Food, Fun and Fitness Internet program for girls: influencing log-on rate

Internet-based interventions hold promise as an effective channel for reaching large numbers of youth. However, log-on rates, a measure of program dose, have been highly variable. Methods to enhance log-on rate are needed. Incentives may be an effective method. This paper reports the effect of reinforcement schedule and recruitment method on log-on rates to an 8-week Internet-based obesity prevention program. It also explores trends in log-on rate. Girls were randomized to receive immediate (weekly) or delayed (program end) incentives ($5). The study was powered to detect a moderate-to-large effect (0.65). Overall log-on rate was 74.5%. A higher but not statistically different log-on rate was observed in the immediate incentive group (79%) than in the delayed incentive group (70%) (P = 0.118), and among girls recruited via media (80%) as opposed to non-media methods (69%) (P = 0.058). Trend analysis indicated a significant drop in log-on rate between weeks 4 and 5 among all participants (P = 0.009). Although an acceptable log-on rate was achieved in this program, there was a substantial drop between weeks 4 and 5. Identifying the reason that this occurred may provide insight into how to further enhance log-on rate. Recruitment method may influence log-on rate.