This study demonstrated that participants who used a PR, a PDA with dietary and exercise software or a PDA with the same software and a daily, tailored feedback message achieved significant weight loss at 6 months. A higher proportion of the PDA+FB group achieved a ≥ 5% weight loss than the PR and PDA groups, suggesting that the daily tailored feedback messages may have enhanced the effect of standard behavioral weight loss treatment. Overall, the weight loss was good in all 3 groups, which might be explained by the frequent group sessions during the first 6 months. The attention and guidance received through the standard behavioral intervention facilitated weight loss across all groups and thus the difference by method of self-monitoring was less pronounced than what was expected. We also demonstrated that those in the PDA and the PDA+FB groups were significantly more adherent to self-monitoring than those in the PR group. While the findings do not support our hypothesis that the PDA+FB group would be more adherent to self-monitoring than the PDA group, they do support our hypothesis that the groups who used a PDA would be more adherent than the PR group.
This was the first large randomized clinical trial to compare different methods of self-monitoring in a behavioral weight loss intervention and to compare the use of PDAs to conventional paper diaries. Two previous studies addressed self-monitoring methods and reported a significant association between the number of diaries completed and weight loss; however, neither of them reported a group difference in weight loss (20
). Because of the methodological limitations in both studies, one cannot definitively conclude that approaches to self-monitoring other than the use of paper diaries result in better adherence or weight loss outcomes. However, our findings from this randomized trial with excellent retention do provide preliminary data to suggest that there is improved adherence to self-monitoring with the use of a PDA.
Tate and colleagues reported previously on a weight loss study that used a feedback system (12
). While the group receiving the automatic computer feedback messages was comparable in weight loss to the human e-mail counseling group at 3 months; at 6 months, the e-mail counseling group had significantly greater weight loss than the computer-automated feedback group or no counseling group. The main difference between that study and our trial is that the computer feedback message in their study was delivered on a weekly basis and our PDA-delivered feedback message occurred daily (16
). The significantly greater weight loss in our PDA+FB group suggests that the combined self-monitoring and feedback message delivered in real-time and on a daily basis might have provided the reinforcement and sustained motivation that was needed to improve weight loss.
The findings supported the difference in adherence to self-monitoring between the combined PDA groups and the PR group but the adherence in the two PDA groups was similar. As can be seen in , the slope of the adherence curve began to decline at 3 weeks and steadily declined thereafter with only 30% of the PR group self-monitoring at 6 months. However, adherence for the two PDA groups was sustained by over 70% of the participants in these groups until the 12th
week. At 6 months, it was still above 50%. This decline in self-monitoring over time has been a consistent finding in several studies (12
). The decline that we observed in this study is slightly less than what we observed in a previous trial (23
) and most important, the decline in the PDA groups was significantly less than what was observed in the PR group.
While the study demonstrated that the use of the PDA improved adherence to self-monitoring in both groups (90% in PDA+FB and 80% in PDA), it was unclear why the improved adherence in the PDA without feedback group did not lead to a greater weight loss than what we observed. This may suggest a more central role for individualized feedback to goal attainment. This finding is consistent with the behavioral principles that document that feedback, both reinforcing feedback and corrective or redirective feedback, enhances motivation toward goal attainment. The feedback message functioned as a compass that enabled the individual to stay on course toward the goal; it also functioned as a source of more frequent attention that `someone' was noticing what the participant was doing, which was another powerful reinforcer, regardless of the nature of the feedback.
The goal of teaching an individual to self-monitor is that the person will learn to use the tool to provide information (feedback), and will use the information to self-correct behaviors (e.g., eating or food intake). However, many individuals do not make that connection easily, which probably contributes to their stopping self-monitoring, since they never used the strategy in a way that made a difference or sense to them. The addition of a programmed, tailored feedback message may have helped them make that connection (24
Our findings showed that the participants in the PR group were consistently less adherent to self-monitoring over the 6 months. This might have been explained by the disadvantages to using a PR (25
). Individuals who use a PR are faced with the labor of maintaining handwritten records, searching for the nutrient composition of foods in a pocket manual, and calculating subtotals for nutritional intake. In a previous study of participants who used PR, participants reported that self-monitoring was often time-consuming and burdensome (26
), which often led them to record at the end of the day or days later (27
). This practice eliminated the opportunity to take corrective action if one was close to the daily energy or fat goal. In contrast, benefits of using the PDA included its portability and immediate access to a U.S. Dept. of Agriculture database containing 5000 to 6000 food items including brand and restaurant foods, real-time calculation and display of dietary subtotals in relation to daily goals, and saving commonly eaten meals. Participants reported that its use was socially acceptable and thus reduced the uneasiness that might have accompanied self-monitoring in social settings. Finally, advances in wireless technology now permit transmittal of monitoring and feedback, which provide opportunities for intervention delivery (28
There could be limitations to using a PDA. Use of technological devices might have been a barrier for some individuals; however, participants who were technologically naive were able to learn how to use the device. It is still unclear if a person saves time with a PDA (19
), as this may vary depending on the software being used and the screen design.
The major strengths of our study included the randomized trial design with objective measures of the anthropometric measures and its innovative approach to examining the use of a technology that is becoming ubiquitous. It was the first large trial to compare the efficacy of PDAs with combined diet and exercise software to the traditional PR in improving weight loss and adherence to self-monitoring. An additional strength was our 91% retention rate at 6 months and the 21.4% minority representation. An important limitation was that we achieved only 15.2% male representation despite extra efforts that were made to recruit men. Additionally, the study design was for a 24-month final testing of the hypothesis; the results presented here were for 6 months and thus only revealed the short-term outcomes.
In summary, in our study that used 3 different approaches to self-monitoring diet and exercise, each group achieved a significant weight loss. Moreover, a higher proportion of the PDA+FB group achieved a clinically significant weight loss (5%) than the PDA and PR groups. The daily tailored feedback appears to have enhanced the effect of the behavioral treatment. Our study revealed that a significantly greater proportion of participants in the PDA and the PDA+FB groups self-monitored compared to those in the PR group. Also, there were significant within and between group differences in waist circumference and energy intake at 6 months. These findings suggest that use of an electronic diary facilitates improved self-monitoring; however, the use of an electronic diary plus a daily feedback message that was tailored to what had been entered in the diary was related to the best weight loss.