Health behavior change interventions delivered over the Internet or other computer-based channels of communication are increasingly available. Recent evaluations of some interventions that use these channels indicate that they have the potential of combining the low cost and reach of public health interventions and the effectiveness of interventions delivered by health professionals. Yet few Internet and other computer-based interventions have been rigorously evaluated, and no studies have compared the efficacy of interventions delivered over different technology-based communication channels. We plan to conduct a study (1) to determine the competitive advantage of different automated communication channels for delivering a standardized dietary behavior change intervention for reducing cardiovascular disease risk and (2) to advance understanding about behavior theory constructs and communication channel characteristics that might be associated with intervention utilization and efficacy. To do so, we will compare totally automated, population-based tailored (1) print, (2) telephony, and (3) Web interventions for promoting dietary behavior change. These interventions will use the same behavioral theoretical structure (the Transtheoretical Model) and similar content, designed to reduce cardiovascular disease risk by promoting intake of fruit and vegetables and reducing consumption of saturated fat. Each of these three interventions have been shown to be efficacious compared to no intervention control conditions in randomized clinical trials. We will recruit 2,240 study subjects with high saturated fat and low fruit and vegetable intake from a list- assisted national random digit dial sample. They will be randomly assigned to four study groups (560 per group): (1) control (which will receive an informational booklet on healthy eating), (2) tailored print (PRINT- DIET), (3) tailored telephony (Telephone Linked Communication [TLC-DIET]), and (4) tailored Web (WEB- DIET). For each study subject, the intervention period will be 12 months, followed by a 12-month observation period to assess maintenance of intervention effects. For this study, we will develop a new instrument to assess the users'evaluation of the effectiveness of the channel of communications used by the intervention they received (print, telephony or Web). The instrument will focus on eight communication dimensions identified by Salmon and Atkin (2003). We will evaluate each of the three interventions compared to the control condition and to each other regarding their effects on the two dietary outcomes at 12 and 24 months follow-up. We will also investigate whether specific constructs from behavior change and communications theories explain use of the three interventions and their effects on dietary behavior outcomes.
