Background: Limited evidence exists on long-term efficacy of interactive computer-tailored interventions for increasing physical activity and decreasing fat intake, and even more so when they are implemented simultaneously or sequentially.
Purpose: This study aims to examine long-term efficacy of interactive computer-tailored physical activity and fat intake interventions, and evaluate their efficacy in a simultaneous or sequential implementation over 2 years.
Methods: Participants (392) were randomly assigned to a simultaneous group receiving both interventions at baseline; a sequential group first receiving the physical activity intervention and 3 months later the fat intake intervention; and a sequential group first receiving the fat intake intervention and 3 months later the physical activity intervention.
Results: Strong time effects were seen for total physical activity (F = 38.7, p < .001) and fat intake (F = 103.9, p < .001), indicating that intervention effects remained over 2 years for those participants that were still available for the 2-year follow-up. At 2-year follow-up the interventions resulted in a 10% and a 27% increase of participants that met public health recommendations for physical activity and fat intake, respectively. Overall the interventions were more effective for participants not meeting the public health recommendations at baseline. The sequential intervention mode was overall slightly more effective than the simultaneous mode in maintaining intervention effects.
Conclusions: Both interventions showed efficacy in maintaining long-term health behavior changes. More research is needed on sequential and simultaneous intervening modes.