Diminishing Marginal Utility of Food Consumption for Healthy, Overweight and Obese Individuals
The concept of diminishing marginal utility may offer insight into the growing epidemic of obesity in the United States. This relationship between quantity consumed and perceived utility is frequently introduced by drawing an analogy to food consumption. However, the marginal utility for food may differ between normal weight and overweight/obese adults. In this study, we examine the marginal utility curve for food in both normal and overweight/obese individuals.
In addition, an individual's perception of the healthiness of food may play a role in determining their marginal utility curve. We also investigate if hiding or revealing nutritional information can alter the marginal utility curve for normal weight and overweight/obese people.
Methods:
Study participants were seated in individual tasting booths isolated from researchers and other participants. Participants were asked to repeatedly eat samples of chocolate distributed through a window in the front of each tasting booth. Half of the study participants were randomly given nutritional information with the number of calories contained in the samples of chocolate. Along with each sample, participants were given a questionnaire to rate the perceived taste and their willingness to pay for each sample. After eating each sample, participants were asked if they wished to continue and then received another sample.
Perceived taste utility curves were constructed using number of samples eaten and taste perception score. The time between samples was measured and also taken into account. Both absolute and relative changes in perceived tastes were compared between healthy and obese individuals. Time series regression models were used to model perceived taste changes while controlling for patient characteristics.
Results:
A total of 294 individuals were included in this study, of which 158 had a BMI that was considered normal 84 had a BMI considered “overweight” and 55 had a BMI considered “obese.” Study participants ate between 2 and 51 pieces of chocolate with a mean and median of 12.1 and 10 pieces, respectively.
Men and individuals that were obese had significantly higher levels of perceived utility. On average, the rate at which perceived utility diminished was around .13 points (on a 10 point scale) per piece of chocolate consumed. The rate of decline was not different between normal, overweight and obese individuals. However, individuals that received nutritional information had significantly higher rates of diminishing utility. The rate at which perceived utility diminished was roughly 41% higher for individuals that received nutritional information than those who did not.
Conclusions
This study provides evidence that perceived utility of food consumption diminishes in a manner consistent with economic theory. Although obese participants had similar declines in perceived utility to non-obese individuals, obese participants tended to start with, and maintain, higher levels of perceived utility. These results offer a possible explanation for the link between overconsumption and obesity. Although nutritional information did not appear to alter an individual’s initial perceived taste, it did tend to lead to higher rates of diminishing marginal utility. These results can help inform policy approaches for nutritional-content labeling.