The booming smartphone industry has spawned an enormous market in health-related mobile phone applications, with apps related to dieting making up about 12% of the market. The apps use persuasive systems design, direct and indirect routes that persuade users to change their behavior. In a new longitudinal study, collaborating with a Pittsburgh-based, nutrition-focused mobile health company, researchers examined the effects of two distinct features of diet-related apps. Each feature produced different outcomes, providing practical guidance to those designing apps of this kind.
The study was conducted by researchers at Carnegie Mellon University, Hofstra University, and the University of California (UC)-Irvine. It is published in the International Journal of Information Management.
"Diet-related apps reach a wide range of people, but we know little about their effects on users' eating behaviors," says Rema Padman, professor of management science and healthcare informatics at Carnegie Mellon's Heinz College, who coauthored the study. "Having a deeper understanding of these features is essential for both research and practice."
With smartphones' capability of constant connectivity and multimedia functionality, it is easy for diet-related apps to provide features that enable social connectivity. For example, putting users in contact with experts to receive proactive, personalized feedback or suggestions offers persuasion directly, while connecting users with peers to share and observe experiences provides persuasion indirectly. Yet despite the widespread use of these types of features, diet-related apps struggle to retain users.
Drawing on social norms theory, media richness theory, and social comparison theory, researchers examined how nearly 350 adults' health eating behaviors were influenced directly or indirectly via two socially delivered features over four months in 2014. The features were photo-informed expert feedback, which provided proactive, personalized feedback on users' meal photos provided by a dietician, and photo-based peer observation, which featured users' observation of others' shared meal posts on a photo-based social platform.
Photo-informed expert feedback increased app use and slowed users' disengagement over time. It also improved users' meal recording but did not influence their meal balance. This suggests that photo-informed expert feedback may be effective in sustaining self-monitoring among general consumers who value authoritative guidance even if it does not immediately translate into improvements in dietary balance.
In contrast, photo-based peer observation reduced engagement—primarily in relatively unhealthy eaters—and did not significantly affect users' food choices. This suggests that some people may be deterred by the relatively healthy norms of a photo-based peer-sharing environment.
"Other persuasive systems design strategies, such as gamification, goal setting, and self-monitoring, are focused on individuals, but peer-and expert-based persuasion involve interpersonal social interactions, and the dynamic nature of these social interactions can foster a kind of social contagion of health behaviors," explains Yi-Chin Kato-Lin, associate professor of information systems and business analytics at Hofstra University's Frank G. Zarb School of Business, who led the study.
Adds Vibhanshu Abhishek, associate professor of information systems at UC-Irvine's Paul Merage School of Business: "Understanding the causal impacts of these strategies is critical for advancing theory and informing the design of responsible digital health interventions."
Among the study's limitations, the authors note that the two features they studied were not perfectly symmetrical and therefore may not generalize to other expert or peer designs. In addition, participants were primarily young Android users in the United States with an interest in healthy eating, which limits the generalizability of the findings to other populations. Finally, the data were collected in 2014 and digital health technologies have evolved significantly since then.
"The features we examined reflect underlying patterns of human behavior that persist despite rapid technological changes," notes Julie Downs, professor of psychology and decision science at Carnegie Mellon. "Since our work reveals causal evidence on these behavioral mechanisms rather than on the performance of a specific app, it is relevant in the context of current digital efforts to improve health."
