Are work intensity and healthy eating substitutes? Field evidence on food choices under varying workloads

The strength model proposes that self-control is a constrained resource whose effectiveness tends to dwindle when an individual attempts to resist multiple sources of temptation at a time. We develop an economic framework for the strength model, and test its consequences in the field by analyzing the appeal of various food types by university students who face time-varying academic self-control demands. Our study utilizes both empirical analysis of actual university-wide transactions data, and a field survey approach with a real snack choice task. Compared to cafeteria purchases, purchase of less healthy fast foods increases during the week of final exams when students’ workloads are most cognitively demanding, compared to the purchase ratio of food sources during other times of the year. Helping to rule out alternative explanations, in the field survey the main robust and significant predictor of choosing an unhealthy snack over a healthy snack is subjects’ self-reported time needed to complete their academic responsibilities during the upcoming week. As combined evidence, these findings are consistent with an economic model of limited self-control in which students choose how to allocate their self-control between academic activities and eating activities. Under such a framework, the overall effectiveness of policies designed to help individuals make beneficial choices in a specific domain could be in practice, adversely affected by limited self-control capacities.