Our Work

Cell phone Intervention Trial for Young Adults (CITY)

Project Objectives

Trials in middle-aged adults indicate that weight loss can be achieved and sustained with frequent contact over a long period of time, frequent self-monitoring, social support and motivational counseling. However, it is unclear whether this strategy would work in younger adults. Based on life stage, cultural context, environmental circumstances, and marketing pressures, behavioral intervention may need to be substantially modified to be effective in young adults. Even more adaptation will be required for intervention to be effective in young adults from racial/ethnic minority groups. The intervention builds on prior evidence with innovations directed at increasing effectiveness in young adults. Using cell phones to deliver a weight control intervention in this age group has the potential to be engaging, enjoyable, practical, cost-effective, sustainable, and broadly disseminated. We propose a trial in which a highly innovative but more risky intervention based almost entirely on the use of cell phone technology and a second, more incremental innovation over traditional behavioral intervention are each compared to a usual care control group. We will recruit a diverse target population of overweight/obese, generally healthy young adults, comprising approximately 35 percent non-Latino Whites, 35 percent non-Latino Blacks, and 30 percent Latinos, to be randomized to:

1. Usual care control: Educational materials and information but no behavioral intervention;
2. Cell-phone intervention: similar education and knowledge as the control group, but thereafter a behavioral intervention will be delivered almost exclusively via cell phone, particularly using the self-monitoring and social networking features of this technology;
3. Personal contact with cell-phone enhancement: personal contact intervention enhanced by cell-phone for self-monitoring.

The post-randomization intervention period will last 24 months. The primary outcome is change in weight 12 months post-randomization; an important secondary outcome is weight change at 24 months. The formative phase will focus largely on technology/intervention development.

Project Outcomes


The 365 randomized participants had mean baseline BMI of 35 kg/m2. Final weight was measured in 86% of participants. CP was not superior to Control at any measurement point. PC participants lost significantly more weight than Controls at 6 months (net effect 1.92 kg [CI 3.17, 0.67], P=0.003), but not at 12 and 24 months.

Despite high intervention engagement and study retention, the inclusion of behavioral principles and tools in both interventions, and weight loss in all treatment groups, CP did not lead to weight loss, and PC did not lead to sustained weight loss relative to Control. Although mHealth solutions offer broad dissemination and scalability, the CITY results sound a cautionary note concerning intervention delivery by mobile applications. Effective intervention may require the efficiency of mobile technology, the social support and human interaction of personal coaching, and an adaptive approach to intervention design.


Department & School

Psychology and Neuroscience
Trinity College of Arts and Sciences



  • NIH-National Heart, Lung and Blood Institute


  • Duke University Department of Medicine

Project Status


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