Unintended consequences in traffic-light food labeling: A call for mixed methods in public health research.

Nudge theory describes how indirect suggestions and positive reinforcement can influence decision-making. We used nudge theory to implement a traffic-light labeling and choice architecture (modifying product placement) intervention at Harvard University cafeterias, but found no significant change in sales. Survey and focus group data showed that some students thought the labeling may exacerbate eating disorders, however, there is extremely limited research on potential negative consequences of labeling. One way to describe these findings is through 20th century philosopher Michel Foucault's concept of biopower. Biopower manipulates cultural norms and nudges individuals to engage in self-surveillance and self-discipline, de facto subjugating themselves to certain ways of being. Biopower may lead to the creation of an in-group and an out-group based on who can adopt the new behaviors, such as healthy eating. Those in the out-group may face additional unintended consequences, highlighting the need for mixed-methods research to better evaluate public health interventions.