with average calculated bite rate across all four portion sizes, though the association did not reach statistical significance. However, this finding still suggests that with a larger subject population, individuals with greater dietary restraint likely trend towards having slower bite rates during their meal. Overall, this study found that meal duration, deceleration of bite rate at the end of the meal, number of bites as a whole, and number of large bite sizes consumed were some of the significant predictors of increased individual susceptibility to the portion size effect. This study also found practical value in using video coding of ingestive behavior to track estimated bite size and cumulative bite rate across a meal. Future weight loss programs should focus specifically on education around controlling intake when presented with larger portion sizes, in addition to how eating behaviors such as decreasing bite size and frequency may be adjusted for appropriate intake. As a result, individuals should have a greater awareness of their eating behaviors in a way that will help to prevent over-consumption when presented with larger portion sizes.